This publication is part of the Cold Climate Collection from the Cold Climate Housing Information Center at the University of Minnesota.
Insulation is any material that reduces the rate of heat transfer from one area to another.
During the summer, insulation reduces heat gain and provides a cooler environment. Adding a vapor retarder on the warm side of the wall reduces the movement of water vapor from the inside air through the exterior building materials. Any product with a relatively high resistance to heat flow can be considered an insulator. Insulation Materials Fiberglass and mineral wool, including rock and slag wool, are made with a fibrous form process using rock, slag, or glass. Fiberglass differs from rock wool only in the source from which the fibers are spun.