When insulating your home, you can choose from many types of insulation. To choose the best type of insulation, you should first determine the following:
- Where you want or need to install/add insulation
- The recommended R-values for areas you want to insulate.
The maximum thermal performance or R-value of insulation is very dependent on proper installation. Homeowners can install some types of insulation — notably blankets and materials that can be poured in place. Other types require professional installation.
When hiring a professional certified installer:
- Obtain written cost estimates from several contractors for the R-value you need, and don’t be surprised if quoted prices for a given R-value installation vary by more than a factor of two.
- Ask contractors about their air-sealing services and costs as well, because it’s a good idea to seal air leaks before installing insulation.
To evaluate blanket installation, you can measure batt thickness and check for gaps between batts as well as between batts and framing. In addition, inspect insulation for a tight fit around building components that penetrate the insulation, such as electrical boxes. To evaluate sprayed or blown-in types of insulation, measure the depth of the insulation and check for gaps in coverage.
LOOSE-FILL AND BLOWN-IN INSULATION
Loose-fill insulation consists of small particles of fiber, foam, or other materials. These small particles form an insulation material that can conform to any space without disturbing structures or finishes. This ability to conform makes loose-fill insulation well suited for retrofits and locations where it would be difficult to install other types of insulation.
The most common types of materials used for loose-fill insulation include cellulose, fiberglass, and mineral (rock or slag) wool. All of these materials are produced using recycled waste materials. Cellulose is primarily made from recycled newsprint. Most fiberglass contains 20% to 30% recycled glass. Mineral wool is usually produced from 75% post-industrial recycled content. The table below compares these three materials.
RADIANT BARRIERS AND REFLECTIVE INSULATION SYSTEMS
Unlike most common insulation systems, which resist conductive and sometimes convective heat flow, radiant barriers and reflective insulation work by reflecting radiant heat away from the living space. Radiant barriers are installed in homes — usually in attics — primarily to reduce summer heat gain, which helps lower cooling costs. Reflective insulation incorporates radiant barriers — typically highly reflective aluminum foils — into insulation systems that can include a variety of backings, such as kraft paper, plastic film, polyethylene bubbles, or cardboard, as well as thermal insulation materials.
Radiant heat travels in a straight line away from any surface and heats anything solid that absorbs its energy. When the sun heats a roof, it’s primarily the sun’s radiant energy that makes the roof hot. A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof. The hot roof material then radiates its gained heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. A radiant barrier reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic. To be effective, it must face an air space.
Radiant barriers are more effective in hot climates, especially when cooling air ducts are located in the attic. Some studies show that radiant barriers can lower cooling costs 5% to 10% when used in a warm, sunny climate. The reduced heat gain may even allow for a smaller air conditioning system. In cool climates, however, it’s usually more cost-effective to install more thermal insulation.
SPRAYED-FOAM AND FOAMED-IN-PLACE INSULATION
Liquid foam insulation materials can be sprayed, foamed-in-place, injected, or poured. Some installations can have twice the R-value per inch of traditional batt insulation, and can fill even the smallest cavities, creating an effective air barrier.
TYPES OF LIQUID FOAM INSULATION
Today, most foam materials use foaming agents that don’t use chlorofluorocarbons (CFCs) or hydrochlorofluorocarbons (HCFCs), which are harmful to the earth’s ozone layer.
Available liquid foam insulation materials include:
- Polyisocyanurate (polyiso)
Some less common types include Icynene foam and Tripolymer foam. Icynene foam can be either sprayed or injected, which makes it the most versatile. It also has good resistance to both air and water intrusion. Tripolymer foam—a water-soluble foam—is injected into wall cavities. It has excellent resistance to fire and air intrusion.
Liquid foam insulation — combined with a foaming agent — can be applied using small spray containers or in larger quantities as a pressure-sprayed (foamed-in-place) product. Both types expand and harden as the mixture cures. They also conform to the shape of the cavity, filling and sealing it thoroughly.
Slow-curing liquid foams are also available. These foams are designed to flow over obstructions before expanding and curing, and they are often used for empty wall cavities in existing buildings. There are also liquid foam materials that can be poured from a container.
Installation of most types of liquid foam insulation requires special equipment and certification and should be done by experienced installers. Following installation, an approved thermal barrier equal in fire resistance to half-inch gypsum board must cover all foam materials. Also, some building codes don’t recognize sprayed foam insulation as a vapor barrier, so installation might require an additional vapor retarder.
Liquid foam insulation products and installation usually cost more than traditional batt insulation. However, liquid foam insulation has higher R-values and forms an air barrier, which can eliminate some of the other costs and tasks associated with weatherizing a home, such as caulking, applying housewrap and vapor barrier, and taping joints. When building a new home, this type of insulation can also help reduce construction time and the number of specialized contractors, which saves money.
BLANKET: BATT AND ROLL INSULATION
Blanket insulation — the most common and widely available type of insulation — comes in the form of batts or rolls. It consists of flexible fibers, most commonly fiberglass. You also can find batts and rolls made from mineral (rock and slag) wool, plastic fibers, and natural fibers, such as cotton and sheep’s wool. Learn more about these insulation materials.
Batts and rolls are available in widths suited to standard spacing of wall studs, attic trusses or rafters, and floor joists. Continuous rolls can be hand-cut and trimmed to fit. They are available with or without facings. Manufacturers often attach a facing (such as kraft paper, foil-kraft paper, or vinyl) to act as a vapor barrier and/or air barrier. Batts with a special flame-resistant facing are available in various widths for basement walls and other places where the insulation will be left exposed. A facing also helps facilitate fastening during installation. However, unfaced batts are a better choice when adding insulation over existing insulation.
Standard fiberglass blankets and batts have a thermal resistance or R-value between R-2.9 and R-3.8 per inch of thickness. High-performance (medium-density and high-density) fiberglass blankets and batts have R-values between R-3.7 and R-4.3 per inch of thickness. See the table below for an overview of these characteristics.