Elizabeth Stewart-Severy / Aspen Journalism
The path to carbon neutral in Pitkin County leads through residential construction.
Recent changes to Pitkin County’s land-use and energy codes hold new and renovated residential buildings to strict efficiency standards that officials say will significantly reduce greenhouse-gas emissions. But it is not clear by how much.
Last month, the Pitkin County board of county commissioners adopted the Home Energy Rating System (HERS) — a program to measure home efficiency — and set strict energy requirements that apply to new construction and remodels and additions over 1,000 square feet.
Homeowners with large rooftop solar installations — those that produce 10 or more kilowatt hours (kWh) — must also install battery systems to store some of that power. It’s a change that means both thousands of dollars in expenses and some energy independence for the homeowner, and could eventually allow Holy Cross Energy to use that energy when it’s most needed.
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“We’re trying to come in line with climate action and be more responsible with our buildings,” said Cindy Houben, director of community development for Pitkin County.
Buildings account for 53% of greenhouse-gas emissions in Pitkin County, according to a 2017 greenhouse-gas inventory produced by the Community Office for Resource Efficiency (CORE).
More-efficient buildings will mean fewer greenhouse-gas emissions, Houben said, but the county does not have projections about how much of a difference the new changes will make.
Brian Pawl, chief building official for Pitkin County, said he tried to work with CORE to come up with a model to predict changes, but it proved too difficult.
“It’s really hard to pinpoint what difference our changes will make,” Pawl said. “The hopes would be to see it reflected in the amount of emissions.”
He added that tracking emissions will be easier under the new code, since it uses the HERS index, an industry-standard score.
A typical home in the U.S. is rated 100 on the HERS 150-point index. The lower the score, the more efficient the home. Older, drafty homes fall closer to the top of the index, while newer homes tend to be better insulated, with lower HERS scores.
Pitkin County will require that homes receive a score of 60 or lower, before on-site renewable energy lowers that score to 30 or lower. Pitkin County calls this effort Net-30, a play on net-zero, which is expected to be the county’s requirement by 2030.
Pawl estimates that there are between 15 and 20 new homes built each year in the county and potentially hundreds of remodels that will have to comply with the new requirements. A local study of sample new houses averaged a score of 58.
“A lot of where the current code is lacking is addressing existing inventory,” Pawl said.
Older buildings tend to suck more energy. Eventually, Pawl said, there will be enough turnover that most homes in the county meet current efficiency standards.
To move the needle on emissions from buildings, “it’s going to take decades,” said CORE executive director Mona Newton. “Existing building stock is a real challenge.”
Pitkin County has long required that energy-intensive construction, including driveways with snowmelt systems, be offset with onsite renewable energy or payments to the Renewable Energy Mitigation Program. Now, the county also will require that homeowners with larger renewable systems — those that produce 10 or more kWh — install home batteries to store as much as 25% of that energy.
Pawl said it’s hard to know how many homes might be affected by the new requirement, but it’s likely that homes larger than 5,000 square feet or with extensive snowmelt systems would have to install storage.
When homeowners install rooftop solar systems, unless they choose to be off the grid with specialized technology, they remain on the grid and the energy produced on-site feeds back into the grid.
The new storage requirement provides some independence and resilience to individual homeowners, and it also could eventually help Holy Cross Energy — which supplies most of the upper Roaring Fork River valley with electricity — to manage renewable energy during peak demand.
“(Holy Cross is) looking at ways for people to have storage at peak times so we don’t have to build more infrastructure,” Houben said. “If we’re able to have storage and not have to build additional lines, then it’s just better for the community in general.”
The cost for the individual homeowners, however, will be significant. Home batteries cost thousands of dollars, and Pawl said the battery storage might, in some cases, cost nearly as much as the rooftop solar panels. But the long-term return on the investment should make it worth the upfront cost, he said, and homeowners will gain some independence.
“That’s the big future goal — is to be a little bit more resilient and have the ability to be independent,” Pawl said.
Also, he said, the current changes lay the groundwork for the county to require net-zero buildings by 2030. By then, technological improvements will make it easier to reduce or eliminate greenhouse-gas emissions from buildings.
“We’ll hope that the industry’s caught up,” Pawl said, “and there’s better panels out there and better opportunities and better battery storage and those prices have come down and we can be even more creative.”
The new building requirements go into effect in late July.
Aspen Journalism is a local, nonprofit and investigative news organization that collaborates with The Aspen Times and Aspen Public Radio on coverage of environmental issues. For more, go to aspenjournalism.org.