Wednesday, June 12, 2013

concrete vs. hempcrete

Concrete (made of cement, rock, sand and water) is the most widely used manmade material in the world, and the second most used product on the planet, after water. More than a cubic yard of concrete is produced for every person on the planet, per year, and 900 kg of CO2 are emitted for the fabrication of every ton of cement (making a ton of cement results in the emission of roughly a ton of CO2 - and in some cases much more). Almost half of concrete made is produced in China. Cement, commonly composed of calcium silicates, requires heating limestone and other ingredients to 2,640 degrees F (1,450° C). That’s done by burning fossil fuels; it’s the 3rd largest source of greenhouse gas pollution in the U.S. (after electricity production and transportation), according to the U.S. Environmental Protection Agency. Carbonation, not the bubbles in soft-drinks but a process of carbon absorption concrete participates in, could help fight global warming, a bit, but cement and concrete limit ground absorption of precipitation, raise ambient temperature, reduce plant growth, and stifle life in the underlying soil and general vicinity. Hemp-crete, a versatile building material, can be used for wall insulation, flooring, walls and roofing. Used above ground, it’s fire-proof, water-proof, rot-proof and termite resistant. Hempcrete houses need little cooling or heating to stay comfortable, and thus save lots of energy. A lightweight cement-like material weighing but a 7th of what concrete does, hemp-crete has positive acoustic properties (absorbing sound), buffers both temperature and humidity, prevents mould growth, makes the insides of buildings not only comfortable and healthy, but low-maintenance. It forms a hard wall surface yet is vapor permeable and so helps reduce humidity. It not only prevents condensation, but is cost saving through power conservation. It’s 3 times more resistant to cracking from earthquakes than regular concrete. It’s an insulating infill between the frame members rather than a structural element (all loads are carried by internal framing, wood stud framing being the most common), but tends to reduce racking.