Attic HVAC Insulation Solutions

Attic HVAC Insulation

• HVAC ducts form a system that runs throughout your house and supplies conditioned air that heats or cools your living spaces. These ducts also return air to the home’s comfort system for re-conditioning. When HVAC ducts are installed in attics, which are unconditioned spaces, they need to be insulated. This reduces unnecessary heating and cooling of unoccupied attic spaces, plus the unnecessary expense to do so. Duct insulation also eliminates “sweating,” or condensation buildup, which encourages mold growth.

Problems

• Inadequately insulated HVAC ducts in attics and other unconditioned spaces can lose up to 30 percent of the heating or cooling energy of your home, according to the U.S. Department of Energy. This happens because thin sheet-metal ducts conduct heat poorly. If ducts are also inadequately sealed, joints leak air and add to energy losses. In summer, cool air escapes from ducts into hot attics and in winter, warm air escapes from ducts into cold attics. Either way, a home’s HVAC system works harder to keep occupied spaces comfortable.

Solutions

• Ducts need to be sealed properly before insulating them. The Lawrence Berkeley National Laboratory’s research shows that duct tape is the worst material to use for sealing ducts. Mastics are recommended, according to the California Energy Commission. They are sticky substances that are painted around duct joints. As the compound dries, it hardens and seals the ducts. Depending on climate, the U.S. Department of Energy recommends different insulation R-values in warm, cold and mixed regions. For people living in warmer climates, such as Florida, California and the southern states, attic R-values should be between R-4 and R-8. In colder climates, such as New England and western mountainous areas, R-values should be between R-6 and R-11. In mixed, or temperate regions, R-values should be between R-4 and R-8.

Materials

• Unlike blown insulation and rolled insulation that are used for ceilings, floors and walls, rigid fiber board insulation is used for HVAC ducts. The inside layer of rigid fiber board is made of fiberglass or mineral wool, and the outside layer is made of reinforced aluminum, which provides a barrier to air and water. Fiber board is usually installed inside HVAC ducts by a professional contractor. When fiber board is applied to the outsides of ducts, it’s secured by pins or clips.