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.