Left Hand Hemp knows there is a better way to build. Through hempcrete building workshops, we teach how to work with the hemp as a construction material. For this project. community members, students, hemp industry professionals and interested construction groups came together to help build an architecturally rendered, CO2 sequestering and fire-resistant building from “Hempcrete”.
Hempcrete consists of hemp hurd, lime and water.
Here is a quick peak at the timeline:
First, Architect Bob Escher, with Escher Designs in Vermont, and Homeowner Eric McKee came up with the design for the 16 x 20 workshop building.
Next, McKee talked to the city building code office about the properties and benefits of hempcrete and got an approval to build a 16 x 20 workshop space! A concrete pad was laid and in three weeks, we would were ready to begin putting up the structure!
The General Contractor, Timberwight, and Builder, Mark Cover from Forbes Road Sawmill put together the post and beam structure with wood from McKee’s family land in Pennsylvania. Beautiful 8 inch thick hemlock beams were milled and shipped to Denver. With the help of Mark’s right hand man, Onefree Foster, and a crew of ruffians, the post and beam structure was up in just 2 and a half days!
Hempcrete has to be formed into the walls in a similar way that concrete is poured into forms. The main difference is the texture, where concrete is wet, hempcrete has the consistency of moist granola. Forming is always the slowest part of the process with hempcrete. We had an amazing group who were able to more than handle the task of moving, cutting, and attaching the forms as the hempcrete crew was always close behind. Ideally, a homeowner would want to construct a monolithic structure (hempcrete for the walls, the floors, and the ceilings of the building) as to eliminate thermal bridging to the outside.
The simple ratio of hemp hurd, lime and water is used in creating the hempcrete insulation material. In a mortar mixer (not concrete mixer) we mixed together Saint Astier’s Batichanvre, (Hydraulic Lime), from Transmineral, hemp hurd from Ole Dominion Hemp, and water.
We had teams mixing and packing in the forms. The mixing team tested each batch to ensure we reached our desired consistency. Once the batch was ready (about 10 minutes in mixer) it was transported to the building where the ready team of hempsters was anxiously waiting to put it into the forms. When installing the hempcrete, it is best to “hand tamp” with enough pressure to compact it, but not too much as you could diminish the pore space between the hurd pieces. Overtamping with tools and too much force can lessen the R value by reducing the amount of air that is able to be trapped in the material.
Hempcrete replaces fiberglass, drywall, and latex paint.
A natural earthen plaster is the best exterior and interior treatments for hempcrete.