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Colorado bill proposes to add filter of global warming potential to state-funded buildings and roads

by Allen Best

Big Pivots

In 2019, Colorado legislators passed an impressive suite of laws that boldly staked out ambitions to dramatically decarbonize the state’s economy.

Now, the hard work is underway. In this year’s session, legislators have introduced dozens of bills that collectively seek to define the pathways for achieving this towering task. Closing down coal plants will not be enough. Every single component of the state’s economy produces greenhouse gas emissions.

HB 21-1303, a bill introduced in early May, seeks to use the state government’s purchasing power to nudge architects and contractors to make greenhouse gas emissions a calculation in selection of building materials. The state has spent $54 billion in the last decade on buildings.

This bill would apply this additional criterion to new buildings created with state funds. It was approved by the Colorado House Energy and Environmental Committee on an 8-5 party line vote on May 20 and the House Appropriations Committee the next day on a similar party-line vote. In both cases, the Democratic majorities prevailed.

California has adopted legislation to use state spending to begin steering the building market toward so-called green materials. Six states, including Colorado, have or will have similar bills under consideration this year.

Colorado’s bill takes a step beyond that of California or other states in that it would also require the Colorado Department of Transportation to begin using the filter of greenhouse gas emissions of concrete and asphalt when choosing road materials.

Rep. Tracey Bernett

This would be a huge step for Colorado, says a bill co-sponsor, Rep. Tracey Bernett, a Democrat from Boulder. “It’s very comprehensive, what we want to do with this,” she says of the bill.

The Polis administration supports the bill. “We think this is an important strategy for achieving the state’s carbon reduction goals,” said Will Toor, director of the Colorado Energy Office at the May 20 hearing. C-DOT also testified on behalf of the bill, as did several industry groups.

State Sen. Chris Hansen, a Democrat from Denver, submitted a similar bill in last year’s covid-shortened session, but it did not have the same scope. He is a co-sponsor of this year’s bill, as is State Rep. Barbara McLachlan, a Democrat from Durango.

Because of the fossil fuels typically used to produce steel and the emissions associated with concrete and cement, building materials themselves have a large carbon footprint. Too, there is carbon associated with the transport of materials. All would have to be calculated and used in the choice of building materials and specific product.

The bill, “Concerning Measures to Limit the Global Warming Potential for Certain Materials Used in Public Projects,” would have the Colorado Department of Personnel & Administration establish what the bill calls a” maximum acceptable global warming potential” for each category of eligible materials used in certain public projects under its purview. When projects go out to bid, this maximum would be included.

The Colorado Department of Transportation has a similar process in front of it, but with a little more breathing room as state engineers calculate what would be best.

Think of this as being akin to the social cost of carbon, a metric now being used by the Colorado Public Utilities Commission in evaluating electric resource plans submitted by utilities. That social cost adds the long-term costs of resource choices into the decision-making matrix.

This is from Big Pivots, an e-journal that tracks the energy and water transitions in Colorado and beyond. To subscribe, go to

House committee members heard abundant testimony in support – including from road builders and unions, along with several architects. They said that materials with lower global warming potential are already available and being used.

Why, if the free market is moving in this direction already, will a state law be needed?

“I think the bill has merit to the extent that the more we pay attention to this, the more likely we are to get favorable outcomes,” said Paul Hutton, a principal at Cuningham, a national design firm with an office in Denver’s LoDo neighborhood.

“We are just raising the bar and holding company and design firms and contractors accountable,” he said. “If we don’t make this an explicit measure, we’re not likely to make progress as rapidly as if we say this is something that matters.”

Global warming potential of materials has become a consideration for Hutton’s firm in just the last few years, and it isn’t for all design firms even now, he said.

A new building on the University of Denver campus uses timber in lieu of traditional steel and concrete. Photo/SA+R.

Thinking about buildings and their materials in light of the carbon footprint of materials plays out in different ways. One example is the timber building at the University of Denver, designed by Cuningham and project partner architect, Lake Flato. It eliminates the typical steel and concrete components in vertical architecture. Wood can be used with adequate structural integrity to heights of 17 floors, he says.

“Timber has a far lower embodied carbon than either concrete or steel,” says Hutton. “That’s a trend we’re starting to see in Denver and across the country.”

Another example comes from rural Colorado. At Blanca, a town at the foot of the eponymously named 14,000-foot peak in the San Luis Valley, a new school is being completed. Sierra Grande School will not burn propane for heating, as was the case with the former school.

The design begins with the maximum insulation of the building envelope. The ceiling’s R-value, a measure of insulation, is 65, and that in the walls is 49. Both are double the typical high R-values in building insulation.

But in insulation, there’s another consideration. What is the carbon footprint of the material? Hutton explains that insulation is plastic based and hence derived from petroleum. Different processes used for manufacturing, however, have varying emissions of greenhouse gases. Figuring out the specific insulation and the amount to use is something that a building designer must consider when calculating its global warming potential.

Even when concrete is used, there are variations. A story by the BBC earlier this month explained that we use more concrete than any other substance, except for water.

Cement is a bonding agent used to create concrete along with water, sand, and gravel. Essentially, it’s a glue, and it typically constitutes 10% to 15% of concrete. The critical agent in concrete is lime. It is obtained by heating calcium carbonate, usually limestone. High temperatures are needed, 1,450 degrees C (2,642 degrees F, or roughly enough to melt stainless steel).

This process yields calcium oxide, the critical agent in cement. From the rock it also unleashes carbon dioxide—and this is a big deal. Cement accounts for about 8% of the carbon dioxide we emit into the atmosphere globally. Aviation produces about 2.5% of emissions.

In this process, fossil fuels produce 40% of the carbon footprint of cement and the carbon dioxide released from the limestone 60%.

Techniques have been developed to reduce the carbon dioxide emissions associated with cement production. The BBC story details several of them. They include using substitute materials such as ash that can displace part of the cement without reducing strength. Another approach, if more expensive, involves using a different binding agent that does not produce emissions. A third approach, carbon capture, involves a 200-foot-long metal tube.

The Colorado Department of Transportation supports HB21-303, which would require the state to consider the embedded carbon in road materials in which state dollars are spent, including Highway 285 across South Park. Photo/Allen Best

Colorado has two cement plants, one at Lyons and the other at Florence. The Florence plant, operated by LafargeHolcim, an international company, has developed a cement that it says has fewer emissions of carbon dioxide.

The lower-carbon product, OneCem, was used by C-DOT in 2008 in reconstruction of U.S. 287, the highway that extends diagonally across Colorado from Springfield to Limon and also from Denver to the Wyoming border. The product was also used in building Interstate 25 south of Denver. Altogether, says LafargeHolcim, the product has been used on 600 lane miles of concrete paving in Colorado.

The Colorado Decarbonization Roadmap also mentions the company’s cement plant at Florence in a section on carbon capture, use, and sequestration. The company is said in the report to be giving “serious consideration” to employing carbon capture technology—perhaps as described above. The technology has proven too burdensome for widespread use in burning of coal for electrical production.

Representatives of LafargeHolcim and Castle Rock Construction Co., a builder of highways, testified in support of the bill.

Just how many buildings might this impact in any given year? Perhaps a few fewer than you might think. State universities, for example, have dozens and dozens and dozens of buildings. But relatively few get constructed using state funds.

This bill proposes a nudge, not a shove.

May 27 addendum: This bill was approved by the Senate Transportation and Energy Committee late Tuesday night, May 25, on a party-line 4-3 vote. The primary questions of dissenting Republicans were questions of elevated costs to highway construction. Cost of asphalt was a particular concern. Sen. Chris Hansen, once again a member of that committee, responded that this offered an opportunity to recycle asphalt. Andy Karsian, state legislative liaison for C-DOT, testified in support, noting that the bill provides a 3-year window while C-DOT puts together its approach.

Correction: The story had said the school at Blanca relied upon underground pipes, or geothermal. to provide warmth. That was incorrect. The budget did not allow for that, which required even more attention to the insulation in the building envelope.

Allen Best
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