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New England Builder Sees Huge Potential for Carbon Capture in Hemp Houses

HempStone’s Tom Rossmassler
Tom Rossmassler is the CEO -- Chief Embodied Officer -- of HempStone, based in Northampton, Massachusetts.

Hemp Business

New England Builder Sees Huge Potential for Carbon Capture in Hemp Houses

HempStone’s Tom Rossmassler is passionate about addressing embodied carbon in home construction. He spoke to Let’s Talk Hemp from Northampton, Massachusetts.

How did your career lead you to hemp? 
I’ve been involved with building and construction since the early ‘90s and have always tried to steer clients to local and natural products. I didn’t know about embodied carbon when I started, but I was interested in natural building practices. When I moved outside Boston and was working as an appraiser and doing some real estate transactions, I became involved with the Northeast Sustainable Energy Association and started to learn more about reducing operational carbon in buildings.

I learned about Energy Star and then LEED certification for homes and started a worker cooperative focused on building performance. That company, Energia, was part of the first Living Building challenge for the regenerative built environment on the East Coast. 

My introduction to hemp was back in 1997, when my brother, who was an environmentalist, had us all wear hemp vests in his wedding. 

In 2015 I did an MBA on sustainability and learned more about hemp and using it in building. My capstone project was a business plan to create a hemp processing facility in New England. 

Then, on a trip to Europe, I found the International Hemp Building Association. I learned there about the hemp side of the built environment. I was in Italy with this incredible group of pioneers — people from all over the world — who talked about the need to prove the material is viable from a building science perspective and wanted to highlight projects for a wider audience and develop the industry. 

The trend in the certification world was moving toward health and addressing embodied carbon. I founded HempStone in 2018 to focus on embodied carbon in buildings. [Embodied carbon refers to the greenhouse gas emissions that result from the manufacturing, transportation, installation, maintenance and disposal of building materials.]

What is your role at HempStone?
I am the Chief Embodied Officer, which is a play on the CEO title.  

I am a jack of all trades at HempStone. The challenge is to create a viable business model to keep us going.

Right now, for building projects we focus on installations in a four- to five-hour radius from Northampton, Massachusetts. 

Because of the novel nature of the wall assembly and where the roof intersects with many aspects of the building, we do a lot of consulting and advising. We offer help with design details and work with engineers and architects on how to design with hemp lime and where and how to source other materials, such as specialized tapes.

We spend a lot of time on education now as well. We have taught at Rhode Island School of Design and University of Massachusetts and the Yestermorrow Design/Build School in Vermont. I want to inspire the next generation. We also recruit at our workshops for people who are interested in working on projects.

What is the top priority for building the U.S. supply chain for hemp building?
We need to figure out the future by conducting a lot of R&D. We have worked on R value testing with UMass and are planning to work with them to conduct compressive and other structural testing. Hempcrete, among all carbon-storing materials, has the most ability to scale for impact. The industry needs to be an agent for change to heal our planet from carbon and global warming.

Also, we need to focus on education for literally everybody in the building industry: logistics and supply chain professionals, builders, regulators, building inspectors, architects and engineers.

The green building industry did not embrace embodied carbon until the past few years. Hemp building is a niche within a niche — hemp is a star for embodied carbon. Historically, natural building had been marginalized and not taken seriously in the building industry. We have to overcome that with tools like Chris Magwood’s BEAM calculator, building code adoption and ASTM testing. We need strong evidence for hemp building materials. We need to speak the language of architects and engineers to be taken seriously.

What projects are you working on now?
This spring we are finishing the plaster on two house projects we built last year in Massachusetts and Vermont. 

Coming up, we will be building houses in Maine, New York and Martha’s Vineyard. 

We have also been working a lot with native communities in Alabama, Maine, New York and Minnesota. We consult and train on how to do a building project and also on how to create vertically integrated hemp operations to grow, process and build housing in their own communities.

What are your goals for the rest of 2023? 
We are developing a block product that is going to act as both a retrofit solution as well as a permanent form for spay and cast projects. It will allow people who are not skilled at plastering to finish off a hempcrete project themselves. It’s in beta testing and we are hoping to have that later this summer.

We are also working on a panelized concept. We are constantly looking at materiality and composites for optimization of materials and mixes because not all parts of the country have the same resources. We are researching how people can put projects together without getting hemp hurd and binders from far away. 

I believe this industry needs to grow through collaboration. In other industries, people are protective of their territory. To grow this one we need to share information and work together. We want to scale up without selling out.

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