The walls in our house will be around 18 inches thick and will be filled with many layers of bat insulation. Our walls could be thinner if we used another type of insulation but other types are expensive. Fiberglass bat insulation will be able to do the job at much less cost. (On a side note, if you read further on the blog, we did up using blown in fiberglass. It ended to be cheeper because the labor to put in three layers of bats was more than the blown in.)
The outside walls hold up the roof and the inside walls hold up the ceiling. This way there is no bridging. Bridging is when the outside wall is in contact with the inside wall through the studs that join them together. “Bridging” draws outside air and moisture inside the wall, and then into the house. In a passive house the thick insulation in between the disconnected walls makes it impossible to draw heat or cold and moisture from the outside.
http://www.finehomebuilding.com/pages/thermal-bridging/
The same will happen with our floors: we will have a mini basement (to house pipes, air-ducts, and the “mechanical” equipment for the home), and it will be insulated. The foundation has three layers: first a layer of gravel, then a layer of rigid foam board, and lastly the cement, or “rat slab” that will form the basement. The layer of foam board acts as the insulation.
This is why a passive house doesn’t need a traditional heating and cooling system: it is very tight with lots of insulation and no bridging.
Be Blue - Protect our sky - Take advantage of federal and/or state tax credits by insulating your home.
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