Click on [ Example in Survey ] to see a house that has used one, or more, of these sustainable techniques. Please note, this example may be only one of the houses that have used a specific T&P—browse the All Houses in Survey page to find more.
Insulation: Insulation is a primary factor in building a sustainable house. Except for building a smaller house, and constructing it properly for the optimal solar gain, great insulation may be the most important thing that you can do to create a comfortable and sustainable house. There are many types of insulation, and there are two systems for measuring its effectiveness: static R-value, and dynamic R-value aka "Whole wall R-value". The greater the R-value the more effective the insulation. Below are a few static R-values for some common insulations (from: Wikipedia).
Type of Insulation
R-Value Range (per inch)
Fiberglass Batts
Extruded Polystyrene
Polyisocyanate Spray
There are several important things to consider:

• R-value is measured per inch of thickness, so that strawbale, which is typically used in an 18"–22" thickness, has a true R-value of ca. 30; while fiberglass batts, for a 5.5" wall (2x6) has a value of ca. 18.
• There are likely to be gaps between studs/rafters/electrical boxes/etc., and the batts or sheets of insulation, which will reduce the true R-value. Make sure to fill gaps to prevent air penetration. Sprayed on insulation, like polyisocyanate or cellulose, largely eliminates this problem.
• Most insulation works only on conductive and convective heat loss/gain, it does not resist loss/gain from radiation. A separate radiation barrier may be needed, typically an aluminized fabric, but certain types of construction should not have a barrier: strawbale is an example, where breathability is important, and a radiation barrier would reduce, or prevent breathability.
• You should consider the ecological, and health issues associated with any type of insulation. For example, gasses used to create plastic foams should not be greenhouse gasses. Plastics are from petrochemicals—do you really need to use them when other materials are available (like blown in cellulose which is recycled paper, or soy based foams). Fiberglass can cause lung damage, and plastics and adhesives can off-gas toxic fumes (there are new adhesives that are a lot less toxic now on the market, see ).
• Look into Dynamic R-value, it will give you a better understanding of the true insulating value of a wall. Click below to download a copy of a paper discussing dynamic-R from Oak Ridge National Laboratory.
[ download .pdf 280KB ]

Earth-berm, earth shelter, green roof...why not use the free insulating value of earth?!!!