sustainable and resilient design
Sustainable Building Materials
Hempcrete, derived from the hemp plant, is poised to become an important player in the green building industry
By Jason Takahashi
IN 2019, the total value of construction performed in the United States is projected to reach $1.3 trillion. Residential housing starts are estimated at 815,000. This incredible sum illustrates not only the pace in which residential and commercial development continue to grow, but the sheer magnitude of the market. The influence of sustainable building materials within this market is the focus of this article.
Industry at this scale comes with incredible costs. Approximately half of our global energy supply is consumed through constructing, operating, and maintaining buildings worldwide. Thanks to continued adoption and advancements in renewable energy sources, operational energy costs of buildings has decreased over time. However, there has been little interest in curbing the impact of sourcing, processing and transporting the building materials used. Finding solutions for these embodied costs represent the next frontier of smart, sustainable building technology.
building with smart materials
Natural building materials and techniques that inherently reduce environmental impact are plentiful and are of course nothing new. Myriad methods utilizing locally grown and sourced materials, from rammed earth to straw bale construction, have existed for millennia. The key factors which decide if a natural building material is smart enough for 21st-century construction and climate goals include the ability to be locally sourced, net-zero carbon, and structurally sound, all while promoting lower operational costs. Interestingly, perhaps the most promising of candidates comes from America’s long-lost fiber, the hemp plant.
A five-decade long ban on hemp cultivation in the United States was recently lifted as a provision in the 2018 Farm Bill. Hemp’s fall from grace as a quintessential crop revered by American icons such as George Washington, Thomas Jefferson and even Henry Ford is a mystifying tale. One which we unfortunately do not have time to tell here. Nevertheless, utilizing hemp as a building material has not been lost on many of our Western allies.
Starting in the early 1980s, French builders resurrected a form of building material known as béton du chanvre — now called hempcrete— which dates to circa 500 A.D. The process is simple: a mixture of crushed hemp hurd (material inside the stalk), water and lime. While often seen as a low-tech building solution, the technology has progressed in recent years to include pre-fabricated bricks and panels that have been employed in residential and commercial buildings across Europe and Canada.
enter Escher Design
I recently caught up with Bob Escher, an architect and AIA member based in Dorset, Vermont. With 30 years of experience specializing in high-end custom homes, country clubs and libraries, Bob recently started designing small-scale hempcrete projects. After years of searching for green building materials, Bob was drawn to hemp by his son Alex. As of today, the size and scope of the projects Bob and Alex have built using hempcrete are still small — but they’re certain the day for widespread disruption draws near. Here’s what Bob and Alex had to say…
JASON TAKAHASHI Thanks so much for taking the time to chat, gentlemen. What do you see as the main benefits of hempcrete as a building material?
ALEX ESCHER Hempcrete is a notable stand-out compared to other organic building materials. It is mold, fire and pest resistant as well as being able to passively regulate the temperature of the building. In other words, hempcrete thermal properties create buildings that are cool in the summer, warm in the winter; naturally maintaining a comfortable living space. This property also doubles as a passive air filter, removing volatile organic compounds from the environment – similar to a house plant.
JASON In your view, how can hempcrete fulfill currently unmet needs or expectations for potential homeowners and developers?
BOB ESCHER Hempcrete is the material the green industry has been waiting for. The construction industry is in a global transition period where green materials and green construction are starting to have mainstream applications. Hempcrete is a low-tech solution for a number of problems plaguing the industry. Its biggest benefit is that it’s carbon negative. That means the material itself sequesters more CO2 during its lifecycle then is emitted during production. A hempcrete wall removes the need for siding, Tyvek, plywood sheathing, insulation and sheet rock . This should be considered when evaluating the true cost of a hempcrete build system. It can also be incorporated into regional aesthetics making it a good product for designers, engineers and homeowners. Elegant in its simplicity, but complex in its utility.
The main limitation right now is the lack of certification from local and national building codes and lack of available research from American institutions. At first, I thought this was a minor issue – since plenty of European data is available. Just convert everything from Celsius to Fahrenheit and you’re done, right? Wrong. Unfortunately, there is quite a bit more to it than that. Hempcrete will not become a viable building product until building codes catch up to the work being done overseas. They are decades ahead of us. That is why we are staying small and focusing on education, infrastructure and proof-of-concept. Progress is starting to come however, so I believe architects and builders need to learn about this subject matter.
“Hempcrete is the material the green industry has been waiting for.”
— Bob Escher
JASON What are your thoughts on hempcrete blocks and panels? Do they have the capacity to meet structural needs, as well as building codes?
ALEX We’re looking at paneling systems, specifically for future high-end residences. One of the benefits there as opposed to making hempcrete on the jobsite is the labor demands right now. Especially with a limited market for skilled labor that exists today. And that’s mainly because it is early in the game. When these sustainable materials become more available and more ubiquitous, this will be a big advantage in that regard. That being said, hempcrete is really viable. It is very easy to work with, and for optimum performance removing as many variables as possible is the way to go.
BOB Some of the Lego-like block systems are a really great way to do this since the blocks that lock together can help create a structure. On the other hand, when you start working with blocks you have many joints. My feeling has always been the fewer joints, the better as far as waterproofing, airflow and infiltration — so I think prefabricated panels is the best way to do this in the future. This way you can have a consistent product with a certified R-value and fire rating.
JASON The AIA encourages hemp insulation as a way of reducing embodied carbon. What needs to happen for the Association and its members to start seeing hempcrete as a viable alternative to traditional building materials — specifically to help meet its 2030 commitment goals?
BOB I think the AIA has taken notice but hasn’t yet started to put it out there to members that there’s this new material. This is why we are designing and building small outbuildings to help educate people what this is all about. I am talking about barns, stables, outbuildings, etc. — nothing commercial. I know that five years from now, it will be totally different. It’s all about education at this point in time. Not only for the average Joe, but for zoning officials, state officials, contractors, architects, engineers — everybody. As of now, collectively speaking, not a lot of people know anything about this topic. Now that the Farm Bill has been enacted, it’s going to start exploding. It is the future.
JASON What can the design-build community be doing locally to speed up the certification and local code enactment process?
BOB Build small. The only way hempcrete is going to move out of the cottage industry is if construction professionals can see its application in real-world environments. The material is incredibly simple to work with — but isn’t foolproof. The focus right now has to be on quality and safety. Building small structures are the best way to demonstrate proof-of-concept and provide key training opportunities. Once this starts happening a lot of the bureaucratic bottlenecks will start to get untangled.
JASON What resources do you recommend for those who want to learn more?
BOB Escher Design provides consulting services for hempcrete projects and there are a number of books online for enthusiasts. Building with Hemp by Steve Allin is a personal favorite — as well as The Hempcrete Book by Alex Sparrow & William Stanwix. If you want something more hands-on I would recommend signing up for a hempcrete workshop. Left Hand Hemp out of Boulder, Colorado does work all over the country and is a good place to start.