Hempcrete and kenaf crete use plants with a lot of fiber, along with lime, to create blocks or fill that have many qualities of concrete but is much more renewable and ecologically friendly.
One of the nation’s first hempcrete homes, Asheville.
Hempcrete fills the walls.
Hempcrete makes excellent environmentally friendly insulation and has many applications in building outside of walls for houses.
Hemp has been used as a building material since Roman times. Hemp housing from the Middle Ages is still around. In Florida, these approaches are very attractive from a number of angles. The fact that hempcrete regulates humidity and is water and mold resistant is a big plus in humid environments.
Blocks of hemp.
Kenafcrete is much less well known than hempcrete and thus, much less well studied. Kenaf has many of the same fiber and other useful properties as hemp (same plant family) but is legal to grow anywhere in the US without a permit.
Aircrete uses a machine to inject air into an ecologically friendly cement mixture to create strong but very light building materials by pouring it into molds. This is a relatively new building method that is quite beautiful and has many positive qualities.
I hope you can see just how beautiful non-polluting buildings can be. There are many approaches to “green” building today but most include much more pollution, mined materials, and embodied energy than natural buildings. Green building is still vastly superior to conventional modern approaches however. If you’re going to build, it’s worth it to explore all of your options!
For pro's and con's we will only cover hempcrete.
Pros (for hempcrete):
Can be used similar to concrete, something builders are familiar with.
Can be carbon negative, depending on the process, because hemp sequesters a lot of carbon. Is fire and earthquake resistant.
Combines insulation with thermal mass.
Hemp can be grown in a few months, and is very renewable.
Regulates humidity (absorbs it when air is moist, releases it when less moist) Doesn’t degrade when kept off the ground, but can be composted or used as mulch at end of life. Good acoustics and cuts sound well.
Resists mold.
Lasts 100’s of years.
Cons (for hempcrete):
Limestone (an ingredient in hempcrete) is mined to create lime concrete.
Long curing times, not as good at load bearing as concrete (but excellent when combined with other things - for instance, bamboo). Load bearing methods of production continue to be explored.
Can be harmed by repeated water exposure. Must not touch the ground or be earth bermed or remain wet.
If monocropped, hemp can deplete soils and create problems that any monocrop creates.