Squeezing the carbon from homes

New regulations in Colorado resort county seek to drive carbon from homes

by Allen Best

Thirty years ago, an oil-flush Arab prince built a 56,000-square-foot compound just outside Aspen, in unincorporated Pitkin County. The wealthy then did pretty much what they wanted in the mountain playground.

Aspen still draws the billionaires, their private jets lined up at the local airport like SUVs outside a Costco. Unlike the jets, with their lavish thirst for fossil fuels, however, houses set amid the serviceberry-covered hillsides outside Aspen now face limits. New homes cannot exceed 14,000 square feet.

New regulations that took effect today, July 30, aim for a deeper rethinking yet about achieving comfortable living without imported energy. It’s part of a broad examination of how to reduce greenhouse gas emissions associated with the built environment.

Aspen has often been at the forefront of innovation. It had the first electric streetlights between the Mississippi River and the West Coast in the 1880s. And a century later, even before the Saudi prince built his castle, energy visionary and Rocky Mountain Institute co-founder Amory Lovins demonstrated what was possible on a modest budget: bananas—yes, a banana crop—not more than 20 miles from Aspen. Crucial was thoughtful design. This isn’t all about money.

Pitkin County and Aspen have been on this path for several decades, if at first with different motivations. In 2000 came the Renewable Energy Mitigation Program (REMP). New houses of more than 5,000 square feet and those places with heated driveways and outdoor swimming pools had to offset the presumed impact of the luxurious use of electricity with on-site renewables.

Most homeowners have chosen the alternative, paying into a fund that provided grants for defraying energy efficiency and renewable energy projects elsewhere in the Roaring Fork Valley. Nicknamed the Robin Hood program, it was a response to the adverse impacts of mercury, nitrous oxide, and other harmful emissions from coal-burning power plants. Other mountain resort communities in Colorado used that program as a model for their own programs.

Concern about greenhouse gas emissions drives the new regulations. Pitkin County in 2019 declared a climate emergency, one of six such resolutions in Colorado and 50 nationally. This is an effort to match that reality.

The new regulations in Pitkin County employ the Home Energy Rating System, or HERS, a measure of energy efficiency. The lower the number, the greater the efficiency. Older, drafty, and uninsulated houses might score 150 or even 200. A house built satisfying the 2006 International Building Code is defined as a HERS of 100. Pitkin County’s program requires HERS scores of 60 or better on all houses of more than 1,000 square feet.

The HERS score of 60 required by Pitkin County’s new regulations is good but hardly heroic. Most new homes in the sprawling new suburbs of the Front Range already hit that mark. During the next decade, Pitkin County hopes to ratchet down HERS ratings to zero by 2030 as techniques and materials improve and architects and builders gain experience.

Other places in Colorado are doing perhaps even more to squeeze carbon from housing. In one respect, the regulations of Boulder and Boulder County are more rigorous. They require any new or rebuilt house of more than 5,000 square feet achieve a HERS rating of zero. Requirements recede as house sizes decrease. A house of 1,500 square feet or less need only hit a HERS score of 60. Boulder County plans to increase requirements to require all new houses to achieve net-zero HERS scores beginning in 2022.

Ron Flax, the chief building official in Boulder County, says the most important thing you can do to reduce carbon emission from housing is reduce the square footage per capita. “As the houses get bigger, they do consume disproportionately more energy, so that’s why we scale it up,” he says.

Even without mandates, some developers have been shedding fossil fuels from housing. It’s not just high-end housing. In the Denver suburb of Arvada, net-zero defines the Geos Neighborhood. In Westminster, another suburb, a homeowner had the natural gas line stubbed after executing the innovations that made it unnecessary.

Big houses can be found in not just high-end mountain resorts. This house is located in the Denver-Boulder suburb of Arvada. Photo/Allen Best

But there’s a bigger picture, one only starting to be discussed. That’s the carbon emissions caused by the materials that go into houses and other buildings. The larger the house, the more the materials, the greater the carbon footprint. And the size of houses has skyrocketed in recent decades.

“If I build a big, net-zero energy home and think I have boasting rights—that’s not true at all,” says Flax. “There’s no such thing as a large, environmentally sensitive home.”

A bill introduced into the Legislature—but then stalled in the covid-crimped session—would have established a maximum acceptable global warming potential for each category of eligible materials used in a public project. Sen. Chris Hansen, D-Denver, says he intends to introduce the concepts contained in SB 20-159 in the next session.

These efforts should be seen within the context of broader, economy-wide decarbonization goals. Colorado in 2019 adopted a law that identified a target of 50% reduction by 2030 and a 90% reduction by 2050. It’s not enough to close coal-fired power plants. Getting there will require rethinking our buildings. New houses will be the easy part. Retrofitting older houses and buildings—that will be the monumental challenge.

Long-time Colorado journalist Allen Best publishes an e-magazine called Big Pivots, from which this was extracted. You can sign up to get free copies

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