Image by New Frameworks, a prefabricated straw bale panel company
Building a custom house using new — or not-so-new — sustainable building materials can help fight climate change. Recently, the sustainable design community has been doubling down on carbon, trying to reduce the carbon footprint of manufacturing processes and of buildings themselves.
At Artisans Group, we’ve been committed to this process since before 2008, when we first introduced Passive House principles into our work. Since then, we’ve designed dozens of homes that have been built, from Anacortes to Austin.
We’re still on the cutting edge of sustainability and we want to stay there, largely because we operate in harmony with this sentiment by Henry David Thoreau:
What is the use of a house if you haven’t got a tolerable planet to put it on?
Right now, scientists warn that our planet will become intolerable for much of humankind — if we don’t do something soon.
The culprit is carbon, a compound that has, up until (relatively) recently, remained in check in our environment.
Because of human activity, however, carbon is now being released into our atmosphere and oceans at a rate that is “hundreds to thousands of times faster than it took to bury it,” according to the University of California at Berkeley. “[T]he carbon dioxide released from the burning of fossil fuels is accumulating in the atmosphere, increasing average temperatures through the greenhouse effect, as well as dissolving in the ocean, causing ocean acidification.”
Embodied Carbon vs. Operational Carbon — And What It Means For Building Materials
There are two kinds of carbon you can measure in any structure, operational carbon and embodied carbon.
Operational carbon is the amount of energy that is used to operate a building. Think of the heating, cooling, electrical, and other systems that make a house functional and comfortable. We seek to reduce operational carbon through Passive House design.
Embodied carbon is the amount of energy it takes to extract, refine, produce, transfer, and install a material. Reducing embodied carbon makes the whole process of building a house more sustainable and can even be part of the solution by helping capture carbon from the atmosphere. (Some materials actually capture carbon for the duration of their lives!)
Let’s talk more about embodied carbon, starting with insulation. Carbon Smart Materials Palette lists a range of materials used in insulation. At one extreme is extruded polystyrene (XPS), a material derived from petroleum. It emits 6,735 kgCO2.
Compare that with straw bale insulation, a rising star among sustainable building proponents. It sequesters 7,437 kgCO2. Between these two extremes are a range of carbon-neutral or even carbon-negative materials to choose from.
The same is true of other building materials. The carbon footprint of aluminum, for instance, is extremely high while rammed earth, an age-old material for wall construction that is gaining in popularity, has one of the lowest carbon footprints of any building material.
Every building materials choice has the potential to reduce the embodied carbon of your project.
What Sustainable Building Materials Reduce Embodied Carbon?
If you’re building a house, one of the most impactful things you can do as an individual is to build an energy efficient home. Once you have established that goal the next is to choose and source materials that reduce embodied carbon. Choose manufacturers, suppliers, and even shipping services that work to minimize carbon emissions — it can all make a big difference.
There are lots of options out there, but today we’re highlighting five that have the potential to make a significant positive impact on embodied carbon by sequestering carbon or by taking in more carbon than they give off.
Five Materials We Love
Wood. We use it all the time for framing and structure, as well as flooring, wall and ceiling finish materials, siding, cabinets, and built-in storage. Whenever we can use solid wood we love to but we also incorporate engineered hardwood to increase dimensional stability. Ever heard the term “wood is good”? Wood’s low carbon footprint, availability, and versatility make it an excellent sustainable choice.
Cork. We use cork most often as a flooring material in our projects but we’ve also seen it as a wall finish or as a backing material to help reduce echoing. Cork also has great thermal properties so it can be used as an alternative for conventional insulation. Cork can be harvested multiple times from a single tree and is also recyclable and biodegradable.
Straw Insulation. This is a material we have not yet used, but we look forward to partnering with New Frameworks to construct a residential project someday using straw bales as insulation. Straw bales act as the walls of the building but are mainly used for their insulative, rot-resistant, and fire-retardant properties.
Concrete Additives. On its own, concrete is rather high on the carbon scale. Right now, we use it as minimally as possible, typically only in foundations and retaining walls of new buildings. It’s so thoroughly integrated into our industry and into how we understand structures that it’s difficult to get away from.
However, mixing vegetation and additives with concrete can reduce its carbon footprint while maintaining its structural properties. Popular additives include fly ash, algae, hemp, and perlite.
Rammed Earth. One of the most beautiful — and most low-carbon — materials, rammed earth is used for structural and non-structural wall construction. It is just what it sounds like: walls built from soil components such as damp sand, gravel, clay, and lime that are made by ramming these layered components between forms. Insulation may or may not be sandwiched in the middle. These walls are made to be left exposed, on either (or both) interior and exterior. We’re keen to use it in a project!
How Do I Reduce Carbon In My Building Project?
If you’re building a house, the first thing you can do is get educated about your options. (You’ve started that process. Nice work!)
The next step is to partner with an architecture firm that is dedicated to sustainable, carbon-reducing practices so you can work with a team that shares your goal of building a low-carbon structure.
To reduce embodied carbon in your project, prioritize existing and new sustainable building materials in your project:
- Source naturally and locally, within a 200-mile radius of the project whenever possible.
- Look for FSC-certified wood suppliers.
- Use reclaimed materials.
- Verify the ingredients in a material.
- Consider the lifespan of each material. What happens to that flooring, siding, or countertop when it gets removed from a building?
- Support businesses that practice environmental and social equity.
Solving the climate crisis is the greatest and most complex challenge that Homo sapiens have ever faced. The main solution, however, is so simple that even a small child can understand it. We have to stop our emissions of greenhouse gases. And either we do that or we don’t.
Greta Thunberg: Our House Is On Fire!, World Economic Forum, 2019
Who We’re Learning From
We’re privileged to learn from groups and individuals who prioritize low embodied carbon and work to make our built environment more sustainable.
Love | Schack Architecture, a sustainable firm that has utilized straw insulation successfully in the harsh winter climate zone of Montana.
The Passive House Northwest team, led by Greta Tjeltveit. They organized a micro conference in 2023 to talk about embodied carbon and invited vendors such as Sustainable Northwest Wood, a local mass timber company, and Thermacork, a local cork insulation manufacturer.
Skylar Swinford, a former energy modeler for our team, spent more than a year working to prove that Passive House not only reduces operational carbon but also reduces embodied carbon by default. Skylar built the tool OCEC, a boon for sustainable architects.
Posted on June 01, 2024
