Fiberglass insulation

Air-permeable insulation whose performance depends strongly on installation and air control.

What changes first

Look for dirty air-wash marks, compression and wet facings. The pattern and location usually matter more than color alone.

Moisture and movement behavior

Record whether the material changes after rain, water use, heating cycles or seasonal humidity. A material can display the damage while the source is somewhere else.

Before repair

Determine whether the material is the source, a pathway or only the final surface. Correct the controlling condition before replacing finishes.