About two-thirds of the single-family homes built over the past five years in unincorporated Pitkin County have included at least one “exterior energy load” — such as a snowmelt system, pool, spa or heat tape — that requires mitigation under a program promoting renewable energy. Most of those properties installed a snowmelt system, a convenient but energy-taxing feature.

“Melting snow outdoors is obviously very energy intensive. You’re trying to make a surface be warm enough to turn ice to water when the temperature outside is that of ice,”  said August Hasz, president and principal engineer at REG, a Crested Butte-based engineering firm, who has been consulting with Pitkin County. “It’s a phase change, it takes a lot of energy.”

Property owners who want a snowmelt system or an outdoor pool or spa must either install on-site renewable-energy generation or pay a fee that supports green energy projects elsewhere, under the terms of the 23-year-old Renewable Energy Mitigation Program (REMP). Fees generated support the Community Office for Resource Efficiency (CORE), a nonprofit that provides grants and rebates for renewable energy. However, mitigation strategies that offset all exterior energy use have not always been possible or sufficient. Local governments are adopting and considering additional measures to help meet climate goals, including potentially reducing the maximum allowed house size in Pitkin County.  

The county and the city now each administer their own REMP programs. Pitkin County added electric heat tape — used for melting snow and ice from roofs, gutters, downspouts and exterior piping — to the list in 2020 of exterior energy loads requiring mitigation. Starting on April 1, Aspen’s REMP also applies to heat tape and outdoor gas fireplaces and heaters. Spas of 64 square feet or less are exempt in both jurisdictions.

An analysis of REMP data by Aspen Journalism shows that Pitkin County issued 79 REMP permits for single-family homes — including new construction on an empty lot and scrape-and-replace construction — out of a total of 119 single-family home construction permits issued between 2018 and 2022. There were also 20 REMP permits for additions to existing properties. The city of Aspen issued 89 residential REMP permits, including 47 building permits, 41 change order permits and one for a building-repair, from 2019 through 2022, out of a total of 535 single-family home permits, meaning REMP projects in the city have been occurring at a lower rate than in the county.

Snowmelt uses double the energy per square foot of the average home

The most common REMP feature over the past five years is snowmelt systems, with 49 of them averaging 2,439 square feet that were permitted at new and rebuilt single-family homes in unincorporated Pitkin County, and 11 systems averaging 1,366 square feet added to existing properties. City of Aspen permit data shows 16 snowmelt systems added to Aspen residences between 2019 and 2022; however, data provided by the city doesn’t say what exterior amenity was installed for 70 of the 89 issued permits due to changes in the city’s record keeping process over the years. 

“It’s such a luxury home market,” Aspen’s chief building official Bonnie Muhigirwa said. “There’s other climates that are similar to Aspen, but if they don’t have the luxury homes, you probably wouldn’t see people investing in snowmelt systems just because that’s such an expensive way to do snow remediation.”

The energy use of a square foot of snowmelt is about double what an average American home consumes per square foot, according to Hasz. An average American home consumes about 40 to 44 thousand British thermal units per square foot per year, while the REMP calculator estimates a square foot of snowmelt to be using 83 kBtu in energy per year.

REG also compared the carbon dioxide emissions associated with two different methods of clearing snow on sidewalks for the town of Crested Butte. The study shows that snow removal with snowplows, snowblowers and trucks uses about 70 to 90 times less carbon than melting the snow on the sidewalks. 

Besides snowmelt systems, 25 spas, 21 outdoor pools and 16 heat-tape systems were installed at new, rebuilt and existing houses in unincorporated Pitkin County between 2018 and 2022, while 14 spas and three pools were added in Aspen between 2019 and 2022. Some permits included multiple REMP exterior energy loads on the same property.

Lack of space prevents mitigation measures from successfully offsetting energy use

When a property owner decides to install one of the exterior amenities covered by REMP, they have the option to offset their exterior energy use through on-site renewable energy, such as solar panels (photovoltaics), solar hot-water systems or ground-source heat pumps. If the property owner elects against sufficient on-site mitigation, they must pay a fee.

Solar panels are the most popular solution to offset energy use because they’re the easiest to install and the most cost effective, Pitkin County chief building official Jeff Erickson said.

Forty-four new, rebuilt and existing home projects chose solar panels to offset their exterior energy use over the five-year time period. Only two home projects installed solar hot-water systems while seven projects opted for a ground-source heat pump. 

The mitigation strategy used by each applicant wasn’t available for the city permits.

Although most people opt for renewables, they still need to have sufficient space on their property to install enough solar panels to effectively offset their energy use. 

“They have to install a lot of solar, which means they need a roof that can accommodate that or a parcel that can accommodate a ground-mounted array,” Erickson said.

As the county moves toward a goal of net-zero emissions from new residential construction by 2030, Erickson said that homeowners will need to find sufficient space to offset their interior energy use first and that they may not have enough space left to cover exterior features. 

The actual energy use of each of the REMP installations is often underestimated by the county and city calculators, according to Hasz. The modeling software assumes, for example, that heated pools will be covered, but often they are not, using more energy than expected.

A ground-mounted solar array peaks out above a berm at a home on Willoughby Way in unincorporated Pitkin County.
A ground-mounted solar array peaks out above a berm at a home on Willoughby Way in unincorporated Pitkin County near Aspen. Solar panels are the most popular solution to offset energy use under the REMP program because they’re the easiest to install and the most cost effective. While most people opt for renewables, they still need to have sufficient space on their property to install enough solar panels to effectively offset their energy use. Credit: Laurine Lassalle/Aspen Journalism

Paying into the REMP fund

In Pitkin County, 33 newly built single-family homes and 18 existing houses that applied for a REMP permit between 2018 and 2022 chose not to install any renewables for their projects. In these cases, or when the REMP calculator estimates that the renewables proposed will be insufficient to offset the exterior energy use, homeowners must pay a fee.

The county recorded a total of $3.6 million in REMP fees in the past five years, including $2.2 million in 2022. On average, REMP fees reached $61,000 per permit for single-family homes and $23,500 per permit for additions. But some of the fees end up being refunded.

Erickson and Alex Sanchez, county analyst, said applicants may decide during the building phase, which can take several years to complete, to install more renewables than they initially proposed. If that’s the case, they can get a refund of their REMP fees up to 120 days after the issuance of the certificate of occupancy. 

The city data shows a total of $2.5 million paid in REMP fees by residential property owners from 2019 through 2022 in lieu of on-site renewable mitigation. The city has collected about $18.3 million in total REMP fees since 2000.

“It’s always been pay to play,” said Cindy Houben, Pitkin County’s former community development director. “You can pay for it and you get what you want through the REMP program to a certain extent.”

Muhigirwa said she doesn’t think the evidence shows that REMP has reduced the amount of snowmelt or pools being installed. “There might be some homeowners that [REMP has] discouraged them from doing as large of the system due to the cost,” she said. “But, again, because of our luxury market, I would say that the good thing is that we are getting the offset.”

The city and county use the REMP fees to fund other environmental projects. “We’re getting additional renewable on-site or we’re getting that money that can be used by CORE and other programs to offset that energy use,” Muhigirwa said.

CORE, founded in 1994, has received about $16.5 million from REMP since 2007. The nonprofit organization offers grants and rebates to people who may be unable to afford to install a solar system or energy upgrades, and also helps affordable-housing projects and schools install solar panels and energy upgrades. 

A 2015 report shared by CORE — the latest CORE report on REMP data — noted that onsite renewable-energy systems installed through REMP were able to offset about 64% of exterior energy use from 2010 to 2014. The report estimated that CORE’s REMP-funded projects saved a total of 45.5 billion Btu per year, equivalent to the consumption of about 393 average homes in Aspen’s cold climate. 

A new single-family home on Miners Trail Road in Aspen
A new single-family home on Miners Trail Road in Aspen will feature 1,081 square feet of snowmelt and a 37-square-foot outdoor spa. This property is among Aspen’s 89 REMP residential building permits issued from 2019 through 2022. Credit: Laurine Lassalle/Aspen Journalism

Snowmelt and other exterior energy loads are more common in larger homes

Although CORE, using REMP funds, helps offset local energy use, “[REMP is] not enough,” said Mona Newton, CORE’s former executive director and co-chair of the Pitkin County Community Growth Advisory Committee.

Building codes may require new homes to be more energy efficient, but luxury homes use more energy per square foot. 

A REG report “speculates” that this is primarily driven by amenity loads, which it defines as energy uses that are not seen in average American households. These include humidifiers, water fountains, audio/visual and information/technology systems, in-floor heating, large air-filtration systems and large cooking ranges, as well as outdoor energy uses such as snowmelt, pools, spas and heat tape. 

“The use of snowmelt, spas, outdoor pools and heat tape increase dramatically as home size increases,” noted the REG report that analyzed REMP data. 

This is one of the reasons behind the Community Growth Advisory Committee’s recommendation for shrinking the maximum-allowed square footage of new homes in unincorporated Pitkin County by about 40%. 

The committee, which consists of 26 appointed members, has spent the past 10 months working toward a series of recommendations that will be presented to Pitkin County Board of County Commissioners and Planning and Zoning Commission on June 6 to help the county meet its 2050 climate goals. The committee proposes limiting the square footage of new homes to between 8,750 and 9,250 square feet, down from the current maximum in most of the county of 15,000 square feet. 

Larger homes, defined as homes over 5,750 square feet, generate substantial traffic and higher greenhouse gas emissions per square foot than smaller houses due to construction, maintenance and more-frequent use of energy-intensive amenities. The larger the home, the greater the energy use per square foot, according to the report.  

Although larger homes represented 13% of the single-family home inventory in unincorporated Pitkin County in 2019, they accounted for 43.4% of the total residential-energy-use emissions of that same year, according to a white paper that county staffers compiled in November for the committee. 

However, the REG report also stated that if home size is limited but amenity loads are not addressed, the energy use per square foot of the homes at the top end of the allowed size range may still increase.

Pitkin County Community Growth Advisory Committee with its 26 appointed members.
The Pitkin County Community Growth Advisory Committee, made of 26 appointed members, has spent the last 10 months working toward a series of recommendations that will be presented to Pitkin County Board of County Commissioners and Planning and Zoning Commission on June 6 to help the county meet its 2050 climate goals. Credit: Laurine Lassalle/Aspen Journalism

Limiting energy use with actual caps

Snowmelt systems in Pitkin County are capped at 6,000 square feet per parcel. On April 1, the city capped exterior energy use at 200 million Btu per year, which represents either 2,414 square feet of snowmelt, 603 square feet of pool, 466 square feet of spa or 3,125 square feet of heat tape. 

In Aspen, all city-owned buildings, commercial buildings over 15,000 square feet and multifamily buildings over 20,000 square feet are now required to participate in the CORE and “Building IQ,” a city-led program that collects energy-use data and helps identify energy-saving solutions.

New homes in the county have been required since 2020 to meet a maximum energy rating index (ERI) of 60 before renewables or a maximum ERI-30 after the installation of on-site renewables. This means that new homes are required to be 70% more efficient than a home built according to 2006 International Energy Conservation Code standards.

Houben said people may get the false idea that if all their energy is coming from a renewable source, they may not need to cut back. “[But] you just have to build more stuff. And nothing’s free,” she said. “There’s always an impact. … There’s a cost to that, not just a monetary cost, but there’s a cost to our environment.”

This story was published in the Aspen Daily News on May 28.

Editor’s note: This story was updated to correct an interviewee’s job title.

Laurine Lassalle is Aspen Journalism’s data desk editor, where she works to catalogue and analyze local public data. She also heads our our “Tracking the Curve” project, documenting COVID-19 in Pitkin,...