The Colorado-based Formworks Building Inc. has been specializing in earth sheltered building technology since 1979. The main idea behind their buildings is the creation of sustainable, affordable housing. Formworks structures have an estimated usable life span of over one hundred years without any major maintenance. These houses are built into the earth surrounding the building site, which has the added bonus of protecting the home from raging storms, tornadoes, hurricanes, fires, mudslides and so on.
Houses that are built partially into the earth allow for numerous energy saving features. For example the natural vegetation surrounding the structure forms a natural barrier to protect from extreme temperatures, since the dirt and grass keep heat out in the summer and provide extra insulation during the winter. Grass and other vegetation can also act as a barrier to prevent mudslide damage. The Formworks building system is made up of four components, namely structural steel, shotcrete, water proofing, and installing whole house ventilation and heat exchanger systems.
The building process of a Formworks house begins with the primary structural steel components being lifted into place manually or by lifts, and then bolted together. After the steel beams are in place, the rebar is installed using the rebar receivers already welded into place on the outer flange of the steel. By continuing the rebar from tab to tab around the entire structure the wire frame of the house is created. After this part of the process is completed, a Styrofoam liner is attached to the interior steel of the structure and functions as both form and backstop for the shotcrete.
Shotcrete is pneumatically placed concrete sprayed under pressure through a hose and delivered through a nozzle, and it is applied from the exterior. The Styrofoam is removed from the interior of the house once the shotcrete has set, and is then finished with a thin coat of plaster. The rest of the needed work is standard and can be done by sub-contractors (framing, electrical, plumbing, finish work).
Formworks houses also use a multi component waterproofing system (Polysecure4), which can be applied by the homeowner, laborers or any contractor. First a drain fabric is installed over the top of the waterproofing material and serves to remove hydrostatic pressure and wick any water directly to the footer drains. The Styrofoam is used over the top of the waterproofing system to provide backfill protection, while it continues to provide insulation.
Formworks houses also come with a whole house ventilation and heat exchanger system. This system depends on the exhausted stale air and the fresh ventilation air passing through multiple air passages separated by a composite resin partition plate. This system allows for a transfer of heat from the warm to the cool air stream, while latent energy, namely water vapor transfers from the wetter to the drier air stream. In this way, the fresh air coming in from the outside is automatically pre-heated in the winter and pre-cooled in the summer.