HouseChalk
Fiberglass insulation
Fiberglass insulation is insulation made from fine glass fibers, available as batts, rolls, or loose-fill.
Why it matters
It is affordable and widely available. It does not absorb water easily, but it does not stop air movement. Air sealing is still needed.
Where people get this wrong
Fiberglass does not stop air leaks. Air can blow right through it. That is why air sealing the building envelope matters even when walls are full of insulation.
Real-world example
You feel a draft near an outlet on an exterior wall even though the wall is full of fiberglass batts. The insulation is there, but air is leaking through gaps.
Where this hits your build
This affects comfort, energy costs, and indoor air quality. It gets locked behind drywall, so decisions here need to be right before finishing starts.
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