Hempcrete Gets A Boost In US Residential Building Code

Whenever I write about alternative building materials, a commenter will ask, "What about hemp?" The main reason I don't cover the hemp scene is because it encourages the hippie aesthetic we want to avoid. More importantly, it's not easy to find or use in the United States

But in October 2022, hemp concrete was added as an addition to the US Residence Code, which is used in 49 of the 50 states, and will be included in the 2024 International Residence Code (IRC) . According to the permit, "the council believes that this is yet another technology similar to the straw and grain wall construction industry to be codified as an additional alternative method to be codified with uniform requirements to provide safe construction [where the architect or designer has to convince building officials that this is normal.] The building department will make it easier to revise plans to allow for that option."

Here's an example wall from the Code app:

While many sources say hemp concrete is approved for US residential building codes, Chris Magwood, construction expert at Builders for Climate Action, told TreeHagger that being in the app isn't actually in the code.

"Plugin approval is voluntary even after new code is approved. So there will be a lot of places where it won't be a live code enabler for a long time," said Magwood. “It's good if the material is certified, if not fully adopting the code. Often, code officials are exempt from additions like this because it gives them confidence that it has been reviewed by experts and the regulations give them something to plan for. Effectiveness has to be measured, that's what they see. So it's a big step."

Foam concrete is a very interesting material. In The Benefits of Building Homes with Hemp Concrete, Jim Gunshinan of TreeHgger describes it as an "energy efficient, low impact, and water smart building material" that provides a lower carbon footprint than other home building materials. .

But it's so much more than that. It is one of the elements that author Bruce King describes in New Carbon Architecture as "building from the sky," or capturing carbon from carbon dioxide in the air, sunlight, and water, transforming it through the process of photosynthesis. Plants that we can turn into building materials.

"All of these new technologies and more follow a growing awareness that the so-called carbon contained in building materials is far more important than anyone thinks in the fight to stop and reverse climate change. The built environment can go from a problem to a solution."

It is not a structural material in itself, it acts as a solid filler. The Endeavor Center's Free Encyclopedia explains:

“The flax plant bitter is the woody core that remains after the fiber has been removed. This mass is covered with easily wetted (and sometimes hydraulic) lime and water, and the resulting mixture is placed in the wall formwork. The top form can be moved up the wall when hemp concrete is added. The material stabilizes on the wall immediately after solidification. The finished insulation is left exposed to dry on both sides of the wall. Concrete logs provide a compact and uniform surface and are an ideal substrate for plaster. Foil fencing and the more common cladding and wall coverings can also be used."

It takes a long time to dry, up to a week per inch of thickness, and insulation factors vary widely depending on the degree of compaction, as new building codes add:

The 2.1-inch R-value isn't great; Fiberglass belts are rated 3.1 to 3.4. But it has other benefits: it manages humidity well and is mildew resistant. Many builders assume that the actual R-value is higher because of its thermal mass, but the Endeavor Center notes, "While it is true that the thermal performance of a site may differ from the rated R-value, the same is true for any insulation/wall system. Thermal resistance is not can be increased by thermal mass."

Hemp is a low-impact crop, and most importantly for Treehugger, hemp sequesters about 325 kilograms of carbon per metric ton, according to the Carbon Smart Material Palette. However, there are questions about the total carbon content due to the lime that holds it together.

Varnished walls are often plastered, but in the hands of a good architect they are both exposed and beautiful. British architect Paloma Gormley on display at Margent Farm. In his recent book Materials Reform, Gormley writes about how natural materials such as hemp are useful for carbon storage and regeneration design:

“If you build using a variety of materials based on petrochemical compounds, glue, masking tape, glass, concrete and steel, those materials have little or no chance of getting back into the ecosystem in a way that allows regeneration. On the other hand, buildings made from bio-based materials survive time in an entirely different way: the goal is to keep most of the materials of the carbon cycle for as long or longer than they need to be regenerated. In their living world.

Marijuana is still difficult to obtain in the United States, even though it is now legal to grow it. However, it can be imported from Canada and Europe. And now that it has established building codes, it may become even more popular.

But Magwood is not sure aerated concrete will be used in residential areas. "I don't think aerated concrete will play as big a part in the housing market. Being a composite material using a lime-based binder means it has less insulation and is more expensive than other options," said Magwood. on site or in a prefab or unit. Cold climates require at least 12 inches of wall thickness to meet base code minimum requirements, and achieving high performance levels means 16 inches or more, so builders need more materials, which are already more expensive."

"I see that hemp concrete slabs can play an important role in commercial construction, where the material's excellent fire performance (an advantage of limestone cladding) can provide a biogenic carbon storage option for large buildings that are not experiencing fire performance problems. Dry'. biogenic insulation ," added Magwood "I see great potential for aerated concrete sheet materials such as http://calmura.ca/ in both residential and commercial construction. It could be an excellent alternative to plywood/OSB for cladding and sound and fire insulation in building interiors that require additional fire protection. It's a great way to cover hardwood pieces."

Magwood has really tempered my enthusiastic vision of hemp concrete, making every building a regenerative, bio-based, carbon-efficient structure that helps mitigate climate change, but it's a step in the right direction. In his article, Carbon Sequestration in Buildings, Vermont builder S. McCarlton writes:

"It is entirely possible to design, build, repair and maintain high-performance, energy-efficient and sustainable buildings not only with low- or zero-carbon materials, but also with materials that sequester or store carbon, giving buildings a net positive carbon footprint. We buildings then will be part of a global CO2 abatement project, they will be a tool, they will be a CO2 sink and helping to reduce and reverse the effects of climate change.'

Aerated concrete is one material that can help restore carbon-efficient buildings. So tell your farmers to grow hemp now! We may need a lot in 2024.

Hemp concrete panels!