Building a Hemp House
Hemp-building products may soon go mainstream. Here’s why your next home should be made with pot.
June 09, 2014 By: John Riha for HouseLogic
Building a Hemp House is interesting for a lot of different reasons!
No, you can’t saw off a chunk and smoke it.
But if you live in a house made with hemp building products, you may trim your utility bills, have more leisure time, and be safer and more comfortable.
Industrial hemp, the non-stoney relative of its more famous cousin, marijuana, is making its way into the building products marketplace. A recently signed federal farm bill has made hemp cultivation legal again. That means research can kick into high gear — likely leading to new hemp products for siding, roofing, drywall, and flooring. What’s So Great About Hemp? Hemp products — from insulation to particleboard — are non-toxic and resistant to mildew, pests, and fire, making them good choices for green home construction and remodeling. Plus, they don’t cast off any VOCs. Several U.S. states have homes with hemp products, but most are in Australia, Europe, and New Zealand. Why is it green?
- It’s a fast-growing, drought-tolerant plant.
- It doesn’t require chemical fertilizers, which also makes it cheaper to farm.
- Its generous yields could ease pressure on dwindling forest resources.
What Products Are Available Now Previously hemp was illegal to farm here, but legal to import from other countries. That hiked up the price of what would otherwise be a relatively inexpensive material. Those prices should come down as domestic products move into the marketplace. Currently available: Hempcrete: Generic term for a concrete-like material made from imported hemp fibers mixed with lime.
- Can be made into walls or blocks
- Good insulator
- Flexes, so it might be a good material to withstand earthquakes
Cost: A 33-lb. bag is $30 and makes about 5 cubic feet of wall (about 5 sq. ft. of surface area for a 12-inch-thick hempcrete wall) with an insulating factor of R-25 — higher than a regular 3.5-inch stud wall insulated with fiberglass (R-13).
Hemp board: Generic term for material that can be used in place of plywood and particleboard for wall sheathing and green cabinet construction. Cost: 4-foot-by-8-foot sheet of half-inch-thick hemp board, $40; regular particleboard, $20 Hemp Shield: Brand name for an exterior finish for wood decks, siding, planters, fences, and play structures. In professional independent testing, Hemp Shield outperformed other well-known wood finish products. Cost: $41/gallon, which covers about 450 sq. ft.; tinted versions are $45/gallon Hemp insulation: Soft, woven material made from hemp fibers.
- Comparable performance to fiberglass insulation, according to Energy.gov
- Insulating value of R-13 (same as fiberglass)
- Doesn’t release fibers that can get into your lungs
Cost: About $2.75/sq. ft.; fiberglass batts of comparable thickness and insulating value are only about 30 cents/sq. ft
See this great video about building a hemp house in Asheville: Hemp House in Asheville NC
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