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Insulating Underground Homes

Insulating underground or earth-sheltered homes is a vital step in the construction process. A lack of the proper amount and type of insulation leads to conditions that can make the home uninhabitable, such as a buildup of mold and mildew.

Insulating an underground home

Waterproofing and improving air quality in an earth-sheltered home go hand in hand with proper insulation. All three factors must be done to meet construction standards.

Underground homes are classified according to their construction. A structure whose topmost feature sits below the surrounding surface is considered a full-fledged underground home. The other two types are very similar to one another. An earth-bermed home is one that has had soil banked around one or more of its walls and possibly over its roof. An in-hill home is built into a hill, with only one of its walls visible outside.

Protection by Reduction ...

Choosing to build an earth-sheltered home has the advantage of reducing the amount of energy required to keep the interior temperature comfortable. It is especially useful in areas where the climate tends to gravitate toward the extremes of hot and cold for reducing heating and cooling costs. From an aesthetics perspective, it blends in with the surrounding terrain. It reduces noise and the house is better protected from bad weather, natural and man-made disasters.

Underground Home Insulation

What the Sheet?

Earth-sheltered homes will usually have either close-celled extruded polystyrene sheets or spray-on foam as insulation. Polystyrene is efficient by itself, utilizing a few layers on the exterior of the structure. For structures that do not follow a standard design, the spray-on foam is the preferred material. However, foam requires an extra material on top of it to protect it from time and weather. In some instances, underground homes may not be insulated at all. For these situations, the soil below the surface is considered efficient enough at retaining the necessary heat.

Sufficient insulation will ensure that the home remains a comfortable temperature throughout the year. Mold and mildew can develop as a complication when the home has not been properly insulated and waterproofed. Insulation helps keep moisture caused by humidity from creating such problems. Otherwise, the air quality of the home is compromised.

Earth Home Insulation Wall

Just Say No to Retrofitting ...

A substantial amount of insulation is worth the extra effort, as are sealants, in waterproofing and insulating the structure because it is difficult and costly to fix any problems with it once the house is completed. Waterproofing material may be placed on both sides of the insulating material when foam is used. Anything that has the potential to leak, including seams, should receive extra attention and insulation. Even with these precautions, cracks and leaks can occur. The interior of the house may still have extra humidity. Using a dehumidifier is a good precaution to take.

Another possibility for insulating an underground structure is to use the insulating material in an umbrella design. It is formed by placing insulating material above the underground roof of the structure. Domed houses present an excellent reason to choose this method. The insulation should be large enough to cover not only the dome, but also extend past the structure on all sides for a few feet to increase the insulated area.


Regardless of what type of material is chosen, insulating underground homes is an important step that should be included in the planning and construction process.


Written by Kevin Knatloa

First Published on November 05, 2012

Updated November 22, 2013