By Pat Rasmusssen, Senior Hemp Tiny Homes,
Since the 2018 Farm Bill legalized the growing of industrial hemp, US-grown hemp building materials have come on the market, offering zero carbon, carbon negative, and embedded carbon building options, perfect for home builders using Passive House, Living Building Challenge or even for traditional stick frame construction.
As an agricultural product, the hemp plant captures carbon from the atmosphere as it grows. Building materials made from hemp have a negative carbon footprint because they “sequester” or lock carbon into the material. As a result, they can contribute to a very low, zero, or even negative carbon footprint in buildings.
Hempcrete is a carbon cured insulation product. A composite material mixed on site and used to infill wall cavities, it consists of lime and hemp hurds (the fibrous center of the plant’s stem). As it cures, 7 pounds of CO2 are stored per cubic foot. One ton of harvested hemp fiber sequesters 1.62 tons of CO2; 90% is from cultivation of the plant itself. An acre can offset 9.8 tons of CO2. The hemp crop is harvested after only 120 days, sequestering five times more CO2 than wood. Hempcrete is fireproof.
A new product on the market, hemp insulation is a superior alternative to traditional batts, mineral wool or foam. It comes in sheets 3 ½ inches thick for 2×4 framing with an R value of 13 for 5 ½ inches thick for 2×6 framing with an R value of 20. It is energy efficient to produce: An insulation R value of 10 requires 3.4 kwh of energy for hemp compared to 5.5 kwh for cellulose, 15.6 kwh for mineral wool and 48.4 kwh for polyurethane (fourteen times more energy to achieve the same thermal performance). Hemp is vapor permeable, helping to regulate indoor climate and relative humidity. It is non-toxic, reduces sound transmission and is very resistant to pests.
In a May 28 Webinar “Carbon Negative and Non Toxic Hemp Insulation,” NWEBG builders will have the opportunity to learn from Hempitecture’s Mattie Mead as he explains how and why to incorporate hemp building materials into green building projects. Through an overview of hempcrete and their proprietary HempWool insulation, he will discuss how to create high-performing non-toxic building envelopes that can function as carbon sinks while providing long lasting insulation.
Mattie Mead, founder and CEO of Hempitecture in Sun Valley, Idaho, was inspired to specialize in building with hemp by the mission of Architecture 2030. Since graduating in Architecture, Mead has worked with architects, engineers and developers to bring low carbon designs to life. Hempitecture offers Hempcrete Contractor Trainings, hemp building materials such as hemp hurd and binder, HempWool insulation and tools for hempcrete construction. They built the Highland Hemp House in Bellingham.
Hemp is the new oak! Another product, HempWood is 20% harder than oak and grows 100 times as fast. Compressed hemp pulp fibers are held together with protein based bonding agents. Hemp fiber strands are pressed into logs, then cut into boards that can become blocks, dimensional lumber, flooring, cabinets and tables. HempWood boards are cheaper than oak. Fibonacci’s owner Greg Wilson was a pioneer in making bamboo flooring in China for fifteen years before hemp became legal here, enabling him to open a HempWood factory in Kentucky using American grown hemp.
HempBoard, yet another product, is an MDF sheet product, 4’x8’, in thicknesses of ½ “ or ¾ “, made from hemp with a non-formaldehyde binder in 29 or 39 pound density. It is used for walls, cabinets, flooring, molding and doors. Made in the Pacific Northwest with American grown hemp, HempBoard can be ordered through Bulk Hemp Warehouse.
Hemp products are here, but they have a long road to travel before becoming widely accepted in green building and standard building projects. Economies of scale, distribution networks and lack of industry awareness all present barriers to entry for early adopters. Yet for those ready to try something new, or to build a climate-friendly home, their willingness to step into this bold new class of materials could help lead to broad acceptance within a few years.