Insulation Forum

[Rich]

I will be starting a few topics on different areas of insulation..i.e. wall, foundations, etc. This will be an attempt to get a bunch of different methods for doing this - then eventually wading through the bs and coming up with a method or 2 that work in different climates.

[dhill]

I'm glad you added this, Rich. Insulation is an often taken-for-granted aspect of building. I've learned that hvac guys tend to understand insulation properties fairly well. With energy prices soaring, it'll be nice to get some advice on saving a few bucks with proper insulation.

[Rich]

My biggest question starts with the discrepancies between different "authorities" ideas. For instance, basement insulation.. one says vapor barrier the other says no vapor barrier.
I'm going to add a topic on basement insulation - maybe tomorrow I'll post a couple different methods and we can get into it.

[danh]

Can we also focus on the fact that insulation creates condensation conditions, so that people will stop just arbitrarily insulating whatever they want?

Slapping insulation into any old space is the easiest way to wreck your house.

[pi71]

insulation can wreck your house?

[danh]

insulation can wreck your house?
YES

[Rich]

danh - go a little further in explaining how insulation can damage. IMO it's more than just the insulation - it's insulation combined with incorrect vapor barriers, materials, etc.

[dhill]

This has made me remember a statement my neighbor said when I told him I was going to blow 15" of cellulose in my ceiling. He said that cellulose would collect moisture from humidity and settle and become heavy and crack the sheetrock that's supporting it. Is that a valid point? Are attic batts better than blown cellulose?

[danh]

Many surfaces in a building assembly are kept warm by interior heat.

These surfaces are exposed to interior humidity levels (real humidity, not relative humidity), which are much higher than outdoor humidity levels.

As long as the building assembly surfaces are kept warm, they are not susceptible to freeze thaw damage when wet, nor will any interior humidity condense on their interior surfaces.



Placing insulation between any object & the interior of the building cuts the amount of heat available to that surface. If wet, that surface is now susceptible to freeze thaw damage during the winter.

Since insulation is not an air barrier or a vapor barrier, it does not prevent interior humidity from reaching the exterior surfaces that are now cut off from interior heat. These surfaces become prime locations for condensation & mold.



Additionally, insulation increases how quickly a house can be cooled, that is, it shortens the time it takes to satisfy the thermostat. But air conditioners can't really dehumidify air that doesn't pass over the cooling coil. So in retrofit situations, adding insulation eliminates an air conditioner's ability to dehumidify a house.