Consistent, well-installed insulation throughout a house – when combined with a continuous and effective air barrier – keeps you and your house warmer in the winter and cooler in the summer. The effectiveness of any insulation is described in terms of its R-value. The higher the R-value, the lower the heat loss (in winter) or heat gain (in summer). There are many insulation choices to consider. The type and amount of insulation you choose will depend on the particulars of your house and your budget.

Types of Insulation

There are four basic types of insulation: loose fill, batts and blankets, rigid board and spray foam. The most appropriate type of insulation to use will vary based on the type of construction, the extent of the rehabilitation planned and applicable code requirements.

Loose-fill Insulation

Loose-fill insulation includes loose fibers that is blown into building cavities or attics using special equipment. It generally costs less than batt insulation and fills nooks and crannies easier and provides better sound insulation than batt-type insulation.

Batt and Blanket Insulation

Batt and blanket insulation is made of mineral fiber — either processed fiberglass or rock wool — and is used to insulate below floors, above ceilings, and within walls. Generally, batt insulation is the least expensive wall insulation material but requires careful installation for effective performance.

This type of insulation is best suited to a standard joist, rafter, or stud spacing of 16 or 24 inches. Batts and blankets come in widths to fit securely between the wood-framing members. Some come with a radiant barrier backing. Batts generally come in lengths of 4 or 8 feet. Blankets come in long rolls that are cut to the desired length for installation. Both batts and blankets typically have an R-value of approximately R-3 per inch of thickness.

Rigid Board Insulation

Rigid board insulation is commonly made from fiberglass, polystyrene, or polyurethane and comes in a variety of thicknesses with a high insulating value (approximately R-4 to R-8 per inch). This type of insulation is used for reproofing work on flat roofs, on basement walls and as perimeter insulation at concrete slab edges, and in cathedral ceilings.

Spray Foam Insulation

Spray foam insulation is a two-part liquid containing a polymer (such as polyurethane or modified urethane) and a foaming agent. The liquid is sprayed through a nozzle into wall, ceiling, and floor cavities. As it is applied it expands into a solid cellular plastic with millions of tiny air-filled cells that fill every nook and cranny. Spray foam insulation should be applied by a professional using special equipment to meter, mix, and spray into place. Spray foam insulation is commonly used for retrofits; it is good for irregularly shaped areas and around obstructions.

Spray foam materials cost more than traditional batt insulation. However, since spray foam forms both insulation and an air barrier, it can be very cost effective because it both eliminates the steps for air-tightness detailing (such as caulking, applying house wrap and vapor barrier, and taping joints).