The low cost green homes website contains a lot of information on nine of the lower cost methods of building a green home. There are more factors to consider than the upfront investment such as what the energy bills, maintenance and repair bills will be in the future. The effect on your health is probably most important of all. The green building techniques on the site can cost low to moderately higher than conventional building, but less in the long run.
The main problem with traditional building is energy efficiency with losses at every stud with their R-value of less than 7, attracting condensation, mold and rot. Insulation sags and compresses over time and rodents and insects move in to framed walls. Most of the green built homes are well-insulated and require smaller, cheaper heating and cooling units which may only need to be supplementary if you use passive solar and convective cooling design. The homes last longer requiring less maintenance and fewer repairs. Insurance is cheaper because they are better fire, wind and earthquake risks. They are healthier, more comfortable and better for the planet.
To touch briefly on some of the types:
- The cheapest and easiest to build are pole houses which do not need excavation and use little wood and concrete.
- The superadobe (also called earthbag) homes use free non-toxic locally available material, provide great insulation and stability, and are easy do-it-yourself homes. Long or short sandbags are filled with earth from the building site and stacked or coiled into layers,with barbed wire for mortar and reinforcement. They are then covered with plaster to protect the bags and make unique shapes.
- Straw bales are usually locally available, but the straw must be kept dry especially at the foundation, around doors and windows and at the tops of walls. Plumbing should be run outside the bales and the coating of plaster or stucco must be thorough. Straw will last almost indefinitely if its moisture is kept below 20 percent.
- The R-value of monolithic dome shells is effectively a 60 because of the concrete thermal mass and no air or moisture infiltration, maintaining a more even temperature. Even with only three inch thick concrete, they use less than conventional concrete structures, are extremely fire, earthquake and wind resistant, do not rot, warp or get eaten by pests.
- American Ingenuity (AI) geodesic domes are made with triangle panels supporting each other with no framework. Each panel is quarter inch wall board on the interior, R-28 seven inch expanded polystyrene (EPS) insulation in the middle and half to three-quarter inch steel-reinforced concrete on the exterior. Up to 34 feet in diameter, the panels are temporarily supported with leaned two by four boards. When the panels are in place, an overlapping steel mesh is locked with steel C-rings and seams coated with two layers of concrete mix, then primed and painted. The EPS insulation is both vapor and air barrier against air infiltration, is free of chlorofluorocarbons (CFCs) and formaldehyde, fire, wind, earthquake, mold, mildew and snow load resistant, and not eaten by pests.
- Pumice-Crete® is made of lightweight pumice rock, Portland cement and water poured into forms to create walls in place with a concrete bond beam poured on top of walls for roof connectors and sealed with plaster. With minimum 14 inch walls, no other support is necessary for one or two stories. Pumice-Crete® uses little cement, is a natural material collected in volcanic areas, does not burn, rot or get eaten by pests, is a better insulator with the bubble pockets and can be finished with just stucco for interesting shapes.
- Liteblok, made by Cresco Concrete Products in the Carolinas, LLC, is similar to Pumice-Crete in that the tiny air bubbles make good thermal insulation but keep the concrete strong enough to be an unsupported house wall. Litebloks are interlocking lightweight, easy to handle concrete blocks that need no mortar, are non-toxic, fireproof, earthquake, wind, mold and pest resistant, will not rot or warp and maintain their R-value over time. The exterior can be finished with textured paint or thinset mortar.
- Structured Insulated Panels (SIPs) are two sheets of oriented strand board (OSB), or sometimes fiber cement board or plywood, glued around a layer of expanded polystyrene (EPS) and serving as structure and insulation with no framing for walls or roofs needed. They cut energy bills in half because of reduced air infiltration and superior insulation. They are precision-made in factories with little waste, are quicker to put up than stick-building, burn slower than stick houses with no off-gassing and are faster to wire because they come with electrical chases for plugs and switches.
- RASTRA panels, a Composite Insulating Concrete Form (ICF), are 85 percent recycled expanded polystyrene (EPS) and 15 percent cement. They are lightweight with R-values up to 48. Rebar and concrete are inserted in channels in the panels to form strong gridwork, horizontally or vertically. They are quick to assemble, do not rot, wick or hold moisture, are seven times better in earthquakes than wood structures, fire resistant, do not warp, expand and contract, or get eaten by pests.
Read more detailed information on each type of low cost green home on the website and the local Greenville S.C. green materials and services article for local businesses who can help with these types of homes. Other area contacts are Insulated concrete forms, ICF Constructors Inc; Natural building straw bale, earthbag, cob homes, MudStrawLove; Kleiwerks International and Clarke Snell.