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Insulating Attic Floors

We want to add wooden flooring up in our attic.  Before doing so, we were going to replace the existing installation.  Are we going to encounter any moisture problems with the new attic installation if we cover it with a wooden floor?  Are there any special precautions we should take?

GBarthel 10-21-06

The most common mistake that people make when flooring an insulated attic is “squishing” the insulation.  Attic insulation works because it traps air.  Compress that insulation under a floor and the air gets pressed out, robbing the insulation of it’s efficiency.

In a perfect world, you’d buy insulation just thick enough to fit inside ceiling joists, floor over and be done.  But, here is the kicker.  Most ceiling joists are simply not deep enough to hold the 10” to 15” of insulation required by today’s energy standards.

I suggest you only floor that portion of the attic you absolutely need for storage.  For the rest, install 10"-15” of insulation and let it rise above the thickness of the joists.  Also, be sure to use unfaced fiberglass batts, and make sure you have enough attic ventilation to avoid moisture build-up.

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