ANN ARBOR, MI — Ann Arbor science writer Ken Garber recalls he was a University of Michigan student taking physics classes in 1977 when UM physics professor Marc Ross proposed transitioning buildings from gas furnaces to heat pumps.
“He wrote a report to Congress on this,” Garber said. “At that time, climate change was not yet a thing. Ross’ argument was based on thermodynamic efficiency.”
Under the laws of thermodynamics, heat can be transferred even from the cold outside to inside a building, which is the principle behind heat pumps, Garber said, noting they’re much more efficient than burning gas. And when powered with renewable energy, they’re a way to heat and cool buildings without generating planet-warming emissions.
Ken Garber speaks in support of reducing carbon emissions to address climate change at the Ann Arbor City Council meeting on Nov. 4, 2019.Ryan Stanton | The Ann Arbor News
Heat pumps are not theoretical. They’ve long existed — just not yet widely adopted in American society as a replacement for gas, partly due to upfront financial costs.
They’re now a key strategy of Ann Arbor’s A2Zero plan to become carbon-neutral by 2030 to fight climate change.
As the city considers a ban on gas for new buildings and aims to roll out more financial incentives for residents and businesses to ditch gas and transition to all-electric buildings with renewable energy, some trade union and building industry representatives argue the city’s plans are too ambitious.
“I think it is too quick. We need to be careful,” said Bloomfield Hills-based developer Howard Frehsee, who has two apartment buildings under construction in downtown Ann Arbor that will use gas: a 19-story high-rise behind the Michigan Theater and a five-story companion building next to it.
There may be reasonable alternatives in the future, but banning gas in new construction now would have repercussions, Frehsee said.
“It’s going to increase the energy costs of any project and it’s going to make it hard to have affordable housing,” he said, arguing it also could make it more costly to develop in Ann Arbor and have a negative impact on the city’s growth.
The construction site of a 19-story high-rise and five-story companion building behind the Michigan Theater off Washington Street in downtown Ann Arbor on Dec. 29, 2022.Ryan Stanton | The Ann Arbor News
City officials are listening and wrestling with those concerns, but climate activists and others who support the city’s sustainability goals still think it’s doable.
‘We have a climate emergency’
Garber spoke out before City Council recently, attempting to dispel the myth that all-electric buildings aren’t realistic. Some already exist in Ann Arbor and more are being built by developers who are prioritizing sustainability.
The 450-unit Arbour on Main apartment complex about to break ground on South Main Street is planned to be fully electric with rooftop solar, and so is the Veridian at County Farm neighborhood now underway off Platt Road.
Others in the works include a 250-unit apartment complex on State Street, a 79-unit apartment building on Maple Road and a quadplex on Division Street.
Another local builder has been building all-electric, solar-powered homes with air-source heat pumps on Fulmer Court.
There are multiple types of heat pumps to heat and cool buildings without burning gas, including air-source heat pumps, which have a unit mounted outside much like an air conditioner, and ground-source heat pumps, also known as geothermal energy, tapping into the earth’s relatively constant ground temperature via underground pipes, with either deep wells or coils buried four to six feet deep.
An air-source heat pump outside the home of Wayne Appleyard of Sunstructures Architects. The outdoor unit plus two indoor air handlers and one branch box, along with duct work for the system inside the home, cost about $25,000, he said, explaining it was "a bit more expensive" than a simpler system.Wayne Appleyard
With an electric motor, heat pumps compress refrigerant gas into liquid, raising the temperature, and can produce two to four times more heat energy than electrical energy expended, Garber said, noting that’s an energy efficiency rate of 200% to 400%.
“Compare that to the highest-efficiency gas furnaces at 97% — they can never reach 100%,” he said.
That’s why Ross told Congress in the 1970s there should be a conversion to heat pumps, Garber said.
“Even back then, burning gas was a thermodynamically stupid way to heat buildings,” he said. “Fast forward 45 years, we have a climate emergency.”
A 97% burn efficiency for gas furnaces has been cited as a positive by a trade union that has pushed back on the gas ban, saying coal or gas power plants that may have to generate more electricity for all-electric buildings have only a 50-60% burn efficiency and that could create more emissions.
Garber argues using heat pumps more than cancels out that difference in combustion efficiency.
“When you’re converting electrical energy to heat energy at 400% efficiency, you have lower emissions,” he said. “Heat pumps — even using dirty DTE power — are twice as clean as gas-heated buildings.”
‘There’s always heat’
John Mirsky shows off the heat pump for his geothermal heating and cooling system and his dual water heater system, which taps into the output of the heat pump, at his home in Ann Arbor on Wednesday, Jan. 11, 2023.Jacob Hamilton
Ann Arbor Energy Commission Chair John Mirsky, who has a background in mechanical engineering and spent many years working for Bosch, installed a geothermal heat pump system several years ago to heat and cool his nearly 2,400-square-foot, midcentury-modern home, where he also has rooftop solar panels and other electric appliances.
He set up the house to be extremely comfortable and to heat it economically, he said, noting that included doing work on the building envelope to improve efficiency, replacing old windows and adding insulation.
A heat pump is not only a replacement for a gas furnace — it also replaces an air conditioner, since it works in reverse, Mirsky noted. In air-conditioning mode, it pumps heat outside, and in heat mode it brings heat inside.
“There’s always heat that can be extracted,” he said.
His house is now all-electric except for a gas fireplace and a propane grill, he said.
“It is absolutely doable that we get off of gas,” Mirsky said, noting cold-climate heat pumps work even in subzero temperatures.
John Mirsky shows off the inverters for his solar panels and two separate electric meters, one for his geothermal system, at his home in Ann Arbor on Wednesday, Jan. 11, 2023. The extra meter is the only evidence of the home’s updated heating and cooling systems visible from outside.Jacob Hamilton
Homeland Solar just installed Mirsky’s 14-kilowatt solar array in October, so he hasn’t yet seen the full benefits, but he expects it to provide about 80% of his yearly energy and he’s considering adding more panels. In the past two years, his maximum monthly energy bill has been about $335, he said, noting that included charging his electric car.
As for his heat pump system, the cost would be about $50,000 in today’s dollars, Mirsky said, noting his is more expensive than others because he drilled deep geothermal wells, which are more energy efficient, and his house is on the larger side. Someone with a smaller house and using an air-source heat pump or shallow coil system could potentially make the conversion for about half the cost.
Wayne Appleyard, a former city energy commissioner who has a net-zero, all-electric home, said his air-source heat pump system cost about $25,000.
Incentives coming
Residents and businesses who want to take the leap and invest in renewable energy and going all-electric could soon get five-figure rebates for doing so between incentives the city plans to offer and those the federal government offers.
The city also is planning to launch its own sustainable energy utility that could lead to creating city-owned solar microgrids to power neighborhoods and installing district geothermal systems under streets that residents and businesses could tap into, significantly driving down individual costs.
A 14-kilowatt solar array on the roof of John Mirsky’s home in Ann Arbor on Wednesday, Jan. 11, 2023.Jacob Hamilton
The city’s sustainability office is exploring the idea of district geothermal in the Bryant neighborhood, Missy Stults, the city’s sustainability director, said in November, indicating the city was seeking federal funding and it could take about a year to create a design and detailed plan.
“This is an important area of consideration and something staff are just starting to dive into the nuances of,” she said, indicating she’s been watching efforts in Massachusetts.
Ann Arbor officials acknowledge there will need to be gradual improvements to the power grid with the move to all-electric buildings, and grid reliability is going to be important. The city also is promoting backup battery systems to pair with renewable energy to ride out grid outages.
While many Ann Arbor residents could afford to upgrade their homes, the city acknowledges lower-income residents will need more help for an equitable transition. To that end, the city proposes putting an extra $750,000 per year from the city’s new climate-action millage toward helping low-income residents.
The sustainable energy utility the city plans to set up also could pay upfront costs and residents could pay back those costs through utility bills. Homeowners also can roll improvement costs into their mortgages or borrow through Michigan Saves.
‘We have the technology’
As for a ban on gas in new construction, if Ann Arbor goes it alone, some have expressed concerns it could push development outside the city and work against goals to add more housing in the city.
City Council Member Erica Briggs, D-5th Ward, raised the issue at a recent Energy Commission meeting, questioning the impact that could have on sustainability and affordability goals.
“I suspect that as strongly as all of us feel around a ban on gas ... we need to make sure that if we make those steps, that we’re doing our due diligence, making sure that we are on good legal ground, but also what are the implications,” she said.
Whether the city has the legal ability to ban gas is still being debated.
An electric heat pump dryer at John Mirsky’s home in Ann Arbor on Wednesday, Jan. 11, 2023.Jacob Hamilton
Energy Commissioner Claire McKenna, a UM doctoral student studying the transition from fossil fuels in residential heating, argues the city has a responsibility to protect people from the health effects of burning gas in homes and businesses. A zoning ordinance to end use of gas in new construction is imperative to uphold that and is a realistic, functional strategy to meet A2Zero goals, she said.
“As a building engineer, I have studied the feasibility and supported the design of all-electric buildings of all scales, from single-family homes to university lab buildings, hotels and high-rise office buildings in cold climates,” she said. “We have the technology to provide the heating, hot water and cooking demands for all use types, and we have the modern standards in place for energy efficiency, like air sealing and insulation. Appropriately, the state of Michigan is looking to adopt an even more efficient building code this year, reducing the electrical demand of our buildings and keeping harmful pollution out of the air as the city continues to move to greener sources.”
Ann Arbor is a leader but would not be the first U.S. city to ban gas in new construction, McKenna noted.
“Technical feasibility is no longer the most important question,” she said. “The question now is which developers and builders are going to step up and deliver?”
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