Waterproofing can be a challenge in earth-sheltered construction. Keep in mind these three ways to reduce the risk of water damage in your house: choose the site carefully, plan the drainage both at and below the surface of the house, and waterproof your house.
There are several waterproofing systems currently in use, including rubberized asphalt, plastic and vulcanized sheets, liquid polyurethanes, and bentonite. Each has its advantages and the one you choose will depend on your site and house plan.
Humidity levels may increase in earth-sheltered houses during the summer, which can cause condensation on the interior walls. Installing insulation on the outside of the walls will prevent the walls from cooling down to earth temperature; however, it also reduces the summer cooling effect of the walls, which may be viewed as an advantage in hot temperatures. Mechanical air conditioning or a dehumidifier is often necessary to solve the humidity issue. Proper ventilation of closets and other closed spaces should keep the humidity from becoming a problem in those areas.
Although insulation in an underground building does not need to be as thick as that in a conventional house, it is necessary to make an earthen house comfortable. Insulation is usually placed on the exterior of the house after applying the waterproofing material, so the heat generated, collected, and absorbed within the earth-sheltered envelope is retained inside the building’s interior. If insulating outside the wall, a protective layer of board should be added to keep the insulation from contacting the earth. Depending on the type of structure—wood, masonry, concrete, or steel—insulation may instead be placed inside the walls before the waterproofing material is applied.
Adequate air exchange must be carefully planned when building an earth-sheltered dwelling. Generally, well-planned, natural ventilation or ventilation by exhaust fans can dissipate ordinary odors. Any combustion appliances that are installed should be “sealed combustion units,” which have their own, direct source of outside air for combustion, and the combustion gases are directly vented to the outside. In addition, indoor pollutants emitted by formaldehyde foam insulation, plywood, and some fabrics can accumulate and become an irritant if ventilation is not properly planned.
If you are looking for a home with many energy efficient features that will provide a comfortable, tranquil, weather-resistant atmosphere, an earth-sheltered home could be right for you. With the general information in this publication and more details available from the sources listed below, you are on your way to owning a home that can protect you from the elements and the rising costs of energy and building resources.
– National Renewable Energy Laboratory, United States Department of Energy, Feburary 1997