The ENERGY STAR Program has released a new technical bulletin on microwaves, and you might be thinking, does ENERGY STAR certify microwaves? Well, no. The efficiency of any microwave typically stays mostly the same. It’s already the most efficient form of cooking, even compared to induction. (Is it the healthiest? We are not here to discuss that.)
So why is ENERGY STAR releasing updates on microwaves?
It’s because microwaves are often installed directly above stoves in place of what ideally should be a vent. Vents are important because stoves release a lot of pollution that needs to be immediately vented. The best way to do this is to have a range hood directly above the stove, tested and proven to pull 100 – 400 cfm of air. The second best way to do this is to have a whole home ventilation system, such as an energy recovery ventilator (ERV), that always provides five air changes per hour to the kitchen space.
Now, back to the microwave.
Microwaves are often installed above the range hood for convenience, counter space management, and cost. Still, unfortunately, these devices have proven not as effective as a range hood that only vents.
ENERGY STAR has released guidelines on installing these devices to ensure they vent properly.
These guidelines include first determining whether the microwave can even vent, as many do not. Next, confirm the microwave was third-party tested by a reputable organization to ensure proper flow. Look at the microwave static pressure and CFM; if you are trying to hit a residential green building standard, a building code, and/or just want to ensure proper flow, you must oversize the microwave vent with higher static pressure and CFM. Because these units often do not move air as well as a hood-only unit and the bends, kinks, and ductwork added to a unit further reduce its ability to move air, oversizing will help ensure the ideal 100 cfm is reached.
ENERGY STAR’s guidance gives advice and visuals on proper installation; it then goes on to provide guidance on how GreenHome Inspectors / Raters can properly test these units. We have seen that sometimes they need to bring a piece of cardboard to the job site to cover the microwave fully as the vent is much too large to cover with their testing device, compared to a traditional hood.
Our Find a Pro page has GreenHome Inspectors, Raters, and Certified HVAC professionals who can help ensure this is done correctly and help to increase the sustainability and performance of your home or project in other ways as well.
It is a good idea to ensure the HVAC contract includes provisions for the company to correct installation errors.
Improving your range hood ventilation may also be worth Inflation Reduction Act tax credits or rebates; consult your tax advisor and local state agency for guidance.
Finally, in addition to good air quality, another aspect of human health is accessibility. Microwaves above the stove are inaccessible to people with mobility or height challenges. They are not as accessible as putting the microwave on the counter. So, to improve health, air quality, and accessibility, keep the microwave on the counter and install a range hood instead.
