How sustainable builders consider a home’s entire carbon footprint
Commercial and multifamily buildings have focused on reduced carbon footprints in recent years, although the concept is relatively new for homebuilders — especially measuring something called embodied carbon.
Most homebuilders are familiar with operational carbon, which refers to the greenhouse gas emissions from a home’s energy use after it’s built. However, embodied carbon looks at all the energy it took to build the home in the first place. That includes the energy that went into manufacturing and transporting its materials, as well as during the act of its physical construction. Right now, that number is higher than most green-focused homebuilders probably realize.
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For example, the average U.S. home produces 45 kilograms of CO2 per square meter annually from an operational perspective, according to a 2020 University of Michigan study. But a recent Canadian report found embodied carbon accounted for 250 kilograms of CO2 per square meter in residential buildings, or more than five times as much.
That means even the most energy-efficient new homes built today have already contributed five years’ worth of greenhouse gas emissions to the environment before their new owners move in. Put another way, the embodied carbon of constructing the 1.6 million homes built in the U.S. last year put the same amount of greenhouse gases into the atmosphere as operating 22 million cars for an entire year.
Think Wood reimagines the possibilities of wood by providing single-family design and build resources to contractors. Wood’s environmental, biophilic and health benefits can offer market differentiators that boost a project’s value. You can discover project profiles, design tools or free project support at thinkwood.com.
Think Wood shared their conversation with Aaron Smith, CEO of the Energy & Environmental Building Alliance, as well as his own firm GreenSmith Builders. Smith is passionate about sustainable and low carbon construction.
Think Wood: Tell us about EEBA. What is your mission?
Aaron Smith: In 1982, a group of builders from the U.S., Canada and Scandinavia came together and said, “Let’s try to build more energy efficient homes.” We’ve seen that transition to energy efficiency through building science and education, but today I would say the focus for EEBA’s builders is healthy, electric, resilient, decarbonized and net zero.
Think Wood: We’ve heard a lot about net zero energy homes, but EEBA also has a focus on embodied carbon?
Smith: We’re talking about both embodied and operational carbon now. The primary thing we’re trying to do is get people educated about what decarbonization is, what an environmental product declaration is, what a life-cycle assessment is. When I look at two different materials, what does it mean to think about the embodied carbon in that material?
Think Wood: Why does lowering carbon emissions matter to builders?
Smith: It matters for a few reasons. First, builders have a pride of craftsmanship and they extend that same care to thinking about the environmental impact of the materials they use because they’re thinking about the future. My grandfather was a builder and he always asked, “Are you happy with what you did? Because it’s going to be there for 100 years.”
And, we’re starting to see carbon codified across North America. California, Oregon, Washington, they’re headed in that direction. I’ve got a buddy in Texas who builds 1,000 homes a year. This year, his investment firm called him and said 20% of the product that you build for us now needs to be net zero. That’s not quite to decarbonization yet, but when finance starts telling production builders you need to do this, that’ll be a game changer.
Think Wood: What steps can builders take in the design phase to achieve low carbon homes?
Smith: EEBA members asked us to research the best tools accessible to builders for calculating operational and embodied carbon. We counsel them to put their houses into a building information modeling system like AutoCAD or Revit. You can import that into some whole-building life cycle analysis tools and start to generate a carbon footprint for the home design. We’ve added kilograms per ton of CO2 for your home to EEBA’s intake form because we want to start benchmarking it, too. In the future, we’ll start to compare those benchmarks across the industry.
Think Wood: Can you tell us about your Gateway to Zero program?
Smith: There is a path to zero for everyone, but with so many programs, guidelines and standards, finding the one that’s right for you can be overwhelming. Though we know that “getting to zero” is not always a linear process, we’ve organized resources in categories from “base energy code” to “zero embodied carbon.” EEBA can help you become a more sustainable builder from wherever you’re starting. You may be at code today; you may then want to look at the Energy Star program. It’s free, and it’ll make you a better builder. And then you might want to move to one of the zero energy programs out there. We provide support throughout this entire journey.
Think Wood: Does building with wood provide any advantages when low carbon construction is the goal?
Smith: Once you’re educated on how material selection impacts a home’s carbon footprint, I think it’s a little bit “back to the future.” You start to say, “Well, instead of putting the steel beam in, I could put a cross-laminated timber beam in and have a carbon sink instead of a huge carbon cost to my home.” To reduce carbon, I think it’s going to be a return to wood in a lot of cases. Homes can literally be a carbon sink instead of emitting carbon.
A Trent University graduate student’s study compared the net carbon emissions of the same building using different materials in each modeled scenario.
– The results were drastically different depending on the products used:The highest emission scenario used clay tiles, steel joists, high-VOC carpets, steel framing, cement brick for cladding and high-embodied carbon concrete for the slab.
– For the same structure built to the same level of performance (to local code), the net carbon emissions were lowered by 144 tonnes by using trusses and asphalt shingles, drywall and mineral wool, wood framing and drywall, fiber cement for the cladding and an average concrete with mineral wool for the slab.
Thrive Home Builders
Thrive Home Builders have made energy-efficient and eco-friendly features central to the design and construction of their clients’ homes. This includes achieving environmental certifications like LEED, Indoor airPLUS, Zero Energy Ready Homes and Energy Star. The Denver-based homebuilder has a successful track record delivering zero operational energy homes and is now turning its attention to their homes’ embodied carbon impact.
Thrive is pioneering a new design process that evaluates the use of carbon measurement tools and technologies like BIM to better understand the embodied carbon impact of materials and how it can curb emissions through design and offset measures. The firm has been recognized by the U.S. Department of Energy’s Housing Innovation Awards since 2017 for its commitment to the department’s Zero Energy Ready Home program.
“Thrive Home Builders delivers energy-efficient homes with a mission focused on healthy and local solutions,” said Bill Rectanus, chief operating officer. “We’ve been making conscious choices in the design of our homes for 30 years to make them healthy for families, the environment and the planet. We think the carbon conversation is a great tie-in to what we are doing already — and we believe it’s becoming clear for our buyers: you can’t be healthy yourself without a healthy home and a healthy planet.”
With a mantra of “people, planet, purpose!” Bettr Homes is focused on the triple bottom line, while delivering sustainable build-to-rent homes designed to be high performance, healthy and resilient. The firm exclusively builds net-zero energy homes that meet certification standards like Zero Energy Ready Home, EPA Indoor airPLUS, Energy Star, LEED and Resnet HERS Index.
Bettr Homes’ vertically integrated business model positions the company to work well with real estate investment trusts to deliver affordable net-zero rental homes, expanding access to much needed entry-level, environmentally-sustainable housing. By attracting ESG-focused investors that perceive long-term benefits of healthy, affordable, low carbon homes, Bettr is demonstrating that sustainable home construction is not only good for the environment, but for the bottom line as well.
“What we’ve created with Bettr Homes is a triple-bottom line enterprise and we’re working with investors to add affordable net-zero homes to their rental portfolio — in doing so we’re creating healthy communities with a focus on decarbonizing the rental housing business. Its success is showing us, when you manage to an ESG standard, you create real value,” said Corey Donahue, CEO and cofounder of Bettr Homes.
Images (in order of projects) via Thrive Home Builders, SmithGroup and Jason Robinson and Bettr Homes