Banned for 90 Years, This Building Material Returns With 15x Concrete's Insulation and Centuries of CO₂ Storage

[orangecrush]

The inner core of the hemp stalk consists of a woody substance known as the hurd. When processing facilities separate these hurds from the outer fibers of the plant, the raw material is mixed with hydrated lime and water to initiate a chemical curing process.

A technical analysis published in an NCBI scientific review shows that the lime binder coats the porous hemp hurds, creating a lightweight matrix. Over time, the lime reacts with carbon dioxide in the air, undergoing a carbonation process that gradually converts the binder into calcium carbonate stone.

The resulting composite material provides a thermal insulation capacity that can be up to 15 times greater than standard concrete. This thermal efficiency helps stabilize indoor temperatures by reducing the rate of heat transfer through the exterior walls of a home.

The material also exhibits specific moisture-handling characteristics known as hygroscopic behavior. The open pore structure allows the walls to absorb water vapor from indoor spaces during periods of high humidity and release it when the air becomes dry.
This breathability prevents the accumulation of liquid water inside the wall assembly. By eliminating trapped moisture, the chemical composition of the lime binder maintains a high pH level that naturally resists the growth of mold and deters insect infestations.

https://dailygalaxy.com/2026/05/banned-for-90-years-this-building-material-returns-with-15x-concretes-insulation-and-centuries-of-co%e2%82%82-storage/

[Hugin]

1. Nice!

[maxsolomon]

2. Standard Concrete's insulation R-value is 0.08/inch.

15x R-0.08 is R-1.2/inch.

A standard 6" insulated wood stud wall is R-20.

Maybe focus on another feature of the material?

[TheRickles]

3. Yes, but most of that R-value is from the fiberglass insulation, not from the wood.

Wood R's range from 0.7 to 1.4 (softwood to hardwood), so if hemp studs were used with similar insulation as in your counterexample, the R-value would be similar. And forests don't have to be cut down to produce hemp.

[sl8]

4. But the hempcrete is only being used as insulation, not as structure

Last edited Fri May 22, 2026, 02:34 PM - Edit history (1)

In other words, they're not replacing wooden studs with "hemp studs" (because this hemp material has very little structural strength), they're replacing fiberglass insulation with hempcrete insulation.

In the example shown, the hempcrete is to fill the cavities in a wood framed wall, instead of the typical foam or fiberglas fill, so it makes sense to compare R values of the hempcrete with other insulation materials, not with the insulating qualities of the wood stucture. They specifically point out that the hemp material isn't used structurally, as it lacks the strength of standard concrete.

Likewise,the forest vs. hemp sustainability argument doesn't work. You still need just as much framing material if you use hempcrete for insulation rather than using more common insulation. You could use steel for framing instead of wood, but you could do that with more common insulating materials just as well.

Wikipedia article on hempcrete/hemplime:
https://en.wikipedia.org/wiki/Hempcrete

[TheRickles]

5. Got it - thanks for clarifying.

Though hempcrete doesn't introduce plastics into the environment the way fiberglass or foam insulation does.

[sl8]

6. Good point. nt

[maxsolomon]

7. Not my point.

Why address the R value at all. The renewability and carbon footprint is the selling point.

[SheevaL]

8. Hemp is so much more...

Hemp was a staple product for centuries. Ropes for ships, etc., as food with essential amino acids & omega 3, 6 & 9 fatty acids, bug-resistant & fireproof, flooring in homes, 80% of all textiles, fabrics, clothes, linen, drapes & bed sheets were made from hemp until the 1820s. Hemp is a clean fuel.

It makes for strong paper products; the U.S. gov predicted that by the 40s all paper would come from hemp & that no more trees would need to be cut down; 1 acre of hemp grown (90 days to grow) equals 4.1 acres of trees (15+ yrs to grow).

2,200 years ago, Chinese paper made from hemp was found. 1st printed Bible (Gutenberg) used hemp. Thomas Paine used hemp to print leaflets to spread the idea of American independence. And, the 1st 2 drafts of the American Declaration of Independence were written on Hemp.

21 Apr 2023, UBC students constructed one of Canada’s first ‘carbon-minimal’ hempcrete buildings.

Hemp was/is a farmer's best crop and immensely profitable, which would outweigh the costs of industrial decorticators; co-ops, like those for sugarcane production, can be set up.

However, the U.S.'s 1937 Marijuana Tax Act rendered marijuana & all its by-products illegal, esp hemp, all in support of ensuring DuPont's success with its new product, nylon. DuPont et al have had their day, forcing PFCs/forever chemicals that are crushing the world.

Yes, I'm all for Hemp in all its useful forms!!

[LetMyPeopleVote]

9. Welcome to DU

[hunter]

10. Calcium carbonate stone is heated to make lime. This emits carbon dioxide.

The heat source is usually a fossil fuel which also emits carbon dioxide.

As the lime reacts with carbon dioxide from the air, as the finished product cures, it absorbs only a fraction of the carbon dioxide that was emitted in making it.

Lime is not a "net zero" product. Neither is hemp.

Refurbishing existing structures usually has a smaller environmental impact than new construction. In an ideal world we'd be rebuilding our cities, turning them into attractive affordable places where car ownership is unnecessary -- office space turned into apartments, etc.

The "back to the land" Mother Earth News sort of environmentalism was never good for the environment.

I think the harshest lesson from Chornobyl is that humans going about their ordinary business do more damage to the natural environment than radioactive fallout from the worst possible sort of nuclear power plant accident.

Other than plastics used for decoration or insulation, I think modern construction materials are hard to beat -- concrete, concrete block, wood or metal framing, rockwool, and gypsum board. If concrete structures are allowed to stand for centuries and repurposed over the decades with gypsum board and wood or metal framing the environmental footprint can be smaller than that of structures that are torn completely down and hauled off to the landfill after a few decades use.

Here's another example of hemp (in the form of canvas) being used as a construction material: