High fuel costs and concern for the environment have brought a new urgency to how we insulate our homes. Whether it’s fiberglass, foam board, or reflective barriers to keep cool in hot areas, insulation saves energy by controlling how heat moves in or out of the house and plugs leaks in the house’s “envelope” to prevent cold from coming in. With the rise of spray-foam insulation, it’s easier than ever to insulate with minimum disruption to standing walls.