Author: Brett Little

Brett Little, GHI Education Manager, recently led a virtual tour of his house in a Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or share it with a friend or colleague, you can now do so, as the recording is available below. In addition, Max answered some of the remaining Q&A below, and your question may have additional follow-up below.  

Participants learned a wide range of insights from the webinar, with many highlighting the importance of sequencing improvements—particularly that solar panels should be the last upgrade after reducing loads and improving efficiency. People gained knowledge about heat pump water heaters (including the need for flushing/maintenance), the value of green home inspections, radon mitigation and monitoring, energy and water tracking systems, differences between ERV/HRV and dehumidification, financial incentives and rebates, and how proper equipment sizing and duct choices affect comfort and efficiency. They also appreciated seeing real-life case studies of retrofits, the evolution of “good idea” systems, and lessons learned from Brett’s own homes. Many found the monitoring tools for air quality, radon, noise, and water use to be eye-opening. At the same time, questions remain about specific costs of converting from gas to electric, choosing and integrating indoor air monitoring devices, understanding pros/cons of different dryers and ventilation systems, affordability of geothermal, and how to integrate automation tools like electronic water valves with sensors. Overall, attendees valued both the technical details and the broader lesson that creating a green home is an ongoing journey requiring planning, patience, and careful decision-making.

Check out more details on Brett’s home and technologies here

Questions and Answers

Q. What about thermal solar to charge the water heater tanks?

A. This was not even considered because no one installs these systems, they can leak and because it is cheaper and better to add more PV and power a heat pump water heater.

Q. Does the tax credit for geothermal systems sunset this year on January 1? That’s what I have heard

A. Yes, HOMES 25D, which is a credit for solar and ground source heat pumps, sunsets Dec 31, 2025. Consult your Tax advisor on further information.

Q. Retrospectively, If that extreme polar vortex lasted longer, or was in northern Plains (Canada), would you add a back-up system to the heat pump system for resilience ?

A. I am concerned about power outages in the winter, it would be difficult to function in extreme cold, no power, and no sun.

Q. Do you have any new insights on monitoring or enhancing a wildfire filter system, if you started today ?

A. I am not sure other than a smart ERV that shuts down when PM2.5 gets too high, check out the Build Equinox CERV2. Thankfully, my climate risk factor for fire is very low here (for now).

Q. If you see a home changed from baseboard heat and the HVAC, which has ducts in the ceiling, but the ones running to the return air vents are just interior walls…is there a problem? Think a house built in the 50s…

A. Yes, very concerning, leaks, humidity issues, lack of delivery, the list goes on. Not an issue with my house.

Q. Do you use lose microwave clocks when switching to battery in outage?

A. No.

Q. Have you calculated your 2024 utility costs using the 2016 rates (to have a fair comparison to the prediction, i.e., eliminate the utility cost inflation?)

A. Not yet, but I am looking into it. It is hard because in 2016, there was also no time of use pricing, and I did not track back then, when I used energy, or at least I never downloaded that data to know to track it.

Q., Do you have ceiling fans in your home? Or would you consider using ceiling fans to help distribute air and reduce air stratification in rooms?

A. I do, I no longer use them, I used to. I think it is a great idea but there other impacts of ceiling fans on mental health that people may need to consider, it is likely a rare issue but one to consider.

Q. What is a “professional” water heater tank flush? I turn off the heater twice a year and open the drain for five minutes. No sign of CaCO3 in flush water.

A. Having a plumber or HVAC come and flush it out if you are not comfortable doing it

Q. Does your air handling system handle MERV 16? Usually, MERV 11 or 12 is the limit?

A. Well, it works, but I need to get a static pressure test done. We never did one in COVID during install.

We recently hosted Sandra Lupien and Anthony Harvey on our Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or share it with a friend or colleague, you can now do so, as the recording is available below. In addition, they answered some of the remaining Q&A below, and your question may have additional follow-up below.  

The survey results reveal that attendees learned a great deal about the structural, environmental, and regulatory aspects of mass timber (MT) construction. Many were surprised to learn how tall MT buildings can be—some exceeding eight stories—and that there are already numerous MT projects across the U.S., including over 65 in Michigan. Participants gained new insights into mass timber’s fire resistance ratings (e.g., char calculations and ASTM standards), its favorable strength-to-weight ratio, and how it compares in durability and speed of construction to steel or concrete. A recurring theme was MT’s carbon-sequestering benefits and biophilic impacts on occupant mood, alongside cost-saving potential due to quicker assembly and pre-fabrication. Several responses highlighted unfamiliar MT types like dowel- and nail-laminated timber and clarified common misconceptions (e.g., heavy timber vs. engineered MT). Participants appreciated learning about 2021 IBC code updates, applications in multifamily/commercial settings, and the importance of early site planning and penetrations. Remaining questions or interests include exploring existing MT projects (especially regionally), understanding lifecycle comparisons with other materials, grant opportunities, and deeper dives into code compliance, cost estimating, and design integration for MEP systems and egress cores.

### Questions and Answers

 

1. **Question:** What kind of VOCs or off-gasses are produced and linger from CLT?  

   **Answer:** Reach out to Woodworks for assistance. The adhesives used are fossil-fuel-based polyurethanes, which cause some off-gassing, mainly in factories. In buildings, it’s minimal. There is ongoing research into bioadhesives that could enhance sustainability.

 

2. **Question:** Can dead wood from beetle kill or wildfires be used as mass timber?  

   **Answer:** Yes, sometimes. It depends on how long the wood has been dead or the extent of fire damage.

 

3. **Question:** How is Michigan building out its mass timber supply chain infrastructure?  

   **Answer:** Several entities are exploring expanding or starting operations for mass timber in Michigan. Commitments may emerge in the next 12-18 months.

 

4. **Question:** What are some of the largest barriers to the adoption of mass timber at scale?  

   **Answer:** The biggest barrier is that estimators often don’t know how to accurately estimate mass timber projects, leading to higher estimates than necessary.

 

5. **Question:** What is the cost difference between traditional mass timber framing vs engineered mass timber?  

   **Answer:** This is a complicated topic. There may be a cost premium for materials, but construction efficiencies can make mass timber cost-competitive. Estimators need to collaborate with suppliers for accurate costing.

 

6. **Question:** What is the rate of high fire resistance for mass timber?  

   **Answer:** Covered in 2nd hr. Reach out to Woodworks for assistance.

 

7. **Question:** How amenable are CLT floors to being modified for plumbing, HVAC, and electrical?  

   **Answer:** MEP considerations are a large topic. Reach out to Woodworks for assistance.

 

8. **Question:** Are the panels a tongue and groove connection to each other?  

   **Answer:** Only T&G decking. CLT has some side lap connection options.

 

9. **Question:** What about noise transmission?  

   **Answer:** Use built-up assembly to improve acoustics.

 

10. **Question:** How well do mass timber systems take to field modifications/renovations?  

    **Answer:** It would be handled just like any other structural system. Reach out to Woodworks for assistance.

 

11. **Question:** Do the panels need fire caulking between joints?  

    **Answer:** This depends. Reach out to Woodworks for assistance.

 

12. **Question:** What wall construction is typical exterior of the mass timber?  

    **Answer:** Exterior wall assemblies are very common, similar to steel and concrete projects with mass timber as the structural backup.

 

13. **Question:** Is there a way that radiant floor PEX can be integrated into mass timber floor?  

    **Answer:** Yes.

We recently hosted Max Reichlin on our Weekly Wednesday Free CEU webinar Series.

If you missed this session, want to rewatch it, or share it with a friend or colleague, you can now do so, as the recording is available below. In addition, Max answered some of the remaining Q&A below, and your question may have additional follow-up below.  

You can access the web based tool here

You can access the excel tool discussed here

Webinar Survey Revelaed: Participants learned a great deal from the session, particularly about using real-world utility data—rather than theoretical models—to perform energy-based load calculations for HVAC systems. Many found the Thermentor tool to be a valuable and accessible resource for simplifying this process, with repeated mentions of its usefulness, free availability, and ability to replace or supplement Manual J calculations. Key takeaways included understanding how to calculate heating loads from energy bills, how R-squared values help gauge data quality in regression analysis, and the value of top-down versus bottom-up methods. Attendees also appreciated learning where to find helpful tools like Thermentor and DegreeDays.net, and how actual energy usage enables more accurate, comfort-focused decisions about HVAC sizing and upgrades. Remaining questions and uncertainties centered on how to address variable heat loads, potential limitations of the method when estimating multiple variables, and whether this approach can be reliably used for broader energy modeling beyond heating loads. Overall, the training sparked curiosity and empowered attendees to explore these tools further.

### Questions and Answers

1. **Using previous electric bills to calculate and size PV systems?**  

   **Answer:** Energy-based loads are especially helpful for getting your head around the home’s existing energy use. Projecting new scenarios is a little more complex and depends on what’s being replaced. For predicting solar PV sizing, Clean Power Research has another product called WattPlan (www.wattplan.com) which applies much of the same data, but is focused on PV, EV.

 

2. **For the BTU calculation, don’t you need to subtract out the therms used for water heating and cooking?**  

   **Answer:** Yes. For an HDD type analysis like in the spreadsheet, you can assume that the summer constant load represents the water heating/cooking loads, which are largely constant throughout the year. Thermentor does the math differently, but the net result is the same – we assume that there are constant annual loads and remove those from the temperature dependent loads.

 

3. **What efficiency would you use for heat pumps? Assume a COP 2-3 but where is the best place to find that?**  

   **Answer:** For back of the napkin calculations, I usually use a COP of 3. For more granular estimates, you can use the HSPF/SEER of the units. It’s not perfect because the COP varies with temperature, but it will give you something to work with. Another good option is to use performance data from AHRI / NEEP if you have specific equipment in mind.

 

4. **Do you find that the swing months have lower efficiency because of more on/off losses?**  

   **Answer:** We’ve not observed that effect in our datasets, but I would expect it to appear most in single stage air conditioners/heat pumps and less in simple heating systems like gas furnaces.

 

5. **What is R squared?**  

   **Answer:** R² is a statistical measure of the correlation between two datasets. If R² is 1, the datasets are basically identical. If R² is 0, there’s no relationship between them. It’s not a perfect metric, but it helps to indicate if the data is likely valid.

 

6. **I’ve used this method before and it generates load estimates 2-3 tons less than other methods, like Manual J. Comments on these differences?**  

   **Answer:** We’ve seen similar results. Bottom-up methods are conservative, which is why ACCA recommends not overadjusting estimates. Our dataset from NEEA shows that these methods often overestimate heat loss.

 

7. **Is it wise to also consider refinements for anticipated change in HDD based on climate model predictions or increased cold-season thermostat settings as occupants age?**  

   **Answer:** Yes, the heating rate found through energy data can be extrapolated for anticipated changes in user heating needs. Adjustments can be made for expected changes in thermostat setpoints or design temperatures.

 

8. **What impact do you believe air leakage has on load calculations? Is it important to have a firm measurement of air leakage before proceeding?**  

   **Answer:** Air leakage affects both sensible and latent loads and depends on variables like wind speed and humidity. If a home is using excessive energy or reporting drafts, evaluating the envelope is crucial for comfort.

 

9. **Only see 17 states to choose from in the app. Will other states be added?**  

   **Answer:** We are adding almost all the missing states except Alaska this week.

 

10. **On heating type, it says Electric Furnace as a choice. Does that include heat pumps?**  

    **Answer:** No, we don’t currently support existing heat pumps, but we are looking into adding it soon.

 

11. **Does Central Air include heat pumps when that is added?**  

    **Answer:** Kind of? Air conditioners and heat pumps have similar cooling functions, but heating loads will be incorrect if using a heat pump primarily for heat. Caution is advised.

 

12. **What data was the R-value slide scale on the last slide associated with?**  

    **Answer:** The R-value in Thermentor reflects the overall thermal resistance of the home, including insulation and leaks. It’s based on the model’s physics and may exceed 10 in highly efficient homes.

 

13. **Would like to see a heat pump option on existing heat/cool, which would be helpful with replacing an existing heat pump.**  

    **Answer:** Thanks for the feedback! We’ll try to get existing heat pumps into the queue.

 

14. **Can you use a gas furnace if they have a boiler?**  

    **Answer:** Yes, that should be fine as long as you have an idea of the existing efficiency. If the boiler burns oil or propane, wait for support for delivered fuels.

 

15. **Will AI take over electrical load management in the future?**  

    **Answer:** It seems demand-side management is growing. I expect to see automated demand control for homeowners, but the specifics of underlying models are uncertain.

 

16. **Spreadsheet?**  

    **Answer:** Should be included in this follow-up.

 

17. **Demo did not change BTUH when Average vs Well Insulated was used. Why not?**  

    **Answer:** You probably didn’t click the “Calculate Loads” button again. You need to hit “Calculate” to see new results.

 

18. **Would the future of the Excel doc include using CDD similarly for cooling loads?**  

    **Answer:** Yes, CDD would have a similar approach, although AC’s/heat pumps are generally more efficient, making their energy signat harder to discern.

 

19. **Does Thermentor have a web API?**  

    **Answer:** Not yet, but we are looking into developing one and would love to hear your use case.

 

20. **When using Thermentor in coastal regions, which temp data should be used in the model?**  

    **Answer:** Thermentor currently uses dry bulb temperature. We plan to add improvements that assess solar loads, humidity, and wind speed biases.

 

21. **If doing new Geo Thermal HP, is it best to do separate Heat and Cool sub-systems due to humidity issues?**  

    **Answer:** Yes, it may be wise in any installation with significant heating and humidity loads during summer.

 

22. **Energy Collectives… Expect an Energy Synergy revolution?**  

    **Answer:** Ha. While change will be gradual, data is guiding our understanding of homes as interconnected systems rather than isolated boxes.

We recently hosted Lindsey Love on our Regen Building on our Weekly Wednesday Free CEU webinar Series.

 

If you missed this session, want to rewatch it, or share it with a friend or colleague, you can now do so, as the recording is available below. In addition, Lindsey answered some of the remaining Q&A below, and your question may have additional follow-up below.  

 

The webinar survey responses reveal a high level of engagement and learning about natural insulation materials, particularly straw, hemp, wool, cellulose, reed, and cork. Many participants were surprised by the fire resistance, mold resistance, and growing affordability of these materials. Several learned about specific products like straw structural insulated panels (S-SIPs), cellulose batts, bound reed boards, and hemp fiber boards. Concepts like vapor permeability, moisture management, and cavity vs. exterior insulation were clarified for many. There was also increased awareness of the geographic variability in product availability and the evolving supply chain. Questions still remain around moisture modeling for specific climates, fire resistance standards, code enforcement, best practices for installation (like running electrical through straw), and the long-term durability of natural materials. Some attendees expressed interest in reviewing more on vapor permeable systems and wished for better regional access and training on these alternatives.

 

Q&A Response

### Q2: How do some of the “in cavity” applications perform with self-drying due to vapor drive?  

**A2:** Natural insulations can work well in cavity if they are surrounded by or encapsulated with vapor-open materials. Moisture will migrate towards an equal state, so if you allow it to escape to a dryer environment, it will. Plastic vapor barriers and foam insulations are not vapor open, which increases the risk of moisture problems. Using “smart membranes,” vapor-open weather resistant barriers, vapor-open finishes, shear panels (plywood or OSB), and/or exterior insulations are safer and lead to more durable assemblies.

 

### Q3: Can you elaborate more on the rainscreen cavity acting as a chimney, specifically regarding fire mitigation rather than ‘what is a rainscreen’?  

**A3:** While we don’t often see rainscreens with very wide gaps, it’s good to be aware that if they are over 1/2″ wide and open at both the top and bottom, they may have the potential to act as a chimney under the right conditions.

 

### Q4: How do you handle moisture management in a strawbale wall? Is it less critical if you’re not trying to keep the interior face of sheathing warm?  

**A4:** It’s important to keep materials inside a wall dry, regardless of whether it’s straw, fiberglass, or foam insulation. The strategies for straw bale walls are not different from any other. Straw bales make a great plaster substrate, and using natural, vapor-open plasters (lime or clay) is effective. If sheathing is necessary, use plywood instead of oriented strand board, along with a vapor-open weather resistant barrier and rainscreen with your finish of choice. Good drainage and flashing design on the exterior are especially crucial when using plasters.

 

### Q5: It’s great to see foam products reducing their GWP, but they’re still flammable, right?  

**A5:** Yes, foam products always require chemical fire retardants and remain quite flammable, even with these additives.

 

### Q6: Are there recyclable options for tapes/membranes?  

**A6:** In my community, plastic recycling options are limited to bottles only. While some areas have recycling opportunities for flexible plastics like bags, building membranes are not yet recyclable. Tapes are typically a single-use material due to their very sticky adhesives, but membranes can be salvaged and reused.

 

### Q7: What is the best thermal performance (R-value) of some of these natural materials?  

**A7:** Fiberboard insulations have a slightly higher R-value per inch, while batts and boards range from 3.3 to 4 per inch. Straw bales and chopped straw have slightly lower R-values, and when combined with a binder, such as “light straw clay” or “hemp+lime,” the R-value decreases, creating a different application.

 

### Q8: What do you think about using Aerobarrier for air sealing?  

**A8:** Although it’s not available in my market yet, my colleagues in Colorado have used it and liked it. It seems to be a great option, using a relatively small amount of petrochemicals to effectively target air sealing. Air sealing is easiest and most effective early during construction, but Aerobarrier can be utilized at multiple phases because it is fairly invisible and can serve as a backup plan if needed.

 

### Q9: We are building in coastal Florida with AAC block, so we do not have additional exterior wall insulation. How can we achieve a sealed attic without spray foam?  

**A9:** I need more information about what you mean by a “sealed attic.”

 

### Q10: Can Structural Insulated Straw Panels be used horizontally or angled as part of a roof assembly?  

**A10:** Yes, companies like Savick in Canada offer roof and floor panels made with chopped straw. New Frameworks and their SEED partners provide similar options but use cellulose instead of packed or chopped straw. Some European companies also produce horizontal panels, and “Strawtegi” panels with chopped straw can be used in this manner. A roof would be treated like an unvented “hot roof” and should be moisture protected, meaning you need to air seal at the interior, avoid penetrating the air seal with systems, and use vapor-open sheathing and roofing membranes.

 

### Q11: How do electricians and plumbers deal with the panels?  

**A11:** It depends on the panel. Some panels are best served by having an interior cavity for services, while others may have different requirements.