MassCEC’s whole-home air-source heat pump pilot launched in May 2019, and last month MassCEC announced that we are extending the pilot through June 25, 2021. This month MassCEC’s Board of Directors approved a follow-up iteration to this pilot. We’re calling the new pilot Decarbonization Pathways, and it will move beyond whole-home heat pumps to focus on complete whole-home decarbonization (i.e., entirely removing fossil fuels from existing homes while making them more efficient). Decarbonization Pathways will test a third-party decarbonization assessment with a diverse cohort of around 100 homes. We’ll help those households create customized transition plans and begin to implement changes. To learn more about the proposal for Decarbonization Pathways and offer feedback please take our survey by December 18, 2020.
In the meantime, an update on this pilot: so far we have awarded a total of $278,750 to 89 projects out of an available budget of $500,000. Of those 89 projects, 57 are existing building retrofits, 7 are gut rehab projects, and 25 are new construction. See our previous monthly blog updates for more information about the pilot.
Heat Pumps and New Construction
I’d like to focus my November update on heat pumps for new construction homes. Heat pumps are a strong choice for new construction homes before you even consider climate impacts because they offer heating and cooling in one system without having to connect a development to a gas line.
Last month, the Rocky Mountain Institute (RMI) published an analysis on the economic and carbon emissions impact of all-electric new construction, single-family homes versus natural gas in seven cities across the country. They found that an all-electric home has a lower net present cost over the first fifteen years of the home’s life than a natural gas home in all seven cities, as well as significant greenhouse gas emissions reductions.
In Boston specifically, RMI found that greenhouse gas emissions were 69% lower in the all-electric home and upfront costs were cheaper. Even with the cheap natural gas prices we’ve seen recently and relatively expensive electricity prices in our region, the two homes had nearly equivalent annual energy bills in RMI’s modeling, with a 3% higher annual utility cost for the all-electric home. While heat pumps aren’t ubiquitous in new construction yet, this matches some of the anecdotal stories that I’m hearing of developers switching over to heat pumps based on simplicity and cost.
If you’re interested in further resources on heat pumps in new construction, last year MassCEC offered a training on clean energy for new construction (available for free online) that includes several modules on heat pumps.
Project of the Month: Northampton Net Zero New Construction
I’ve begun to profile one completed whole-home project every month to give readers a sense of what it’s like to live with a whole-home heat pump system. You can see past profiles from August, September, and October.
This month I want to feature John Saveson’s new construction home in Northampton, MA. Saveson is passionate about efficiency, so, working with his builder, he designed an extremely efficient home with high levels of insulation in the roof, walls, and basement slab, plus triple pane windows and heat recovery ventilation. Based on his interest in efficiency and his plans to build a net zero home, heat pumps were a natural fit for this homeowner, and he says that he would have selected them even if there weren’t a moratorium on new natural gas connections in Northampton.
The home’s conditioned area is 3,100 square feet (including an unfinished basement) with a peak heat load of 23,103 btu/hr. Saveson selected three Fujitsu AOU9RLS3 single-head units to heat and cool the home. Each of those units has a capacity of 15,000 btu/hr at 5°F, for a combined peak capacity of 45,000 btu/hr at 5°F. However, each unit can also modulate down to 3,100 btu/hr meaning that they can match the load of the home even on mild days. There is one head in the unfinished basement, one in the open plan first floor, and one on the second floor landing. The total installed cost of the three heat pumps was $13,750, including a ten percent markup for Saveson’s general contractor.
Saveson moved into the home in September 2019, so he has lived with the heat pumps for over a year. Overall, he finds that they do their job without being noticeable and that they’re very easy to live with. The units are quiet, and he hasn’t noticed any noise or vibrations from the outdoor units that are mounted on the wall of his home.
Last winter, Savenson’s household ran the first-floor heat pump to heat the entire house. This meant that their bedrooms were slightly cooler, but that matched his family’s preference. During hot periods of the summer, they ran the upstairs unit for cooling, and even though overall this unit cooled the house well, the bedrooms stayed slightly warmer, especially with the doors closed, which was less desirable. Saveson selected single-head heat pumps because they have the best efficiency and range of operations. He still feels strongly that a single head is the best fit for the main space in the home based on efficiency, but in retrospect he says that he would consider some kind of distribution to the upstairs bedrooms for cooling comfort. Saveson says that his family does not use the unit in the basement much (they had not needed it for heat as of our conversation on November 20th), but having the conditioning in the basement ensures that it stays comfortable even with a heat pump water heater that cools the basement and gives them more flexibility in how they use the space. For example, during the pandemic Saveson has been using the basement as his office.
After putting in a 10kW solar array in April, the home has been producing more energy than it consumes, although Saveson recently bought an electric vehicle which will use some of that excess energy.
These photographs show the three Fujitsu AOU9RLS3 outdoor units mounted on the side of Saveson’s home (left), plus an example of one of the indoor heads (right).