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Transitioning to Carbon Free Homes


Henry MacLean is an Architect in Milton. He has served as a past board member of Sustainable Milton and chair of the Milton Alternate Energy Committee.


Almost 14 months ago, the Inflation Reduction Act was signed which together with the bipartisan Infrastructure Law, is now working its way its way into new green tax rebates and incentives, projected to save up to $38 billion to American families by 2030, and develop 1.5 million new jobs in American communities. Of course this new funding is welcome news after this 2023 summer, bringing us the longest and hottest heat wave in recorded history. These combined plans are focused on doubling clean renewable electricity to reach 80% by 2030, while helping us break our dependance on coal, oil and gas.


Our Mass Clean Energy Center ( MA CEC) has been helping educate and lead homeowners in the specific areas of focus listed below on graphic from the “Clean Energy Lives Here”, and provides this helpful list of incentives, benefits and savings. Of course this is all happening as the country is finally coming to embrace a zero carbon emission policy to avoid irreversible climate catastrophe, keeping global temperatures from exceeding 2.7 degrees F.


A building’s efficiency is measured in BTU’s, per square foot, per year. Also known as a building’s energy utilization rate (EUI), the equivalent to MPG (miles per gallon) for cars, or now MPkW(miles per kilowatt) for electric vehicles( EV’s), it is measured per thousand, or kBTU / SF/ YR. Here in Milton with the majority of single family homes, we know that the average home uses roughly 70 kBTU /sf per year. Energy intensive homes range up to 200 while high performance homes get down to about 25, and Passive House standards get down below an EUI of 15 (kBTU/SF/YR).


Over the last 25 years, I’ve been working on dropping our Crosby Colonial’s EUI 72%, while increasing the conditioned area 56%. The increase was achieved in phases and included renovating the original unused breezeway and basement to new living spaces, while keeping the original footprint. The 1947 jalousie breezeway became a breakfast room off the remodeled kitchen, with new windows and glass doors opening to a new 300 SF deck and patio area below.


With our yard sloping down seven feet to the southwest, we cut new windows into the original basement walls , creating new well-insulated day-lit spaces for family room, office, laundry, bath, and shop below the garage. The home’s landscaping also became more fully linked to the house, managed by my wife Didi Emmons, an avid gardener, food writer and chef. She has done wonders to expand and restore the garden space, reduce lawn area and invasive species, while we’ve transitioned to electric powered machinery and a green minded lawn care company.


The 1947 exterior walls received blown in insulation, while the attic and garage were super insulated. In 2018 we added 5.4 KW of PV panels whose 8 yr payback (or 14% ROI) will start giving us free electrons in 2026. In 2021, we added a new five-zone air-to-air heat pump system, replacing a 2-zone gas fired hydronic loop. This system includes an energy recovery ventilation system (ERV) that pre-heats incoming fresh air with outgoing stale air. This critical element provides the make up air needed once our house was tested for air tightness with a blower door test , part of the CEC rebate program. After 1 year of operation, we tracked a 43% decrease in

energy use and a 65% reduction in carbon emissions.


With this data ( & new and deferred costs added up), the system is on track to give us a 7% ROI while adding great comfort and real estate value. Our solar system, maxed out for our location, provides up to 50% of our annual electric use, with the remaining 50% coming from 100% Green electricity though Milton’s CEA program, which powers our EV’s as well.


In 2022, we completed the retrofit of all the remaining original single pane units to triple pane glazing, and with additional insulation over and under the bonus room over our garage, dropped our EUI another 15% to 25. We are now now jumping into the final steps in getting to a carbon by replacing our gas water heater and dryer with heat pump units, and swapping out our gas stove with an induction electric stove. These changes will also save another 50% of the combined energy our gas units now use.

A good place to start, even with an interested 8th or 9th grader at home, is running your own carbon footprint with the well tested UC Berkeley Cool Carbon Calculator and then taking full advantage of the great CEC programs. As Secretary General Guterras stated in the fall of 2022, “the climate emergency is a race we are losing, but it is a race we can win.”


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