The zeroHouse design attains virtually every goal of green technology by functioning completely off the grid. However, this would be impossible if it weren't for proper insulation. Because of the prefabricated nature of the house, the design needs to be usable in various kinds of weather -- both hot and cold climates. Although the house incorporates highly efficient heating and air conditioning systems, insulation allows those systems to work as little as possible by stopping heat from invading during hot weather and from escaping during cold weather.
Structural insulation consists of closed-cell foam, which, unlike open-cell foam, prevents the flow of vapor in addition to heat. This insulation achieves a thermal resistance rating of R-58 for walls, roof and floor. The thermal resistance rating indicates how well a material stops heat flow. The zeroHouse's insulation rating is impressively high, especially if you compare it to the standard recommended wall insulation ratings that range from about R-11 to R-28 in the U.S. [source: EERE].
Each room has full-wall windows, so it's pretty important that those windows resist heat flow. These full-wall windows are triple-insulated and use low-e heat-mirror glass. "Low-e" refers to low-emissivity and means that the glass incorporates a layer of metallic oxide, which hampers heat transfer. Heat-mirror glass reflects invisible heat without reflecting too much light.
Accounting for every nook-and-cranny, the architect uses high-quality insulation for the doors, as well. The doors are insulated with vacuum-sealed aero-gel panels. Aero-gel is a substance NASA made from the same materials as glass. However aero-gel is far less dense than glass -- in fact, it's the lightest solid on earth [source: Stenger], and it's a very efficient insulation material.
Because of this insulation, the house is suitable in a wide range of climates. The architect claims the house is suitable at latitudes 36 N to 36 S, at any time of the year. However, during the appropriate seasons, you could occupy the house comfortably in latitudes 47 N to 47 S.
The house's plumbing system also is efficient, relying on a force that is available at any time of day, is universally accessible, renewable and incredibly cheap (in fact, it's free). Read about this energy source on the next page.