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Q&A Webinar After Uncategorized

Operational and Embodied Carbon, Together at Last! The MA 100-Home Embodied Carbon Study

Patrick Nachlas & Andy Buccino, joined us recently for our  Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or want to share it with a friend or colleague, you can now do so, as the recording and an article on the topic are available below. 

The webinar helped attendees understand the crucial difference between embodied carbon (EC) and operational carbon in home construction, emphasizing that while Embodied Carbon is not currently part of the HERS (Home Energy Rating System), it is a significant contributor to a building’s overall carbon footprint—often exceeding yearly operational emissions. Participants learned that materials such as concrete and insulation play a major role in EC, and that new tools, standards, and Environmental Product Declarations (EPDs) are making it more feasible to measure and reduce embodied emissions. The session highlighted that addressing both operational and embodied carbon is essential for a comprehensive approach to sustainability, and revealed that the payback time for EC in new homes can be substantial, leading some to view renovation as a greener option. Many found it eye-opening just how large the EC impact can be, and appreciated real examples, regional differences, and practical methods for incorporating EC into future rating systems.

Please help us keep these webinars and writings going by becoming a supporting GHI member or by making a donation. 

As the focus of sustainable building practices shifts from operational efficiency to a holistic view of a building’s carbon footprint, embodied carbon has emerged as a critical consideration. This article explores the findings and methodology of the Massachusetts 100 Home Embodied Carbon Study, which benchmarked embodied and operational carbon in new residential construction. The study demonstrates how HERS raters and energy modeling professionals can integrate embodied carbon assessment into existing workflows, identifies key carbon drivers in building materials and processes, and discusses how these insights are shaping incentive structures and policy in Massachusetts and beyond. The article is intended for housing professionals, builders, contractors, and the general public who are interested in the future of low-carbon construction.

Introduction: Moving Beyond Operational Carbon

For decades, the primary focus of carbon mitigation in the building sector has been on operational carbon—the emissions generated by heating, cooling, lighting, and powering homes. This emphasis has been driven by tangible benefits such as lower utility bills and improved comfort, and it has led to remarkable gains in energy efficiency through programs like HERS ratings, Passive House standards, and the pursuit of net zero energy homes.

However, as operational carbon is steadily reduced thanks to more stringent codes, electrification, and the decarbonization of electricity grids, a new challenge emerges: the carbon emissions associated with the production and assembly of building materials—the so-called “embodied carbon.” Unlike operational emissions, which accrue over decades, embodied carbon is released up front, before a new homeowner ever switches on a light. These upfront emissions are rapidly becoming a dominant factor in the overall climate impact of new construction.

The Massachusetts 100 Home Embodied Carbon Study was designed to quantify and analyze both operational and embodied carbon in residential projects, providing the first comprehensive North American benchmark that integrates mechanical, electrical, and plumbing (MEP) systems into the embodied carbon calculation. The study’s methodology, findings, and implications offer vital guidance to professionals seeking to address the full lifecycle emissions of homes.

Understanding Embodied Carbon: Scope and Significance

Embodied carbon refers to the greenhouse gas emissions generated throughout the lifecycle of building materials, from resource extraction and manufacturing (cradle) to delivery at the construction site (gate). In the context of lifecycle assessment (LCA), this is typically designated as stages A1-A3. These emissions include the processing of concrete, steel, wood, insulation, and other materials, as well as their transportation and initial installation.

While operational carbon (stage B6) remains important, data from the study confirms that embodied carbon constitutes a significant share of a building’s total emissions. For the average home in the Massachusetts study, approximately 55.5 tons of CO2-equivalent were emitted before the first occupant moved in. By comparison, annual operational emissions for these homes were about 3.1 tons, meaning it takes nearly 18 years of operation to match the carbon footprint incurred during construction.

Globally, embodied carbon accounts for roughly 9% of building-related emissions—a figure that is rising as operational emissions fall due to advances in energy efficiency and the growth of renewable energy. In the U.S. alone, annual embodied emissions from new residential construction are comparable to the total emissions of entire countries such as Austria or Greece.

Why Embodied Carbon Matters Now

The urgency of addressing embodied carbon stems from the time value of emissions. Upfront carbon is released immediately, contributing to atmospheric greenhouse gas concentrations when mitigation is most critical. Delaying action on embodied carbon risks overshooting near- and mid-term climate goals—even as buildings become more efficient in their operation.

Moreover, as codes and practices drive operational emissions downward, embodied emissions become the “next big bar on the chart”—the next frontier for meaningful carbon reduction in the built environment. Builders, designers, and contractors who understand and act on this challenge will be leaders in the evolving landscape of sustainable construction.

Methodology: Integrating Embodied Carbon Assessment into Residential Practice

The Massachusetts study was groundbreaking in several respects:

  • It centered HERS raters as the key workforce for embodied carbon assessment, leveraging their existing expertise in building science and energy modeling.
  • It integrated MEP systems into the embodied carbon calculation, providing a more complete picture of total building emissions.
  • It aligned its methodology with the newly released RESNET 1550 standard, which establishes protocols for embodied carbon data collection and reporting in the residential sector.

Data Collection and Analysis Workflow

Participation in the study was limited to dwelling units registered with RESNET and built between 2023 and 2024 in Massachusetts—a state where over 90% of new homes undergo HERS rating. To streamline the process, the study team developed an “integration sheet” that allowed data from energy modeling software (such as Ecotrope) to be efficiently transferred into BEAM, a free embodied carbon calculator.

HERS raters were trained to supplement their usual data collection with additional inputs needed for embodied carbon analysis, such as material quantities for foundations, partitions, and garage areas that are typically omitted in standard energy models. The study found that approximately 60-70% of the data required for an embodied carbon assessment is already captured during a typical HERS rating, making the additional workload manageable after initial training.

To quantify the emissions associated with each material, the study relied on Environmental Product Declarations (EPDs)—third-party verified documents that specify a product’s global warming potential per unit of measure. Where product-specific EPDs were not available, industry-average values were used.

Key Findings: Embodied Carbon Baselines and Drivers

  1. Average Embodied Carbon: The average upfront embodied emissions for the 100 homes studied was 55.5 tons of CO2e per dwelling. This figure provides a crucial baseline for future policy, incentives, and design improvements.
  2. Operational vs. Embodied Carbon: With operational emissions averaging 3.1 tons per year, the initial 55.5 tons of embodied emissions represent a substantial “carbon debt” that takes nearly two decades to offset through efficient operation.
  3. Variability and Opportunity: The study observed a wide range of embodied carbon results, from as low as 20 tons to as high as 144 tons per home. This variation indicates significant opportunity for reduction through material choices and design optimization.
  4. Key Material Contributors: Concrete emerged as the single largest contributor, responsible for about 40% of embodied emissions, followed by MEP systems (18%) and insulation. Windows, while significant in commercial buildings, were less impactful in the residential context studied.
  5. MEP Systems: The inclusion of MEP systems in the embodied carbon scope is notable. While energy models can often estimate heating and cooling equipment based on capacity and duct area, some components (such as wiring) must be approximated by building size to avoid excessive data collection burdens.
  6. Intensity Metrics: When normalized by building size, the average embodied carbon intensity was approximately 226 kilograms CO2e per square meter, consistent with similar studies in North America.

Workflow Feasibility: Training and Quality Assurance

The study’s approach to integrating embodied carbon assessment within the existing HERS workflow was validated by the experience of 16 raters, whose average time to complete an embodied carbon assessment dropped from over three hours to less than one hour as familiarity increased. While early projects required more effort—especially for homes rated months or years earlier—the expectation is that real-time assessment in tandem with operational ratings will further reduce the burden.

ResNet’s emerging quality assurance protocols for embodied carbon will help ensure data consistency and reliability, mirroring the success of HERS as the “gold standard” for operational energy assessment.

Implications for Policy and Market Transformation

Massachusetts is already embedding embodied carbon reduction into its building code and incentive structures. Builders can earn HERS point adders for using low-carbon concrete or achieving a low-carbon shell, effectively trading modest increases in energy efficiency for substantial carbon reductions in materials. This approach recognizes that embodied and operational carbon are distinct but complementary, and that both must be addressed to achieve true decarbonization.

The study’s findings provide a defensible baseline for policymakers to set targets, utilities to design incentives, and builders to benchmark their performance. As the market for low-carbon materials matures and the integration of embodied carbon assessment becomes routine, substantial reductions are within reach.

Looking Ahead: The Path to Holistic Carbon Accounting

The Massachusetts 100 Home Embodied Carbon Study demonstrates that embodied carbon assessment is both feasible and impactful in the residential sector. By leveraging existing energy modeling infrastructure and workforce, the additional burden is minimized, and the path is paved for rapid adoption as software tools evolve.

The study also highlights the need for clear metrics, robust data, and ongoing training. As embodied carbon becomes embedded in codes, incentives, and green building certifications, builders and contractors will be increasingly called upon to make material choices that balance performance, cost, and climate impact.

The ultimate goal is a holistic carbon index that integrates both operational and embodied emissions, allowing for true “low-carbon” certification of new homes. While this remains a work in progress, the groundwork has been laid for the residential construction industry to play a leading role in climate action.

Key Takeaways

  • Embodied carbon now represents a substantial share of the total carbon footprint of new homes, especially as operational emissions decline.
  • The Massachusetts study provides the first North American embodied carbon baseline that includes MEP systems for residential construction.
  • On average, new homes in the study emitted 55.5 tons of CO2e upfront, with operational emissions of 3.1 tons per year.
  • Concrete is the largest single source of embodied carbon in residential construction, highlighting the importance of low-carbon material alternatives.
  • Approximately 60-70% of data needed for embodied carbon assessment is already collected during standard energy modeling, making integration feasible.
  • Incentives and policy are beginning to recognize embodied carbon, with Massachusetts offering HERS point adders for low-carbon materials.
  • Builders, contractors, and energy professionals will need ongoing training and quality assurance protocols as embodied carbon assessment becomes standard practice.
  • The future of sustainable construction depends on addressing both operational and embodied carbon in a holistic, data-driven manner.

 

Q: Who is updating assumptions on carbon content as production methods improve?
A: The RESNET Carbon Index uses NREL data and assumptions on grid cleanliness over the next 25 years. You can read more about it here.

Q: Is foam an insulation issue versus airtightness in fiberglass properly accounted for?
A: It is not a direct tradeoff. There are many methods to airseal a home. Infiltration rates are accounted for in the operational emissions.

Q: How do ICF homes fare in EC compared to stick-framed homes? Will “green” concrete made from electrochemical/solar electricity cement cut down on its EC contribution in a meaningful way?
A: This was not part of this study. However, we would anticipate any meaningful reduction in embodied concrete emissions would have a substantial impact in the whole home results.

Q: Shouldn’t operational carbon vs embodied be compared “apples to apples”? As shown on the previous slides, the type of building affects the results. Putting all the numbers together might be misleading.
A: No, they are disconnected decision trees. The embodied carbon of the materials selected in a home does not directly correlate to the energy efficiency of the home.

Q: Would this study and EC rating methods be instructive on preserving existing structures (for improved reuse) instead of teardowns, which add yet more carbon?
A: End of life for existing buildings was not included in this study.

Q: What was different in components between high and low embodied carbon projects?
A: Amount of concrete and type of insulation were the two primary contributors.

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Uncategorized

How Property Data Can Help Identify Hidden Risks Before You Invest in a Home

Written by SEENE

A home can look move-in ready and still be sitting on top of problems no walkthrough will ever reveal. A previous unpermitted addition, a lien nobody mentioned, an elevated radon reading in the basement, none of these show up on a standard showing, and by the time they surface, the buyer usually already owns the house. The visible condition of a property and its actual history are two very different things, and only one of them is on display during an open house.

That’s the gap property data is built to close. Instead of relying on what a listing photo or a single walkthrough can tell you, buyers now have access to records that reveal what’s actually happened to a property over its lifetime, not just how it looks today.

What a Walkthrough Can’t Tell You

A real estate agent showing a home is working from the same visible surface every buyer sees: fresh paint, staged furniture, a tidy yard. What that showing won’t reveal is whether a past renovation was permitted, whether the seller has an outstanding lien against the property, or whether the home sits in a flood zone that isn’t obvious from the street.

These aren’t rare edge cases. Permit history, ownership records, tax history and zoning details all exist in public records, but they’re scattered across different city and county systems that most buyers never think to check before making an offer, and few agents have the time to pull every record manually for every showing.

Where Property Data Platforms Fill the Gap

This is exactly the kind of research PropertyShark is built for, consolidating property records, ownership history, tax and sales data, and risk maps into a single report rather than requiring a buyer to track down permit records from one office and lien filings from another. For a buyer trying to understand a property’s actual history before committing to it, that consolidation turns a multi-day research task into something achievable in an afternoon.

Seeing a property’s full record before an offer is submitted changes the negotiation, too. A buyer who knows about an unresolved permit issue or a prior violation has leverage to ask for a price adjustment or a repair before closing, rather than discovering the problem after they already own it.

Environmental Risk Is Often the Least Visible Risk of All

Some of the most consequential risks in a home are the ones with no visual trace at all. Radon is the clearest example: the National Cancer Institute estimates that about 1 in 15 U.S. homes has a radon level at or above the EPA’s action level, a gas that’s completely undetectable without testing and is the second leading cause of lung cancer in the country after smoking.

Public property data can flag some environmental risk factors, flood zone designation, proximity to known contamination sites, but it doesn’t replace an actual inspection or radon test. It narrows down which properties deserve that closer look before a buyer gets emotionally, and financially, attached.

Where GreenHome Institute Fits Into the Picture

Property data and green building certification answer different but related questions. Data can tell a buyer what’s on record for a property; it can’t tell them how efficiently the home actually performs or whether it meets a recognized sustainability standard. That’s where a GreenHome Inspection comes in, evaluating a home’s health, energy performance and sustainability features directly, the kind of on-the-ground assessment that complements what property records can show from a distance.

Used together, the two approaches cover more ground than either does alone: public records surface legal, financial and environmental red flags, while a physical inspection confirms how the home is actually built and performing today.

Making Property Research Part of the Process, Not an Afterthought

The buyers who avoid the most expensive surprises aren’t the ones who got lucky. They’re the ones who treated property research as a standard part of due diligence rather than something to worry about only if a red flag happens to surface during a showing. Pulling ownership, permit and tax records earlier in the process, alongside a proper inspection, turns hidden risk into something a buyer can actually see and price in, before signing anything.

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Q&A Webinar After Uncategorized

HVAC Filter Change Alerts Ignored No more? DIY Smart Filtration is Here Article

Winston Mok, joined us recently for our  Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or want to share it with a friend or colleague, you can now do so, as the recording and an article on the topic are available below. 

During the webinar, attendees learned about the importance of using high-efficiency air filters (such as MERV 13 or higher) to capture fine particulate matter like PM2.5, which can have significant health impacts if not properly managed. Many participants gained a better understanding of how indoor air quality (IAQ) can often be worse than outdoor air, and that filter appearance alone is not a reliable indicator of filter effectiveness or need for replacement. The session highlighted how filters, even when they look clean, might be clogged and negatively impact air flow and HVAC system performance. Attendees appreciated the clear explanations of MERV ratings, regulatory requirements like California performance labeling, and the relationship between filtration, air flow, and health.

Please help us keep these webinars and writings going by becoming a supporting GHI member or by making a donation. 

Maintaining high indoor air quality is essential for both the health of building occupants and the longevity of residential HVAC systems. This article explores the importance of dynamic, smart filtration systems as an evolution beyond traditional static filter schedules. Drawing on a comprehensive presentation by an industry expert, the discussion covers the science of particulate matter, filtration standards, the technical challenges of modern airtight homes, and the real-world performance of smart filtration. The intended audience includes housing professionals, builders, contractors, and the general public interested in sustainable, healthy living environments.

Introduction: The Overlooked Cornerstone of Healthy, Efficient Homes

The greenest home is only as healthy as the air its occupants breathe and the systems that support it. While design, construction materials, and energy efficiency often receive primary focus in sustainable housing, ongoing operations and maintenance—particularly regarding air filtration—are fundamental to realizing the benefits of these investments. With the rise of tighter building envelopes and increasing awareness of indoor air quality (IAQ), the paradigm is shifting from fixed filter replacement schedules to dynamic, responsive smart filtration systems.

The Challenge of Airtightness and Indoor Air Quality

Contemporary building practices emphasize airtight construction to maximize energy efficiency. While this approach is effective for controlling thermal losses and gains, it inadvertently compounds IAQ challenges. Pollutants generated internally or infiltrating from outdoors tend to linger, with limited passive air exchange to dilute their presence. As a result, occupants of airtight homes face heightened exposure to airborne threats, particularly fine particulate matter (PM2.5), unless active mitigation strategies are in place.

Traditional HVAC systems are generally “blind” to these acute pollution spikes. They cycle based on temperature or preset schedules, without the ability to sense or react to real-time changes in air quality. This creates a paradox: as homes become more energy efficient and comfortable, the risk of indoor pollutant accumulation increases, unless ventilation and filtration strategies evolve accordingly.

Understanding Particulate Matter and Its Health Impacts

Central to the discussion of smart filtration is particulate matter, specifically PM2.5—particles with a diameter of 2.5 microns or smaller. These microscopic pollutants can originate from both outdoor sources (such as wildfire smoke, vehicle emissions, and industrial activity) and indoor activities (like cooking or burning candles). PM2.5 is especially concerning because it penetrates deeply into the lungs, readily entering the bloodstream, and can persist in the body for months.

Exposure to elevated levels of PM2.5 is linked to cardiovascular stress and other adverse health effects, especially for sensitive populations such as children, the elderly, and those with respiratory conditions. The Environmental Protection Agency (EPA) recognizes poor air quality as a significant threat, noting that Americans spend the majority of their time indoors, further elevating the importance of effective IAQ management.

Sources and Patterns of Indoor Air Pollution

Within homes, common activities such as cooking—especially high-temperature and searing methods—can cause dramatic spikes in PM2.5. Air quality monitors reveal that such spikes occur rapidly and dissipate slowly, particularly in airtight environments. The EPA’s air quality rating system, adapted for indoor spaces, indicates that levels above 100 on its index are considered unhealthy for sensitive groups, with wildfire events often pushing levels into hazardous territory.

Filtration Fundamentals: MERV Ratings and Pressure Drop

Mitigating PM2.5 exposure relies heavily on effective air filtration. The Minimum Efficiency Reporting Value (MERV) rating, developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), is the industry standard for measuring filter performance. MERV ratings indicate a filter’s efficiency at removing particles across three size ranges: 0.3–1 micron, 1–3 microns, and 3–10 microns.

  • MERV 8: Common in residential and commercial settings. Effective for larger particles (pollen, dust) but not for PM2.5 or smaller particles that impact health most significantly.
  • MERV 11 & 13: Increasingly adopted, especially after the COVID-19 pandemic, as they capture a substantial portion of smaller particles, including some viruses and bacteria. MERV 13 is now a strong commercial standard in many states.
  • MERV 16 and HEPA: Correspond with the performance of N95 masks, capturing 95% or more of even the smallest particles.

Pressure drop (differential pressure) across the filter is a critical, often misunderstood parameter. As filters load with particulate matter, resistance increases, reducing airflow and system efficiency. California’s Title 20 regulation now requires filters to display detailed performance data, empowering consumers and professionals to balance filtration efficacy with energy consumption and system health.

It is a common misconception that higher MERV ratings always entail higher pressure drops. In reality, filter quality and design play significant roles; low-quality filters can have higher resistance irrespective of their MERV rating.

The Role of Room Purifiers vs. Whole-House Filtration

While portable room air purifiers provide a valuable second layer of defense, the central HVAC system remains the foundation of whole-house air quality management. Properly selected filters in the main system can address the entire building, whereas purifiers are most effective for specific rooms or individuals with heightened sensitivity.

Smart Filtration: Components and Operation

Smart filtration represents an advance over traditional, static filter replacement approaches. It comprises four key elements:

  1. Sensing (Eyes): Air quality monitors, preferably using laser-scattering technology, provide real-time measurement of PM2.5 and other pollutants. Responsive monitors with integration capabilities are essential for enabling dynamic system responses.
  2. Control (Brain): Smart thermostats and back-end systems interpret sensor data, running algorithms to trigger filtration only when needed. Integration with home automation platforms—and proper G-wire fan control—allows for precise, on-demand operation.
  3. Air Movement (Brawn): The HVAC system, including the air handler and ductwork, must be capable of responding to control signals and delivering adequate airflow through high-performance filters.
  4. Filtration (Shield): MERV 13 or higher filters are recommended to effectively capture PM2.5 and smaller particles. Selection should consider initial pressure drop and system compatibility.

This integrated approach allows for filtration to occur precisely when poor air quality is detected, minimizing both exposure and unnecessary energy consumption.

Performance Data: Before and After Smart Filtration

Real-world data underscores the value of smart filtration. For example, in modern, airtight homes, a single cooking event can cause elevated PM2.5 to persist for up to 15 hours if left unmanaged. With smart filtration, the same home can return to “green zone” air quality within two hours. Aggregated national data show that homes equipped with smart filtration experience, on average, a 30% reduction in PM2.5 exposure compared to those without.

It is important to note that filter loading rates can vary dramatically based on environmental events (e.g., wildfires, construction dust) and indoor behaviors. Filters can become fully clogged much faster than expected, sometimes in days rather than months, underscoring the need for monitoring rather than relying solely on visual inspections or scheduled changes.

Practical Considerations and Trade-Offs

  • Filter Life and Maintenance: Monitoring differential pressure and actual air quality is superior to fixed replacement schedules. Looks can be deceiving; filters may appear clean yet be fully clogged with fine particles or minerals.
  • Static Pressure Management: Oversized pressure drops can compromise HVAC performance. Selecting high-quality filters and monitoring system parameters ensures both air quality and system longevity.
  • Energy Consumption: Running the HVAC fan continuously is energy-intensive and often unnecessary. Smart filtration enables on-demand operation, maximizing efficiency while maintaining healthy air.
  • Integration Challenges: Not all legacy systems support advanced control (e.g., modulating fans, home automation). Retrofitting may require updates to thermostats or wiring.

Opportunities for Builders, Contractors, and Housing Professionals

Smart filtration systems offer tangible benefits beyond occupant health:

  • Reduced Callbacks: Data-driven maintenance can prevent system failures due to neglected filter changes, protecting contractors from costly warranty disputes and improving customer satisfaction.
  • Enhanced Service Offerings: Maintenance contracts or monitoring services can be enhanced with real-time data, enabling proactive support and differentiated business models.
  • Compliance and Marketability: As regulations and consumer awareness increase, homes with advanced IAQ solutions will enjoy a competitive edge.

Key Takeaways

  • Modern airtight homes require active, data-driven management of indoor air quality to protect occupant health and system performance.
  • 5 is a primary health concern; effective mitigation requires filters rated MERV 13 or higher.
  • Filter life is dynamic and should be monitored using pressure sensors and air quality monitors, not fixed schedules or visual inspection.
  • Smart filtration—combining sensing, control, air movement, and high-efficiency filters—enables on-demand operation, reducing both exposure and energy use.
  • Builders, contractors, and housing professionals benefit from reduced callbacks, enhanced service relationships, and improved market positioning.
  • Room purifiers supplement, but do not replace, the role of whole-house filtration.
  • Ongoing education and awareness are essential as standards, technologies, and expectations evolve.

Q&A: Addressing Common Industry Questions

Q: How does filter effectiveness change as filters become clogged?

A: As a filter loads with particulate matter, its efficiency at capturing smaller particles generally increases, but airflow is reduced. This means less air is being filtered overall, so the net benefit may decline depending on the rate of new particulates vs. rate of removal. New standards (such as MERV “A” ratings) now assess both loaded and unloaded filter performance, including the risk of particle “blow-through” during sudden bursts of airflow.

Q: What about volatile organic compounds (VOCs) and other pollutants besides PM2.5?

A: PM2.5 is best addressed through electrostatic and mechanical filtration. VOCs and CO2, however, are not effectively removed by standard HVAC filters and require carbon, ventilation or dilution (e.g., opening windows, using energy recovery ventilators). Low-cost VOC sensors are relative, not absolute, and should be interpreted with caution.

Q: How do pleat density and filter design affect performance?

A: More pleats generally increase surface area, reducing face velocity and increasing efficiency slightly. However, pleats packed too tightly can restrict airflow excessively. Optimal design balances surface area, media quality, and system compatibility.

Q: How do you match filter performance data to HVAC system specifications?

A: Use the system’s rated airflow (CFM) to select filters using performance charts (such as those required by Title 20). Most systems tolerate a 50% increase from initial static pressure, but specifics vary by model and installation. Always verify available headroom to avoid exceeding system limits.

Q: Can smart filtration systems help contractors and builders reduce warranty claims and improve service?

A: Possibly. Real-time data can be shared (with homeowner permission) to verify maintenance, provide reminders, and resolve disputes about equipment care. This transparency supports better relationships and more reliable system performance.

Q: Are there collaborations with the medical industry or health professionals?

A: While not a substitute for medical advice, cleaner indoor air is associated with reduced health risks. Some health professionals increasingly recommend IAQ interventions (like electrification of stoves or advanced filtration) for patients with respiratory challenges. However, building professionals should avoid making direct medical claims.

Q: What are the main integration or retrofit challenges?

A: Not all HVAC systems support advanced controls or smart thermostats out of the box. Retrofitting may require wiring upgrades (such as adding a G-wire for fan control) or selecting compatible smart home platforms. The market is rapidly evolving to facilitate integration.

Q: What are the metrics behind the AQI Color chart? Are they based on PPM or something else?
A: The EPA’s Air Quality Index (AQI) is a standardized number calculated from the amount of particulate matter (PM) in the air across various sizes. It’s not simply PPM; it’s a composite value representing air quality. More info from the EPA

Q: What rating systems exist for furnace/air filters, and how do 3M’s “MPR” numbers compare to MERV ratings?
A: There are three main standards: MERV, MPR (used by 3M), and FPR. They measure similar things—filter effectiveness at capturing particles—but use different methods and scales. You can convert between them, though the numbers don’t line up exactly. For example, a 1600 MPR is roughly comparable to MERV 13.

Fan Pressure, System Design & Title 20

Q: How do you correlate an air handler’s maximum fan pressure rating (from the data plate) with the Title 20 filter chart?
A: Title 20 provides baseline tests at various air speeds, allowing for apples-to-apples comparisons of filter efficiency. Your air handler will operate somewhere within that range, depending on its fan speed(s). Title 20 doesn’t directly indicate if your system is properly specified or facing issues; it’s more of a comparative tool.

Filter Performance Over Time

Q: How does the effectiveness of a MERV 13 (or similar) filter change as it becomes more soiled?
A: Filtration efficiency actually increases as the filter collects more particles, but this also increases the filter’s pressure drop, potentially reducing airflow. It’s a tradeoff between better filtration and reduced air movement.

Q: When you push clean air through a dirty (virus?) filter, does it still keep your air clean?
A: Yes, a dirty filter will continue to capture particles—often even more effectively as it loads up—but at the cost of higher pressure drop and reduced airflow.

Filter Types: Mini-Pleat vs. Traditional Pleat

Q: How does a mini-pleat filter compare to a traditional pleat filter?
A: Filters with mini-pleats (e.g., a 7.3mm pleat pitch vs. 25.4mm) have a much larger surface area—about three times more than traditional filters. This allows for lower pressure drop even with more restrictive, high-efficiency media like MERV 13 or above.

Q: Manufacturer claims “2.5X the pleats for higher efficiency” on mini-pleat filters. Is this accurate?
A: Increased pleat density does increase surface area and can improve efficiency and reduce pressure drop, but the benefit also depends on the filter media quality. It’s generally true, but case dependent.

Q: How are ERVs (Energy Recovery Ventilators) integrated into smart filtering schemes, especially if they’re only nominally filtered?
A: Integration can vary by system. Some resources, such as this video, explain methods. Generally, smart filtration schemes monitor air quality and dynamically control fans and filtration based on current needs.

Q: In Vermont and similar climates where ventilation runs 24/7, how does smart filtration fit in?
A: HVAC systems may run at different speeds; some run continuously at low speed, others cycle on/off. Smart filtration can ramp up fan speed in response to poor air quality events, but the approach depends on system specifics.

Q: Does smart filtering take into account CO₂, VOCs, etc., or just PM2.5?
A: Smart filtration alone may not address CO₂ or VOCs. Effective indoor air quality (IAQ) management includes monitoring for these gases and using ventilation (fresh air exchange) as needed. The key components are:

  1. Monitoring air quality,
  2. Dynamic control,
  3. Moving air where needed,
  4. Venting or filtering contaminants.

Q: If you only monitor for PM2.5, are you missing issues with CO₂ or other contaminants?
A: Potentially, yes. Many air quality monitors track PM2.5, CO₂, and VOCs. Standard HVAC filters don’t capture CO₂ or VOCs, so addressing those requires ventilation—opening windows or running outdoor air exchange systems.

Q: Is VOC filtration a missing link in IAQ?
A: Removing VOCs is challenging. While some filters include carbon to capture VOCs and odors, most lack enough carbon to be effective throughout their lifespan. Introducing outdoor air is the most common way to reduce indoor VOCs.

System Operation & User Experience

Q: How does filter effectiveness relate to air system operation? For example, running the blower 10 minutes out of every 30 without a smart thermostat?
A: Filtration only works when air flows through the filter. Even simple cycling (e.g., 10 minutes on, 20 off) can be effective at reducing particulate levels, with PM2.5 levels dropping quickly after air circulation resumes.

Q: How do electrostatic filters work compared to standard filters?
A: Electrostatic filters charge incoming particles, capturing them regardless of size. This method doesn’t rely on fine mesh to block particles.

Ductwork & Particulate Distribution

Q: Does air PM distribute evenly in a space based on height? Should return air registers be placed at specific elevations for effective filtering?
A: Generally, air movement dominates over gravity in distributing particulates, so PM does not have a noticeably uneven vertical distribution. Register height can have minor efficiency effects, but many other factors play a larger role.

Conclusion

Smart filtration represents a critical advance in the pursuit of healthy, sustainable, and efficient homes. For housing professionals, builders, and contractors, understanding and implementing these systems provides a powerful means to safeguard occupant wellbeing, protect investments, and differentiate in a competitive marketplace. As indoor air quality becomes an increasing priority, dynamic, data-driven approaches will be the cornerstone of best practices in residential building performance.

For further information on indoor air quality and smart filtration, visit the Green Home Institute’s website and access additional resources on sustainable building practices.

Key Takeaways

  • Airtight homes require active IAQ management to prevent pollutant buildup.
  • 5 is a major health risk best mitigated by high-quality, high-MERV filters.
  • Filter life varies with conditions—monitoring is superior to fixed schedules.
  • Smart filtration delivers on-demand, efficient, and effective air cleaning.
  • Data-driven maintenance benefits both occupants and industry professionals.
  • Room purifiers are supplementary; whole-home systems are foundational.
  • Proper integration and education are crucial for optimal performance.
  • Ongoing adaptation to standards and technology is essential for success.

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Guest Articles

The Complete Basement Insulation Strategy: Materials, Air Sealing and Building Science

Article by Jane Marsh – environment co

Cold, drafty basements plague homeowners across the country, driving up energy bills and creating uncomfortable living spaces. Solving this challenge requires a comprehensive strategy that combines quality materials and building science principles to ensure high-performance insulation for basements.

This guide draws on insights from Therm-All, a leader in the metal building insulation industry since 1981. The company pioneered third-party testing of after-laminated R-values and provides industry-leading energy code consultation.

Finding the Best Basement Insulation

For builders and property managers seeking the best insulation for unfinished basements, effective results depend on a complete system that combines high-quality materials with rigorous building science principles to meet current standards. Beyond selecting products, proper certification also ensures materials deliver the advertised performance throughout the building’s lifespan.

Therm-All advises that quality insulation products should carry verified certifications to protect against underperforming materials. These include NAIMA 202, UL 25-50, Home Innovation Research Labs Verification, NIA Certified Faced Insulation and environmental standards such as GREENGUARD and LEED.

Using the Right Materials

Selecting the right materials depends on moisture risk, budget and local code requirements. However, the R-value is a key factor when evaluating thermal performance. According to Energy Star, R-value measures insulation’s ability to resist heat traveling through it. The higher the R-value, the better the thermal performance. 

Rigid Foam Board

Rigid foam board insulation provides high R-value per inch, stops air leaks and resists moisture. The three main types are Expanded Polystyrene, Extruded Polystyrene and Polyisocyanurate.

The thin profiles of all three types maintain high insulation while preserving valuable basement floor space. They also simplify the installation of finish materials like drywall.

Fiberglass

Fiberglass insulation offers a lightweight and fire-resistant option that installs easily inside basement wall cavities.

However, moisture management requires careful attention. The material itself does not rot, but it can trap condensation against cold concrete walls without proper vapor barriers, potentially leading to mold growth.

Therm-All notes that fiberglass regains its thermal resistance and acoustic properties after fully drying out following water exposure. However, fiberglass wet from storm water or flood water requires removal and replacement because these water sources contain contaminants that contribute to mold and mildew growth.

Rigid Cellulose

Dense-pack cellulose insulation presents an attractive option for professionals interested in green home construction. This tightly compressed, plant-based material resists fire and pests while fitting snugly against irregular foundation walls.

Beyond its eco-friendly profile, cellulose demonstrates superior moisture management capabilities. A study from the Cold Climate Housing Research Center found that dense-pack cellulose handles moisture better than fiberglass or foam insulation. 

Ensuring Proper Air Sealing

Even the highest-performing insulation materials require proper air control measures. Air sealing closes cracks, gaps and holes in a building’s outer shell, preventing air leakages.

The Energy Star estimates property owners can save an average of 15% on heating and cooling costs by air sealing their homes and adding insulation in accessible basement rim joists.

Strict air-sealing standards are also vital to maintaining a proper thermal envelope. For example, Therm-All reports that modern energy codes establish a maximum allowable air leakage rate of 0.35 cubic feet per minute per square foot of building thermal envelope area for metal buildings. Meeting the specific threshold ensures each building maintains consistent indoor temperatures while minimizing energy waste.

Understanding Building Science and Code Compliance

Building science studies how structures function as interconnected systems, analyzing how heat, air and moisture move through building envelopes. This approach ensures insulation works safely and efficiently with other building components.

Building science principles for effective insulation rest on three foundations:

  • Durability: Keeps framing and walls dry, preventing structural decay over time.
  • Comfort: Stops cold spots and uneven room temperatures throughout the building.
  • Energy efficiency: Lowers utility bills by keeping conditioned air inside where it belongs.

Proving system performance also requires strict documentation of code compliance. A COMcheck report verifies that a building design meets the applicable U.S. Department of Energy code requirements.

Contractors typically complete this documentation, but the complexity of calculating compliance metrics often creates significant challenges. Getting assistance from companies that provide comprehensive energy code consultation, such as Therm-All, helps streamline the process.

Frequently Asked Questions

Common questions about basement insulation address key performance and installation considerations.

What is the best type of insulation for a basement wall?

The best type depends on whether the walls are finished or unfinished and the moisture levels present. Rigid foam board works well against concrete foundation walls because it resists moisture and provides a continuous air barrier. Fiberglass batts suit framed wall cavities in a finished basement.

Is it better to insulate the basement ceiling or the walls?

Insulating basement walls creates a conditioned space that remains warmer and more usable year-round. Wall insulation also protects plumbing and mechanical systems from freezing while reducing overall heating costs. Ceiling insulation makes sense for a basement that stays permanently unconditioned, separate from living areas above.

What are the common problems with basement insulation?

Moisture management poses the most significant challenge. Condensation forms when warm air comes into contact with cold foundation walls without proper vapor barriers, creating conditions for mold growth. Poor air sealing compounds this by allowing humid air to penetrate wall assemblies. Improper installation also creates performance failures when installers compress insulation or leave gaps that reduce thermal resistance.

Building a High-Performance Basement Insulation System

Effective basement insulation extends beyond material selection to encompass complete system integration. A comprehensive approach where certified materials and code-compliant design work together as a unified thermal envelope ensures optimal comfort and energy performance over time.

 

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Q&A Webinar After GHI Education Manager Uncategorized

Basics of Electric Fireplaces for Aesthetics and Health – Article

Carl Brekjern, joined us recently for our  Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or want to share it with a friend or colleague, you can now do so, as the recording and an article on the topic are available below. 

Webinar attendees learned that electric fireplaces, particularly the newer water vapor models, offer enhanced options in aesthetics, energy efficiency, and installation flexibility. Many discovered for the first time that water vapor fireplaces use mist to create realistic flame effects, are vent-free, can be installed in various locations—including retrofits of traditional fireplaces—and are available in both canister and plumbed configurations. These fireplaces often use LED lights, operate on either 120V or 240V, and can improve indoor air quality since they produce no combustion or CO emissions, making them suitable for energy-efficient and healthy homes, including Passive House designs. Participants also learned about LEED credits for forgoing traditional fireplaces and noted that, while some electric fireplaces can provide heat, many water vapor models focus on visual effect rather than heating. Overall, attendees appreciated the advancements in electric fireplace technology and aesthetics, though some wished for more in-depth technical information and expertise from the presenters.

Please help us keep these webinars and writings going by becoming a supporting GHI member or by making a donation. 

This article explores the health, energy, and design implications of fireplaces in residential construction and renovation, emphasizing the advantages of electric fireplaces. Drawing upon current green building standards, including LEED certification and the electrification movement, the article provides an in-depth look at how electric fireplaces offer a compelling solution for balancing aesthetics, health, safety, and sustainability. Designed for housing professionals, builders, contractors, and the general public, the content delivers a comprehensive overview of fireplace types, installation options, energy use, and practical retrofit guidance, offering actionable insights for both new construction and existing home upgrades.

Introduction: The Significance of Fireplaces in Green Building

The use of fireplaces in homes is deeply rooted in human culture, providing warmth, a focal point for gathering, and a connection to nature that supports mental well-being. Traditionally, the comfort and beauty afforded by wood and gas fireplaces have been accompanied by significant trade-offs, particularly in terms of air quality, occupant health, and environmental impact. As the housing industry evolves with a focus on sustainability and decarbonization, professionals are increasingly tasked with reconciling these historic comforts with modern standards for health, energy efficiency, and environmental stewardship.

Green building certification systems such as LEED for Homes, EPA Indoor Air Plus, and the electrification movement have changed the criteria by which fireplaces are assessed. These frameworks prioritize indoor air quality, carbon emissions reduction, and occupant safety, often challenging traditional methods of combustion heating. Within this context, electric fireplaces have emerged as a transformative solution, offering both the aesthetic and psychological benefits of fire without the drawbacks of combustion emissions.

Fireplaces and Green Certification Standards

In green building programs, the inclusion and design of fireplaces are regulated by prerequisites and bonus credit opportunities. The LEED for Homes standard, for example, places combustion venting under the Environmental Quality (EQ) prerequisite, which governs not only fireplaces but also furnaces and water heaters. While much of this regulation focuses on safety measures—such as backdraft prevention, combustion air supply, and sealed enclosures—the underlying goal is to eliminate or drastically reduce indoor and outdoor pollution.

LEED and similar programs encourage the replacement of natural draft units with sealed combustion or power-vented alternatives. Projects are required to undergo rigorous testing, such as the BPI or ResNet Combustion Safety Backdraft Potential Test, to ensure that backdrafting does not introduce harmful pollutants into living spaces. Failure to meet these criteria can result in forfeiture of certification, regardless of other sustainability achievements.

For professionals operating within these frameworks, understanding the compliance pathways and the rationale behind them is essential. The standards prioritize occupant health by minimizing exposure to combustion byproducts, such as carbon monoxide and particulate matter, and emphasize the need for robust ventilation and air sealing. Even when sustainable fuels like bioethanol or biomass are used, the imperative remains: combustion must not compromise indoor air quality.

The Evolution of Fireplace Technology: From Combustion to Electricity

The transition from wood- and gas-burning fireplaces to electric models represents a significant shift in both technology and philosophy. Electric fireplaces offer a number of advantages relevant to the modern home:

  • No Combustion Emissions: Electric fireplaces do not produce smoke, carbon monoxide, or other combustion pollutants, preserving indoor air quality and contributing to a healthier home environment.
  • Energy Efficiency: These units are nearly 100% efficient at the point of use, as all electricity consumed is converted into heat or light, with no losses from venting or flue systems.
  • Design Flexibility: Electric fireplaces are available in a wide range of styles, sizes, and installation modalities, making them adaptable to both new construction and retrofit scenarios.
  • Safety: With no open flame or hot surfaces, electric fireplaces present fewer fire hazards, and built-in safety features, such as overheat protection, are standard.

Green certifications increasingly recognize electric fireplaces as a preferred option. In some cases, omitting a fireplace altogether earns bonus points for simplicity and air quality. However, when the aesthetic and biophilic benefits of a fireplace are desired, electric models provide a means to achieve the best of both worlds: ambiance without adverse health or environmental impacts.

Types of Electric Fireplaces: Features and Applications

Electric fireplaces are offered in a variety of formats, each suited to different design intents and functional needs:

  1. Linear Electric Fireplaces: Modern and versatile, linear models are popular in both residential and commercial settings, including single-family homes, multi-family residences, and condos. They range in size from compact units to large, dramatic installations, and can be wall-mounted or recessed. Many feature customizable flame colors and ember beds, enhancing design flexibility.
  2. Traditional Electric Fireplaces: Designed to replicate the appearance of classic wood-burning fireplaces, these units are available as fireboxes or inserts. They are ideal for retrofitting existing mantels or replacing outdated gas or wood fireplaces, offering shallow depths for easy installation.
  3. Water Vapor Fireplaces: Using ultrasonic technology, these models create a realistic flame effect with illuminated water vapor. They are available as built-in units, linear formats, or movable cassettes, and can be installed with or without glass enclosures. While generally not intended for primary heating, they excel in realism and are particularly suited for applications where flame authenticity is paramount.
  4. Multi-Sided Fireplaces: Three-sided or bay-style electric fireplaces provide panoramic views and are often used as architectural features in open floor plans, dividing spaces while maintaining visibility and ambiance from multiple angles.
  5. Freestanding and Portable Fireplaces: These units offer maximum flexibility, requiring only a standard electrical outlet. They are popular in smaller spaces, guest rooms, or cabins, and can be easily relocated as needs change. Some models combine fireplace functionality with media consoles for added utility.

Advanced features, such as smart home integration, app-based controls, and customizable lighting, are increasingly standard across all types, catering to the expectations of today’s connected consumer.

Installation and Retrofit Considerations

One of the advantages of electric fireplaces is the simplicity of installation compared to combustion-based systems. Wall-mounted units require minimal construction—much like mounting a television—while recessed and built-in models may necessitate modest framing or drywall work. Most electric fireplaces operate on standard 120V household current, though larger models may be wired for 240V to increase heat output. This flexibility allows for both plug-and-play and hardwired configurations, with the caveat that design decisions about voltage should be made early in the project to avoid costly rewiring.

For existing homes, electric fireplace inserts are an effective means to retrofit outdated or unsafe wood and gas fireplaces. The process typically involves framing the opening, ensuring proper electrical supply, and, where appropriate, sealing off old vents and chimneys to prevent air leakage and moisture intrusion. These upgrades not only improve safety and energy efficiency but also enhance thermal comfort and the overall aesthetics of the space.

Outdoor-rated electric fireplaces further expand design possibilities, providing the ambiance of fire without the safety and maintenance concerns associated with outdoor wood or gas units. Weatherproof casings and specialized warranties ensure reliability in exposed environments, though it is important to select units specifically designed for outdoor use.

Energy Use and Efficiency: Practical Implications

A central concern for builders and homeowners is the operational cost and efficiency of electric fireplaces. Most models consume between 750 and 1500 watts—comparable to space heaters—but with the added efficiency of direct conversion of electricity to heat. Operating costs typically range from 10 to 30 cents per hour, depending on local electricity rates and whether the heating element or flame-only mode is used. In contrast, gas fireplaces often cost significantly more to operate per hour and produce emissions both inside and outside the home.

Electric fireplaces are particularly well-suited for zone heating, allowing occupants to heat occupied rooms without running a central system. This can lead to energy savings in homes where supplemental heating is desirable. The flame-only mode, powered by LED lighting, offers the visual benefits of a fire with negligible energy use—an important consideration for highly energy-efficient or passive house designs.

For all-electric homes, electric fireplaces integrate seamlessly with renewable energy systems, such as rooftop solar, further reducing their carbon footprint. While not typically designed to serve as primary heat sources, larger units can provide supplemental heat for spaces up to 1,000 square feet, making them useful in a variety of residential contexts.

Health and Safety: Protecting Occupants

Health and safety are at the forefront of green building standards, and electric fireplaces excel in these domains. Unlike combustion-based appliances, they do not release carbon monoxide, nitrogen dioxide, or fine particulates. This makes them especially suitable for households with children, elderly occupants, or individuals with respiratory sensitivities.

The front glass of electric fireplaces remains cool to the touch, reducing burn risk, and built-in overheat protection is standard. Proper installation includes maintaining clearances from furniture and flammable materials, and most manufacturers recommend avoiding extension cords and adhering to dedicated circuit requirements to mitigate electrical risks.

By eliminating the need for fuel storage, venting, or gas lines, electric fireplaces further reduce the complexity and hazards of traditional systems. These advantages contribute to healthier indoor environments and lower the risk profile for both single-family and multi-unit dwellings.

Practical Guidance for Housing Professionals and Contractors

For professionals in the housing industry, the adoption of electric fireplaces offers several strategic advantages:

  • Streamlined Compliance: Electric fireplaces simplify adherence to green building standards and local codes, often eliminating the need for complex combustion venting and air quality testing.
  • Design Versatility: The wide range of styles and installation options makes electric fireplaces adaptable to both new construction and renovation projects, supporting creative architectural solutions.
  • Cost-Effective Retrofits: Replacing old wood or gas fireplaces with electric inserts can be accomplished with minimal disruption, improving safety and energy efficiency while preserving or enhancing the room’s focal point.
  • Enhanced Occupant Satisfaction: By providing the ambiance of a traditional hearth without pollution or maintenance concerns, electric fireplaces contribute to occupant comfort and mental well-being.

Builders and contractors should advise clients to consider future electrical needs early in the design phase, particularly when planning for higher-output units or integrating with renewable energy systems. For retrofits, sealing off old chimneys and vents is recommended to prevent energy losses and moisture problems. Outdoor installations require selection of weather-rated models and attention to warranty limitations.

Key Takeaways

  • Electric fireplaces provide the visual and psychological benefits of a fire without the health, safety, or environmental drawbacks of combustion-based systems.
  • Modern green building standards strongly favor electric fireplaces for their contributions to indoor air quality and energy efficiency.
  • Installation of electric fireplaces is straightforward and flexible, accommodating both new builds and retrofits.
  • Operating costs are low, and electric models are particularly effective for zone heating and all-electric homes.
  • Safety features such as cool-touch glass, overheat protection, and the elimination of open flames make electric fireplaces suitable for a wide range of settings.
  • For retrofitting existing homes, electric inserts are an effective way to upgrade old fireplaces, improve energy performance, and reduce maintenance.
  • Coordination with electrical contractors is advised for larger units requiring 240V wiring.
  • Outdoor electric fireplaces expand design possibilities but require weather-rated models.
 
Q: Do they come with thermostats?
A: Yes.  Most models of electric fireplaces have built in thermostats so the heater will turn off once the desired temperature is reached. 
 
 
Q: What are the cassettes being mentioned?
A: The cassettes mentioned were the Dimplex Opti-Myst fireplaces.  You can have them free standing, build them into a wall or combine multiple units to create a dramatic focal point for the room.
 
 
Q: Where does the heat come from on wall mounted or built in?
A: The heater for most wall mounted and built in electric fireplaces is usually at the bottom of the unit.  Some have them at the top but it depends on the model.
 
 
Q: Is there any consideration of CO sensors to be installed with these?
A: No need for CO sensors.  Electric fireplaces do not create any carbon dioxide emissions.
 

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Q&A Webinar After

Urban and Old: Residential Energy Retrofit and Subsequent Savings Article

Marcus de la fleur, joined us recently for our  Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or want to share it with a friend or colleague, you can now do so, as the recording and an article on the topic are available below. 

What the session was about, according to our live attendees

The webinar provided attendees with practical insights into retrofitting older buildings—especially masonry structures—for improved energy efficiency and comfort. Participants learned about various insulation strategies, including the use of closed cell and open cell spray foam in combination to balance air sealing, vapor permeability, and thermal performance, as well as the importance of moisture management in every renovation step. The session highlighted real-world case studies, detailing how deep energy retrofits can succeed through careful planning, attention to detail in wall assemblies and HVAC choices, and innovative solutions like hexagonal core ERVs for better humidity and energy control. Attendees also became aware of the challenges posed by restrictive building codes, the need for knowledgeable contractors, and the financial considerations of large-scale upgrades. Importantly, the webinar reinforced that user behavior and ongoing maintenance ultimately determine the effectiveness of even the most advanced systems, emphasizing that the key to long-term efficiency lies in both technical choices and how occupants interact with their buildings.

Please help us keep these webinars and writings going by becoming a supporting GHI member or by making a donation. 

Article Based on Webinar*

 

This article explores the comprehensive process of retrofitting a historic masonry residential building for high energy performance and sustainability. Centered on a case study from Chicago’s West Side, it details the technical, strategic, and practical challenges of transforming a turn-of-the-century, multi-unit property into a near net-zero, healthy, and resilient home. The discussion covers building envelope upgrades, mechanical system optimization, moisture management, ventilation, renewable energy integration, and lessons for professionals and the general public aiming to decarbonize older housing stock. The article is intended for housing professionals, builders, contractors, and anyone interested in deep energy retrofits, balancing technical rigor with accessible explanations.

Retrofitting Urban Masonry Housing for a Sustainable Future: Lessons from a Deep Energy Retrofit

The transformation of legacy urban housing into energy-efficient, healthy, and sustainable residences is a critical strategy for addressing both the housing crisis and the urgent need to decarbonize the built environment. Older masonry buildings, which are abundant in many American cities, pose unique challenges and opportunities in this endeavor. Through a detailed case study of a deep energy retrofit of a 1902 masonry two-flat in Chicago, this article illustrates best practices, technical considerations, and real-world lessons for housing professionals, builders, contractors, and engaged citizens.

The Opportunity and the Challenge of Existing Housing Stock

Preserving and upgrading existing housing is vital for reducing emissions, supporting urban connectivity, and meeting rising housing needs. Existing buildings often suffer from excessive energy use, poor air quality, and deferred maintenance—issues that contribute to both environmental and social challenges. At the same time, their embodied carbon and location advantages (such as walkability) make them prime candidates for sustainable transformation.

Yet, the path to high performance in these structures is far from straightforward. Masonry walls, outdated windows, leaky envelopes, and legacy mechanical systems present complex interrelated problems. The case study building, a 4,500-square-foot, three-unit property, exemplifies these challenges but also demonstrates the potential for remarkable improvement through careful planning and execution.

Energy Baseline and the Priority of Envelope Improvements

A rigorous approach begins with establishing a baseline for energy performance. A blower door test revealed that the subject building leaked air at a rate equivalent to a 22-inch by 22-inch open hole in the wall—typical for its era but unacceptable for efficiency and comfort. Energy modeling underscored that space conditioning (heating and cooling) was the dominant energy load, directing focus to the building envelope as the most impactful area for intervention.

Envelope improvements encompassed insulation and air sealing of the basement floor, foundation walls, above-grade exterior walls, windows, doors, attic, and roof. Special emphasis was placed on moisture management, recognizing that improper insulation strategies can lead to condensation, mold, and structural damage. The solution required assemblies that preserved the drying potential of the walls in both directions.

Wall and Roof Assemblies: Technical Solutions for a Historic Masonry Building

The wall assembly selected for the project consisted of a “flash and batt” strategy: a one-inch continuous closed-cell foam layer (carefully chosen for vapor retarder—not barrier—properties), two inches of open-cell foam, and 3.5 inches of rockwool batts within the interior framing. This assembly provided robust insulation (R28-R40, depending on location) and targeted airtightness of 3 air changes per hour at 50 Pascals.

The roof was upgraded with two layers of polyisocyanurate boards above the deck and three layers of rockwool batts below, all air-sealed with drywall and vapor-retarding latex paint. This approach delivered an R-value of 60 while minimizing the risk of cold deck condensation and preserving the roof’s drying potential. The roof assembly also included details such as a dimple mat at the parapet to facilitate vapor venting.

These solutions, developed in 2009, would likely be complemented by even more advanced products today, such as smart membranes and alternative insulation materials. The key takeaway is the necessity of project-specific strategies, tailored to the building’s physical characteristics and performance goals.

Air Tightness and Windows: The Details That Matter

Air sealing was an exercise in diligence, requiring the building to be gutted to its masonry shell. All thermal bridges and penetrations were addressed, with deferred maintenance issues uncovered and resolved. The result: air exchange rates dropped dramatically from 13.9 to 0.62 air changes per hour at 50 Pascals—far exceeding the initial target and fundamentally improving comfort.

Window selection and installation are critical in high-performance retrofits. The project specified triple-glazed, airtight windows (0.2 cfm/sf or less), with a mix of fixed casement and awning styles to minimize air leakage and maximize manual ventilation options where needed. Installation was performed with meticulous air sealing, recognizing that poor installation can undermine even the best window products.

Mechanical Systems: From Gas to Efficient Electrification

The building’s mechanical transformation followed the envelope upgrades. Initially, a small, modulating gas boiler provided hydronic heating with low-temperature radiators and radiant floors. By 2016, the system transitioned to ductless cold-climate mini-split heat pumps, sized by updated energy modeling to avoid undersizing (causing discomfort) or oversizing (causing short cycling and poor dehumidification).

Mini-splits were located centrally in each unit to balance temperature distribution, with supplemental fans improving air mixing. The case study found that while temperature differentials remained minor (2-4°F), the key benefit was the mini-splits’ sufficient dehumidification during summer and continued operation during sub-zero winter conditions, albeit with reduced efficiency at extreme lows. Importantly, the mini-splits’ right-sizing allowed for predominant operation in “dry mode” rather than full cooling, maximizing comfort and minimizing energy use.

Despite these advances, the existing gas boiler remained as a backup and for domestic hot water production, due to code limitations and product availability. The ultimate electrification goal includes replacing the boiler with an air-to-water heat pump, further reducing fossil fuel dependency and enabling all-electric operation powered by on-site solar.

Ventilation and Indoor Air Quality: Essential for Healthy, Tight Homes

With high levels of air tightness, mechanical ventilation becomes non-negotiable for occupant health. The project implemented energy recovery ventilators (ERVs) with high efficiency, strategically located to supply fresh air to living spaces and exhaust from bathrooms. The ERVs’ balanced ventilation not only maintained indoor air quality but also minimized energy penalties by recovering both sensible and latent heat.

Special care was taken with duct sealing (using mastic and gasketed connections) and layout, avoiding returns in kitchens to prevent grease buildup in the ERV core. Range hoods were specified with low cfm to prevent depressurization, with code-compliant makeup air solutions considered for higher-capacity exhausts.

Performance Outcomes: Energy Use, Economics, and Comfort

After improvements, annual kilowatt-hour consumption per apartment was approximately half the Illinois average—including most winter heating. The installation of an 8.58 kW photovoltaic array further reduced net energy costs, bringing the building close to net zero in years when heat pumps provided the majority of heating.

Economic analysis revealed the heat pumps outperformed natural gas heating when paired with on-site solar, with annual savings exceeding $200 per apartment. Without solar, the economics fluctuated with utility rates but remained competitive. The payback period for the solar array was projected to reach positive returns within 7-8 years, after which the system would provide decades of ongoing savings.

Comfort improved dramatically, with stable indoor temperatures, controlled humidity, and fresh air—intangible benefits that reinforce the value of high-performance retrofits.

Moisture Management, Durability, and Lessons Learned

Moisture management emerged as a central theme throughout the retrofit. Wall and roof assemblies were designed to maintain bidirectional drying, with materials selected for appropriate vapor permeability. Low-tech monitoring—visual inspection of masonry and joints—proved sufficient, with no evidence of moisture problems over more than a decade of operation. Passive radon mitigation was integrated during basement upgrades as a precaution.

The project’s experience highlighted the importance of contractor selection and supervision. Green building competencies remain rare among contractors; success often depends on close collaboration, oversight, and mutual learning.

User Behavior, Controls, and Occupant Education

No retrofit is complete without addressing occupant behavior. The best technology can be undermined by habits formed in drafty, inefficient buildings. Education for tenants included utility cost transparency, training on ventilation systems, and guidance on optimal thermostat and system use. Building management monitored humidity via smart thermostats, intervening as needed to prevent mold risk.

In multi-unit or rental contexts, the variability of occupant choices can affect net-zero goals and energy performance. The experience suggests that user education, ongoing engagement, and smart controls are essential complements to physical upgrades.

Site and Water Management: Holistic Sustainability

Sustainability extended beyond the building envelope. The project incorporated low-flow fixtures, roughed-in graywater systems (pending code approval), and stormwater strategies such as rain gardens to mitigate combined sewer overflow risks—a significant urban challenge in Chicago. Site interventions were designed for future adaptability and integrated with the building’s resilience goals.

Looking Forward: Future-Proofing and Continuous Improvement

The case study underscores the value of strategic planning and future-proofing. Decisions made in 2009, such as hydronic system design and utility room layout, allowed for later integration of new technologies. Today’s broader array of insulation materials, air sealing products, and smart membranes would offer even more options for performance and durability.

Continuous improvement is part of the sustainable building journey. Plans for further electrification, equipment upgrades, and site enhancements remain underway, reflecting the evolving landscape of building science and technology.

Conclusion

Retrofitting historic masonry housing for energy performance, health, and sustainability is both a technical and human challenge. Success depends on a holistic approach—envelope upgrades, mechanical optimization, ventilation, moisture management, user education, and renewable integration—tailored to each building’s unique context. The lessons from this Chicago project provide a roadmap for housing professionals, builders, contractors, and the general public committed to transforming the existing housing stock into resilient, low-carbon, and livable homes.

For further information and resources, Green Home Institute remains committed to empowering professionals and residents to make informed, sustainable choices in building and renovation.

Key Takeaways

  • Deep energy retrofits of masonry housing can achieve dramatic improvements in energy performance, comfort, and health while preserving embodied carbon and urban infrastructure.
  • Building envelope improvements—insulation, air sealing, high-performance windows—are the foundation of sustainable retrofits and must be tailored to each project’s unique challenges.
  • Moisture management and vapor permeability are critical considerations in all envelope assemblies, especially for historic masonry structures.
  • Mechanical systems, particularly right-sized heat pumps and energy recovery ventilation, are essential for decarbonization and indoor air quality in tight homes.
  • Renewable energy, such as photovoltaics, delivers substantial operating cost savings and supports net-zero goals when paired with envelope and system upgrades.
  • Contractor expertise and hands-on quality control are necessary to ensure proper installation and system performance.
  • Occupant behavior and education significantly influence real-world energy savings and comfort; smart controls and ongoing engagement are vital.
  • Site and water management, including stormwater mitigation and future-proofing for water reuse, contribute to holistic sustainability.
  • Retrofitting is an ongoing process; strategies should prioritize adaptability and incorporate emerging technologies and practices.
  • Strategic planning, data-driven decision-making, and collaboration across disciplines are key to successful, scalable energy retrofits.

Additional Questions and Answers not in the webinar 

Q: Are the Fujitsu heat pumps still working ten years later?
A: Yes, they still work great.


Q: Marcus, would you share the total project cost and whether you received any grants?
A: $180,000 general deep energy retrofit budget, $15,000 back porch rebuild, $17,000 re-roofing, $15,000 cornice and parapet repair, $30,000 solar roof array, $14,000 for three ductless minisplits. Rebates: $1,500 in Energy Star rebates, $1,500 insulation rebate, $1,450 heat pump rebate, 30% Federal tax credit on solar array installation, $9,300 state rebate on solar array installation.

Q: How many attendees were there today? Nice presentation.
A: 200.

Q: How many and what type of water heaters did you use? Could a hybrid water heater be installed in the garden level to reduce humidity?
A: We have one indirect fired water heater for the whole building (120 gallon insulated storage tank).

Q: Do you recommend a smaller, typical air-forced HVAC system with better air sealing/exterior insulation so that the user learning curve is reduced or eliminated?
A: I personally have a deep-seated dislike for forced air systems, and as such it was never on my radar or an option for us. As such, I don’t really have any recommendations I could pass on.

Q: Given everything you’ve learned and experienced, what would you do differently given today’s updated technologies and evolving building science for masonry retrofits like yours (new insulation types, heat pump advances, airsealing products, etc.)?
A: I probably would sequence some of the improvements and tasks differently (more effectively). I would go with a different, more reliable check valve (backwater valve) system from the outset. Rather than applying insulation uniformly across the interior walls, I would increase the insulation in those rooms where I had the space to do so.

Q: Pipe insulation from big box stores has been seen to be short-lived and still externally hot to the touch. Did you use a better grade of pipe insulation?
A: Yes, I used professional grade elastomeric pipe insulation and fittings.

Q: Can you talk a little more about why you incorporated the layer of open cell spray foam? Understood that minimizing the closed cell thickness avoids it becoming a vapor barrier, but open cell spray foam doesn’t really have a much better R value than mineral wool batts. Why not just add more mineral wool instead of open cell?
A: I wanted the potential heating season dew point to be in the spray foam and not the rockwool insulation to minimize condensation and bulk water issues.

Q: Window saddle heat pumps seem to be a coming technology that is much easier and therefore less expensive to install. They are not possible to fit with crank windows at this point. How would you weigh the heat retention advantages of crank windows versus the convenience and expense advantages of saddle heat pumps?
A: I personally would take a systems approach here, and not just look at the potential lower cost of a saddle heat pump. If just looking at cost, a saddle heat pump may be a short-term fix, but not necessarily cost-effective in the long run.

Q: How did you manage the behavioral learning curve with your tenants?
A: It’s an ongoing process. What I noticed is that demonstrating the potential cost savings will more reliably lead to behavior changes—particularly in this economy.
 
*Content created by a human speaker, transcribed by Zoom, and arranged by an AI LLM
 
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GHI Education Manager

My experience with wildfire smoke: Impact on indoor air quality and solar power

Recently, in mid-July 2026, Canadian wildfire smoke entered Michigan, resulting in the worst air quality I can recall in my lifetime.  For two days, we sat in the hazardous range listed within the EPA AQI rating. Everything was foggy, like a normal heavy-fog day, but the air outside tasted like metal and smelled like a distant wood fire, but not the pleasant kind. In addition, we had just come off a heatwave that week, and some of the days were fairly hot during the smoke event.
 

I had no interest in doing this or writing this, as I do not take pleasure in it. Still, I decided to take advantage of the bad situation and to run indoor air quality experiments to see how outdoor air was affecting my indoor air quality and solar power output.

 
My first action Wednesday night when the smoke started to descend into Michigan was to shut down my Energy Recovery Ventilator (ERV), think lungs for your house, a system that brings in fresh air and exhausts stale air. The reason I did this was the hazardous level of smoke coming in; I was worried that even my robust MERV 13 filter on the ERV and MERV 16 filter would not filter out the additional pollution a wildfire brings beyond particulate matter like Pm2.5 and PM10.
 
By shutting down my ERV, I was making a conscious trade-off: I knew I may increase
Airthings monitor in hallway near thermostat showing CO2 spikes
household CO2, certainly, and maybe to a minor extent indoor VOCs and humidity, but the trade-off was not letting the nasty wildfire pollution into my home.  In addition, I set my heat pump filter (same as your furnace/AC filter) to high recirculation mode because it is a MERV 16 filter designed to filter out wildfire smoke that gets pulled into the house, even with the ERV off.
 
Now, while I do not have an outdoor air quality monitor to know exactly the air quality directly at my house, I do have several indoor air quality monitors, so I have tracked my air quality before, during, and after this event.
 
One of the first things I noticed on the first major smoke day was that we used our local ventilation systems, such as a range hood to vent while we were cooking or a bath fan to vent while we were using the bathroom or taking showers.
 
The first spike on the left was from turning on the range hood to cook breakfast; the 2nd spike was from lunch made in the oven with the range hood on again; and the 3rd and 4th spikes were from running the bath fan during showers.
 
Spikes in PM2.5 from local ventilation on hazardous level (500 AQI) smoke day show on Awair air quality monitor inside
 
So basically, what’s concerning here is that one turns on their ventilation systems to remove pollution, but during extreme wildfire events, you’re actually bringing more pollution into the house. My home is about 978 CFM and/or four (4) air changes per hour, which is not the tightest home, but that’s what our current code is here in the State of Michigan. Other states and other green building programs are usually around that level as well.  But that’s enough leakage to worry about if you bring on an exhaust-only fan like a constantly running bath fan, which the vast majority of our homes, even newly built ones, and multifamily buildings are using as we speak. It’ll draw in that polluted air through the cracks and crevices in the home, and keep it in there. You will see some more examples of this below.
 
Now, one thing I didn’t get to experiment with was whether turning off my high-
efficiency filtration system in my heat pump would have caused my particulate pollution numbers to go up, since my home isn’t super airtight. This was because it was very hot out, and so I had to keep my heat pump cooling my house, which meant the filter was running as it should be, so the only way to experiment with that would’ve been to turn off my heat pump and suffer through heat just to see how my house handles smoke without any mechanical systems running. Certainly, if we have a hazardous wildfire event in one of the swing seasons, when I don’t need to be heating or cooling, I could test that out and update.
 
Speaking of a wish list of things to test, as the hazardous smoke wound down, someone on LinkedIn told me they decided to switch their ERV system to positive pressure to help keep the smoke from entering the home by pushing the air out the natural leaks in all homes and then using their MERV 13 to filter the incoming air. I wish I had tested this more during the hazardous smoke, but I did switch over to this by moving the exhaust dial to 70 CFM and maintaining 100 CFM on the intake during the next few days when we spent most of the time in the EPA IQA unhealthy and very unhealthy range, and it seemed at least effective there.  
 
Now, that being said, our Green realtor friend Wayne, who works in the Chicagoland area, shared an update of his house using his air quality monitor on LinkedIn during the event. He told me he wasn’t home at the time, and his energy recovery ventilation

 system was running and drawing in the outdoor air through a MERV 7 filter and only being filtered through the standard low MERV heat pump conditioning system, so you can see from his post that his house quickly became polluted until he shut the system down the numbers went down from the red to yellow and so they were still elevated in higher threshold above what people should be consistently exposed to. He also shared that his house is pretty tight, around 1 air change per hour, showing even in tighter homes some pollution was coming in and it was not being cleaned by a MERV 7 filter system.
 
Now how does a more advanced Passive House fare? Dale Hulst, who recently built MINet0-1, got to experiment with this as he currently has his home listed on the market but has it monitored.

 “The big smoke event was a great test of the house. It performed well, but not as well as I’d hoped given my MERV16  final filter on the Energy Recovery Ventilator. I decided to upgrade the recirculation plenum filter (the system with three duct fans that I added late in the game). I upgraded from MERV 11 to MERV 13, toward the end of the smoke event, on July 20 in the afternoon, and thought I saw improvement, but it was hard to know for sure as the outdoor air was significantly cleaner by that time.  We’re likely to see some bad 300+ AQI days again, which will be

 a better test.” – Dale Hulst.

Dale also shared with me that this particular Energy Recovery Ventilator has a MERV 13 intake filter ahead of the MERV16 final filter which also includes carbon for removing VOCs from the incoming fresh air.

 
 
“My goal is to show the new buyers / owners they can safely run the ERV in a wildfire event. With the fresh filters and upgraded MERV13 in the recirc system, I’d like to think I could run it. Some of the PM2.5 in the house may have been from the little bit of infiltration that gets into the house through the doors, etc.  (0.03 CFM/FT2 at 50 pascals per final blower door test). If the ERV is taking out everything intentionally being brought in, my hope is the recirc filter will take out whatever is unintentionally leaking in.”- Dale Hulst.
 
 
 
So just going on beyond a couple anecdotal examples here with myself, Wayne and Dale, where I grow really concerned is when I look back over the last 15 years I’ve been providing consultations to help people at where I have just helped people achieve our building code in Michigan, which is four air changes per hour (4 ACH) and typically includes running a negative pressure bath fan to meet the ventilation standards, which are typically referred to ASHRAE 62.2.
 
Beyond that even the Green Building Certification programs we help consultant on such as LEED or Green Communities are fairly similar at the lower levels where typically people are just at a bare minimum meeting somewhere between two and four air changes per hour in their home or multifamily units, then having a bath fan run to meet the basic ventilation standards such as ASHRAE 62.2 2010 or maybe 2016 and then putting in a MERV8 filter in the HVAC system.
 
In all these cases and all these homes that are otherwise designated to meet a new building code or even a green standard, one can infer that people went into their houses thinking they were protecting themselves from the wildfire but heavy smoke at these levels are shown here above with their bath fan that is running and would’ve been otherwise used to keep their air healthy in their house was instead pulling in the wildfire smoke, and the MERV 8 in their HVAC system filter wasn’t enough to filter it but only spread it around. Maybe some of these people were savvy enough to notice and shut down their bath fans, install HEPA filters, or build a DIY Corsi–Rosenthal Box fan at some point, but that likely is not the case for most people who are not thinking about these things.
 
My main point is that, unfortunately, our current codes and Green Building standards are not protecting us against this new threat, which was probably unforeseen here in the Midwest and Northeast.
 
I would argue this is an opportunity to reflect on and review our building codes. Look at our Green building programs and significantly increase their requirements while providing the resources available for home renovations in new construction to achieve these outcomes.
 
The good news is that, even if, let’s say, wildfire smoke rarely came again or ever came again, the benefits of making our homes wildfire smoke-resistant would extend beyond just keeping smoke out to include improved home health, comfort, and energy cost savings.
 
So what do we need to do?
  1. Airseal, airseal and then airseal again, ideally to Passive House levels
  2. Boost HVAC filtration to MERV 13-16 (but be warned if you do!)
  3. Get Smart; systems need to know air quality and respond to smoke events
  4. Change policy/programs

First and most important, we need to air-seal our homes and reduce leaks, ideally aiming for Passive House standards to the best of our abilities. This can be done easily on new construction, but once the home is built, it gets harder and harder depending on its condition, unless there’s a gut renovation.  Beyond keeping smoke out during extreme events, we also have humidity control, which reduces winter dryness and summer/swing-season mold/allergy issues, reduces energy loss, and could lead to improved comfort, especially during extreme heat or cold. Also, in many areas with air leaks, pests can enter the home, and water can get in those areas as well, so targeting air leakage has multiple benefits beyond just smoke.

Next, we need to boost the filtration capacity of our ventilation, heating, and cooling systems. The problem with doing this, though, is that the heavier the filtration is, the more drag it puts on the system’s efficiency due to something called static pressure. With new construction, this can be easily addressed through Manual D, where you properly design the ductwork and include a 4- to 5-inch filter with MERV 16 as part of the total system design and proper install. Then the HVAC is properly commissioned to verify that the installation works and the system is performing. Some HVAC systems even self-commission and can report issues during operations.

For existing homes, this becomes a lot more complicated because in many cases you are stuck with the ductwork you have, as it can be very expensive to get to tearing out drywall, tearing out walls, and tearing out and replacing ductwork; rarely do any of the energy efficiency programs or weatherization pay for this work but getting a good HVAC contractor assess the existing system for performance is still important and improvements can be paid or funded through some programs. You would have someone review the ductwork during a GreenHome Inspection, maybe do duct blaster testing or pressure pan testing to see how leaky it is, and check to see if ducts are panned in the joists. Then, check the length and size of the ductwork, and have the HVAC contractor or assessor complete a static pressure test on the existing system to see what its current pressure is. From there, a plan can be put together that is specific to each property to determine if it’s possible to update to at least a MERV 13 filter, which is what is needed to start filtering out wildfire smoke, or even a MERV 16 without dragging down the static pressure and reducing the life and efficiency of the system. Each home is going to be on a case-by-case basis, depending on the situation, budget, and the homeowner’s or building owner’s desires. If a home is using ductless air source heatpumps (aka mini-splits)  to heat and cool, or radiant, you might have to try to do the filtration through the ventilation system instead.
Now for ventilation systems, these are usually a detriment to health and extreme wildfire smoke, but the first thing we need to do is make sure they have thick filters in them and are also designed appropriately with good static pressure without major bends or kinks in the ductwork and lots of 90° or sharper turns. I haven’t seen too many ventilation systems with MERV 16 on them other than Dale’s noted above, but I know many like what I have; the Panasonic Intellibalance one has at least a 13 on it, which helps. But more than this, we need smart ventilation and demand-controlled systems that can automatically: sense bad air, shut down, and recirculate, as most people aren’t thinking about these kinds of things on a daily basis and want to rely on the system to ensure their safety before it is too late. This would mean that the ventilation system is communicating with an outdoor air quality monitor on the house, in the area, or, if necessary, with the general EPA outdoor air quality data. Then the system would also monitor indoor air quality and either shut down the intake based on how bad it gets outside and what’s being sent inside, or maybe even throttle it back. Hence, it was a balance between some ventilation and reducing higher levels of particulates in the house. But as I said, if you’re relying on your ventilation system to filter the air because your HVAC is older and can’t have the updated filter, or you’re using mini-splits or radiant heating and cooling, then you’ll want to rely on your ventilation system to shut down, but still provide filtration for the home, and I’ve never seen any system do that short of a Build Equinox CERV unit which has the ability to detect the outdoor water wildfire smoke and do just that shut down from being a ventilation system to just a filter system which then we’ll filter the air in the home only for any of the wildfire smoke that migrate in through the cracks and crevices.  
 

To be fair, this can all be expensive, so in the short term, what we highly recommend is a low-cost air quality monitor that can review particulates, and then a DIY filter fan that you can build a couple and set up in a room during emergencies.

But moving forward, I think it’s imperative that our codes and green building programs change, as well as our incentive structures, to help fund these kinds of advanced upgrades during Home retrofits, or especially during new construction, where it’s a lot easier to take care of.

The good news, too, is more and more people may be willing to pay for these upgrades; a recent Redfin report shows 36% of buyers value a clean air home over other luxuries. 

 

What about solar power?

So I promised to talk about solar power. Certainly less of a worry because the majority of people don’t have solar power, but we all breathe; if you do, or you’re considering it, wildfire smoke is going to be a detriment to solar power output just the same.

Solar before smoke on a typical July day

Now, thankfully, I had one really nice full sunny day right before the wildfire smoke event, and then during one of the most hazardous days, the weather told me, at least according to the weather, I couldn’t see because of all the smoke that it was truly a full sunny day without any clouds. But otherwise, most of the smoky days we had also had clouds, so that skewed some of the data, but if you look at the sunny day right before the event and the sunny day during the event here, you’ll see all in all we had a 17 kW decrease in solar

 percent again from extremely rare hazardous smoke output or otherwise a 27%

change.

This similair % drop is confirmed by Dale Hulst of MINet0, who also confirmed his solar data with me; you can see on average his home peaks at 70 kW and on the smokiest yet sunniest day (same as mine) he dropped to 50 kW, so 28%, pretty close and his system is a bit bigger and all south facing so of course the bigger they are, the harder they fall or state larger systems will see larger % drops.

So overall, unfortunately, as more wildfire smoke is forecasted to occur. we will also lose energy output with solar power, ironically, as solar is meant to reduce carbon emissions and help prevent climate change, which worsens wildfire smoke in forest fires. The good news is, despite the smoke output, I still was able to stay off grid most of the day and most of the peak energy usage time, and the other good news is the smoke will depress the heat from the sun, which is another thing that diminishes solar panels: extra heat.

If you want to see more details about my home, the monitors, systems I use, etc as well as a CEU tour of my house, go to https://greenhomeinstitute.org/greenstar_homes/little-residence-pearl-platinum-aiming-for-greenstar-zero-carbon/

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The Resilient Home: Building Materials and Best Practices for Reduced Mold Risk

The Resilient Home: Building Materials and Best Practices for Reduced Mold Risk

By: Grace Waters, Senior Editor, Environment Co

Mold prevention starts long before a building is occupied. It begins with choosing the right materials, managing moisture effectively and following construction practices that keep water out. While mold spores are naturally present in the air, they only grow when moisture is available. As such, designing with moisture control in mind is the key to creating healthy, durable and resilient buildings.

1. Moisture Control as the Foundation of Mold Prevention

The most effective mold prevention strategy is to control moisture before it accumulates within building assemblies. Water can come from rain, plumbing leaks, high indoor humidity or condensation, so moisture management should be a priority during design and construction.

 

Building envelopes should prioritize continuous water-resistive barriers, properly integrated flashing, effective drainage planes and airtight construction. These components work together to direct water away from vulnerable assemblies while minimizing uncontrolled air leaks that can transport moisture into wall cavities.

 

Proper site grading also helps with moisture management. Directing surface water away from foundations, incorporating appropriate drainage systems and preventing standing water around the building perimeter reduces the likelihood of long-term moisture infiltration.

2. Selecting Mold-Resistant Building Materials

Mold can begin growing within just 24 to 48 hours while producing allergens and irritants that impact health. While no material is entirely “mold-proof,” many modern construction products are designed to minimize moisture absorption and discourage microbial colonization.

Fiberglass-Faced Gypsum Board

Fiberglass-faced gypsum board has become an increasingly preferred alternative to traditional paper-faced drywall in moisture-prone spaces. Because fiberglass facers contain little organic material, they provide fewer nutrients for mold growth while maintaining similar structural performance.

Cement Board

Cement board remains a reliable substrate for bathrooms, kitchens, laundry rooms and other high-moisture environments. Unlike gypsum-based products, cementitious boards resist deterioration during repeated wetting cycles. Alternatively, fiber-reinforced concrete and other renewable or recycled substrates can be used to reduce emissions by up to 40% by 2050.

Moisture-Resistant Insulation

Engineered insulation materials also contribute to mold resistance. Closed-cell spray polyurethane foam, rigid foam insulation and mineral wool provide low moisture absorption while helping maintain consistent interior surface temperatures. By reducing thermal bridging and minimizing the potential for condensation, these materials strengthen the building’s overall resistance to mold.

Durable Exterior Cladding

Exterior cladding systems should be selected for both durability and moisture management. Masonry, metal panels and properly detailed rainscreen assemblies promote drainage and drying while reducing prolonged moisture exposure behind exterior finishes.

Mold-Resistant Flooring

Concrete, ceramic tile, natural stone and moisture-resistant vinyl products generally outperform carpeting and untreated wood in areas susceptible to elevated humidity or occasional water exposure.

3. Design for Drying

Keeping moisture out is important, but buildings should also be designed to dry out if water gets in. Instead of trapping moisture inside walls, modern building designs allow it to escape while preventing excessive buildup.

 

Features like ventilated rainscreen systems create an air gap behind exterior cladding, helping water drain away and allowing walls to dry naturally. Proper roof and attic ventilation also helps reduce condensation, protects roofing materials and lowers the risk of mold developing over time.

4. Control Indoor Humidity

Good ventilation is essential for preventing mold, even in well-built homes. Whole-home ventilation systems, like ERVs, reduce moisture compared to supply-only ventilation, and ventilating dehumidifiers bring in fresh air while helping control indoor moisture.

Bathrooms, kitchens and laundry rooms should also have exhaust fans that vent directly outside to remove excess humidity. Keeping indoor humidity between 30% and 50% helps prevent mold growth while improving comfort and protecting building materials.

5. Reducing Future Mold Risk

Using mold-resistant materials is only part of the solution. Proper installation and quality construction are just as important for preventing moisture problems.

Keep Materials Dry During Construction

Building materials should be protected from rain and allowed to dry before walls and ceilings are closed up. Using moisture meters to check lumber and sheathing can help ensure they are dry enough before insulation and finishes are installed.

Seal Common Leak Points

Areas around windows, doors, roofs, plumbing and foundations are especially vulnerable to water intrusion. Proper flashing, sealants and waterproofing help keep moisture from getting trapped inside the building.

For example, proper chimney flashing and waterproofing prevent rain from entering surrounding roof assemblies, reducing the risk of moisture damage and mold growth. Ensuring proper waterproofing helps protect the structure around a chimney from moisture damage while reducing the risk of toxic gas exposure and undesirable odors. Consider adding in heatpumps and sealed combustion appliances like water heaters and furnaces to then allow the removal of the chimney entirely during the roofing project. 

Inspect Before Closing Walls

Regular inspections during construction can catch moisture issues or installation errors before they are hidden behind finished walls. Addressing problems early is far less costly than repairing mold damage after the building is complete.

Building for Long-Term Performance

Creating a mold-resistant home requires more than selecting specialized products. It needs an integrated design philosophy that considers moisture control throughout every stage of planning, construction and material specification. Effective drainage, continuous air barriers, humidity management, proper ventilation and durable moisture-resistant materials all contribute to a building capable of maintaining healthy indoor conditions for decades.

As such, prioritizing these principles transforms mold prevention from a reactive maintenance concern into a proactive design strategy. The result is a resilient home that supports structural durability, occupant well-being and sustainable performance throughout its entire life cycle.

 

 

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The Hidden Impact of AC Maintenance on Home Embodied Carbon

Most conversations about a home’s carbon footprint focus on operational energy, such as the electricity an air conditioner draws while it runs. Embodied carbon typically receives far less attention. 

 

Not understanding the emissions associated with manufacturing, transporting, installing and replacing an AC system can create great blind spots. When energy and material consumption are taken into account, the embodied carbon of AC equipment can rival the amount of carbon it releases over years of actual operation.

Why AC Equipment Carries So Much Embodied Carbon

An AC system is an assembly of many components, such as compressors, condenser coils, refrigerant lines, fans and ductwork. These components carry their own upstream emissions from mining and fabrication, as well as material costs for manufacturing. Refrigerant production adds another layer, since many refrigerants used in such systems have a high global warming potential if they leak. 

 

None of this shows up on a utility bill, which is part of why it’s so easy to overlook. A homeowner comparing two AC units based solely on their energy efficiency ratings is only seeing half the environmental picture.

How Maintenance and Replacement Add Up

Replacing components has its own embodied-carbon cost each time, since every replacement part was manufactured somewhere before it arrives at a home. A system patched together with frequent part replacements over its lifespan can end up carrying more cumulative embodied carbon than one properly sized and maintained from the start. This is simply because more manufactured components are cycled through. 

 

Full replacement carries an even larger embodied carbon hit, and it’s also where timing plays a notable role. An aging unit approaching the end of its service life is often better replaced than repeatedly patched. This is because continued part-by-part repairs on a failing system can consume more material and cause more disruption than a single, well-planned replacement with a properly sized unit. 

 

Refrigerant handling during maintenance deserves particular attention. Servicing an AC system involves opening refrigerant lines, and improperly handled service work can release refrigerant into the atmosphere — a direct emissions event separate from the embodied carbon of manufacturing. Proper recovery and recharging prevent refrigerant from being vented during a service call. This matters because refrigerant leaks create climate impact regardless of how efficiently the AC unit runs day to day.

Designing Homes That Need Less From Their AC

The most effective way to reduce an AC system’s lifetime embodied carbon is to decrease how hard it has to work in the first place. Much of this comes down to the building itself rather than the equipment. 

 

Poor insulation is one of the most common culprits behind an underperforming AC system. A home that isn’t properly insulated allows unwanted heat gain regardless of how well the equipment itself is running, which is one of several factors, including excess indoor humidity or an aging system, that reduce an AC system’s cooling power.

 

Improving insulation, sealing air leaks, and adding shade through window placement, overhangs or landscaping all reduce the cooling load a home places on its AC system. These solutions reduce operational energy use and the frequency of maintenance and premature replacement.

 

Passive design strategies extend this further. For example, using cross-ventilation to move heat out naturally reduces reliance on mechanical cooling. Homeowners can also consider orienting a home to limit direct afternoon sun exposure. While none of these strategies eliminates the need for an AC system in most climates, each one reduces the runtime and strain on the installed equipment, extending its usable life and delaying the embodied-carbon cost of eventual replacement.

What to Look for When Equipment Is Unavoidable

An AC system is still necessary in many climates, but a few equipment choices can meaningfully reduce lifetime carbon impact. Right-sizing a unit to a home’s actual cooling load reduces wear from constant short-cycling and extends the equipment’s realistic lifespan. 

 

Furthermore, systems that use lower-global-warming-potential refrigerants reduce the impact of future leaks during servicing. Equipment with a high efficiency rating and a strong track record of parts availability also makes long-term maintenance easier, since it keeps a unit in good working order longer rather than pushing it toward premature replacement. 

 

Adopting a direct approach to reducing emissions is typically more beneficial to the environment than carbon offsets, which often take an indirect approach to tackling core emissions issues. 

Rethinking What Efficiency Means

An AC system’s environmental footprint extends far beyond its operational use. Every replacement part and service call involving refrigerant carries its own embodied carbon, and that carbon adds up over a home’s lifetime in ways that operational efficiency ratings don’t capture. By treating equipment longevity and building design as part of the sustainability equation, homeowners can have a much more complete picture of what it actually costs to keep their living space cool. 

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Cost Savings When Going All Electric for GHI Members

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