The maximum thermal performance or R-value of insulation is very dependent on proper installation. Homeowners can install some types of insulation -- notably blankets, boards, and materials that can be poured in place. (Liquid foam insulation materials can be poured, but they require professional installation). Other types require professional installation.
When hiring a professional certified installer:
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.
If you choose to install the insulation yourself, follow the manufacturer’s instructions and safety precautions carefully and check local building and fire codes. Do-it-yourself instructions are available from the fiberglass and mineral wool trade group. The cellulose trade group recommends hiring a professional, but if there isn’t a qualified installer in your area or you feel comfortable taking on the job, you may be able to find guidance from manufacturers.
The table below provides an overview of most available insulation materials, how they are installed, where they're typically installed, and their advantages.
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: 2 inch x 4 inch walls can hold R-13 or R-15 batts; 2 inch x 6 inch walls can use R-19 or R-21 products. 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 handling and fastening during installation.
Work with your manufacturer and/or local building supplier to determine actual thickness, R-value, and cost of fiberglass blankets and batts.
Concrete blocks are used to build home foundations and walls, and there are several ways to insulate them. If the cores aren’t filled with steel and concrete for structural reasons, they can be filled with insulation, which raises the average wall R-value. Field studies and computer simulations have shown, however, that core filling of any type offers little fuel savings, because heat is readily conducted through the solid parts of the walls.
It is more effective to install insulation over the surface of the blocks either on the exterior or interior of the foundation walls. Placing insulation on the exterior has the added advantage of containing the thermal mass of the blocks within the conditioned space, which can moderate indoor temperatures.
Some manufacturers incorporate polystyrene beads into concrete blocks, while others make concrete blocks that accommodate rigid foam inserts.
In the United States, two varieties of solid, precast autoclaved concrete masonry units are now available: autoclaved aerated concrete (AAC) and autoclaved cellular concrete (ACC). This material contains about 80% air by volume and has been commonly used in Europe since the late s. Autoclaved concrete can have up to ten times the insulating value of conventional concrete. The blocks are large, light, and easily sawed, nailed, and shaped with ordinary tools. The material absorbs water readily, so it requires protection from moisture. Precast ACC uses fly ash instead of high-silica sand, which distinguishes it from AAC. Fly ash is a waste ash produced from burning coal in electric power plants.
Hollow-core units made with a mix of concrete and wood chips are also available. They are installed by stacking the units without using mortar (dry-stacking) and filling the cores with concrete and structural steel. One potential problem with this type of unit is that the wood is subject to the effects of moisture and insects.
Concrete block walls are typically insulated or built with insulating concrete blocks during new home construction or major renovations. Block walls in existing homes can be insulated from the inside. Go to insulation materials for more information about the products commonly used to insulate concrete block.
Insulating concrete forms (ICFs) are basically forms for poured concrete walls, which remain as part of the wall assembly. This system creates walls with a high thermal resistance, typically about R-20. Even though ICF homes are constructed using concrete, they look like traditional stick-built homes.
ICF systems consist of interconnected foam boards or interlocking, hollow-core foam insulation blocks. Foam boards are fastened together using plastic ties. Along with the foam boards, steel rods (rebar) can be added for reinforcement before the concrete is poured. When using foam blocks, steel rods are often used inside the hollow cores to strengthen the walls.
The foam webbing around the concrete-filled cores of blocks can provide easy access for insects and groundwater. To help prevent these problems, some manufacturers make insecticide-treated foam blocks and promote methods for waterproofing them. Installing an ICF system requires an experienced contractor.
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 products contain 40% to 60% recycled glass. Mineral wool is usually produced from 75% post-industrial recycled content.
Some less common loose-fill insulation materials include polystyrene beads and perlite. Loose-fill insulation can be installed in either enclosed cavities such as walls, or unenclosed spaces such as attics. Cellulose, fiberglass, and rock wool are typically blown in by experienced installers skilled at achieving the correct density and R-values. Polystyrene beads, vermiculite, and perlite are typically poured.
The Federal Trade Commission has issued the “Trade Regulation Rule Concerning the Labeling and Advertising of Home Insulation” (16 CFR Part 460). The Commission issued the R-value Rule to prohibit, on an industry-wide basis, specific unfair or deceptive acts or practices. The Rule requires that manufacturers and others who sell home insulation determine and disclose each products’ R-value and related information (e.g., thickness, coverage area per package) on package labels and manufacturers’ fact sheets. R-value ratings vary among different types and forms of home insulations and among products of the same type and form.
For loose-fill insulation, each manufacturer must determine the R-value of its product at settled density and create coverage charts showing the minimum settled thickness, minimum weight per square foot, and coverage area per bag for various total R-values.
This is because as the installed thickness of loose-fill insulation increases, its settled density also increases due to compression of the insulation under its own weight. Thus, the R-value of loose-fill insulation does not change proportionately with thickness. The manufacturers’ coverage charts specify the bags of insulation needed per square foot of coverage area; the maximum coverage area for one bag of insulation; the minimum weight per square foot of the installed insulation; and the initial and settled thickness of the installed insulation needed to achieve a particular R-value.
Unlike most common insulation systems, which resist conductive and convective heat flow, radiant barriers and reflective insulation work by reflecting radiant heat. Radiant barriers are installed in homes -- usually in attics -- primarily to reduce summer heat gain, which helps lower cooling costs. Reflective insulation incorporates reflective surfaces -- typically 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 a large 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.
Rigid fiber or fibrous board insulation consists of either fiberglass or mineral wool material and is primarily used for insulating air ducts in homes. It is also used when there's a need for insulation that can withstand high temperatures. These products come in a range of thicknesses from 1 inch to 2.5 inches.
Installation in air ducts is usually done by HVAC contractors, who fabricate the insulation at their shops or at job sites. On exterior duct surfaces, they can install the insulation by impaling it on weld pins and securing with speed clips or washers. They can also use special weld pins with integral-cupped head washers. Unfaced boards can then be finished with reinforced insulating cement, canvas, or weatherproof mastic. Faced boards can be installed in the same way, and the joints between boards sealed with pressure-sensitive tape or glass fabric and mastic.
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.
There are two types of foam-in-place insulation: closed-cell and open-cell. Both are typically made with polyurethane. With closed-cell foam, the high-density cells are closed and filled with a gas that helps the foam expand to fill the spaces around it. Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture.
The type of insulation you should choose depends on how you will use it and on your budget. While closed-cell foam has a greater R-value and provides stronger resistance against moisture and air leakage, the material is also much denser and is more expensive. Open-cell foam is lighter and less expensive but should not be used below ground level where it could absorb water. Consult a professional insulation installer to decide what type of insulation is best for you.
Other available foam insulation materials include:
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 only 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.
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SIPs are made in a factory and shipped to job sites. Builders then connect them together to construct a house. For an experienced builder, a SIPs home goes up much more quickly than other homes, which saves time and money without compromising quality. These savings can help offset the usually higher cost of SIPs.
Many SIP manufacturers also offer "panelized housing kits." The builder need only assemble the pre-cut pieces, and additional openings for doors and windows can be cut with standard tools at the construction site.
When installed according to manufacturers' recommendations, SIPs meet all building codes and pass the American Society for Testing and Materials (ASTM) standards of safety.
Fire safety is a concern, but when the interior of the SIP is covered with a fire-rated material, such as gypsum board, it protects the facing and foam long enough to give building occupants a chance to escape.
As in any house, insects and rodents can be a problem. In a few cases, insects and rodents have tunneled throughout the SIPs, and some manufacturers have issued guidelines for preventing these problems, including:
Boric acid-treated insulation panels are also available. These panels deter insects, but are relatively harmless to humans and pets.
Because it can be very airtight, a well-built SIP structure may require controlled fresh-air ventilation for safety, health, and performance, and to meet many building codes. A well-designed, installed, and properly operated mechanical ventilation system can also help prevent indoor moisture problems, which is important for achieving the energy-saving benefits of a SIP structure.
Fiberglass consists of extremely fine glass fibers and is one of the most ubiquitous insulation materials. It's commonly used in many different forms of insulation: blanket (batts and rolls), loose-fill, and is also available as rigid boards and duct insulation.
Manufacturers now produce medium- and high-density fiberglass batt insulation products that have slightly higher R-values than the standard batts. The denser products are intended for insulating areas with limited cavity space, such as cathedral ceilings.
High-density fiberglass batts for a 2 by 4-inch (51 by 102 millimeter [mm]) stud-framed wall has an R-15 value, compared to R-11 for "low density" types. A medium-density batt offers R-13 for the same thickness. High-density batts for a 2 by 6-inch (51 by 152 mm) frame wall offer R-21, and high-density batts for an 8.5-inch (216-mm) spaces yield about an R-30 value. R-38 batts for 12-inch (304-mm) spaces are also available.
Fiberglass insulation is made from molten glass that is spun or blown into fibers. Most manufacturers use up tp 40% to 60% recycled glass content. Loose-fill insulation must be applied using an insulation-blowing machine in either open-blow applications (such as attic spaces) or closed-cavity applications (such as those found inside existing walls or covered attic floors). Learn more about where to insulate.
One variation of fiberglass loose-fill insulation is the Blow-In-Blanket System® (BIBS). BIBS is blown in dry, and tests have shown that walls insulated with a BIBS system are significantly better filled than those insulated using other forms of fiberglass insulation such as batts because of the effective coverage obtained by this method of application.
The newer BIBS HP is an economical hybrid system that combines BIBS with spray polyurethane foam.
Cellulose insulation is made from recycled paper products, primarily newsprint, and has a very high recycled material content, generally 82% to 85%. The paper is first reduced to small pieces and then fiberized, creating a product that packs tightly into building cavities.
Manufacturers add the mineral borate, sometimes blended with the less costly ammonium sulfate, to ensure fire and insect resistance. Cellulose insulation, when installed at proper densities, cannot settle in a building cavity.
Cellulose insulation is used in both new and existing homes, as loose-fill in open attic installations and dense packed in building cavities such as walls and cathedral ceilings. In existing structures, installers remove a strip of exterior siding, usually about waist high; drill a row of three-inch holes, one into each stud bay, through the wall sheathing; insert a special filler tube to the top of the wall cavity; and blow the insulation into the building cavity, typically to a density of 1.5 to 3.5 lb. per cubic foot. When installation is complete, the holes are sealed with a plug and the siding is replaced and touched up if necessary to match the wall.
In new construction, cellulose can be either damp-sprayed or installed dry behind netting. When damp sprayed, a small amount of moisture is added at the spray nozzle tip, activating natural starches in the product, and causing it to adhere inside the cavity. Damp-sprayed cellulose is typically ready for wall covering within 24 hours of installation. Cellulose can also be blown dry into netting stapled over building cavities.
Polystyrene--a colorless, transparent thermoplastic--is commonly used to make foam board or beadboard insulation, concrete block insulation, and a type of loose-fill insulation consisting of small beads of polystyrene.
Molded expanded polystyrene (MEPS), commonly used for foam board insulation, is also available as small foam beads. These beads can be used as a pouring insulation for concrete blocks or other hollow wall cavities, but they are extremely lightweight, take a static electric charge very easily, and are notoriously difficult to control.
Other polystyrene insulation materials similar to MEPS are expanded polystyrene (EPS) and extruded polystyrene (XPS). EPS and XPS are both made from polystyrene, but EPS is composed of small plastic beads that are fused together and XPS begins as a molten material that is pressed out of a form into sheets. XPS is most commonly used as foam board insulation. EPS is commonly produced in blocks, which can easily be cut to form board insulation. Both EPS and XPS are often used as the insulation for structural insulating panels (SIPs) and insulating concrete forms (ICFs). Over time, the R-value of XPS insulation can drop as some of the low-conductivity gas escapes and air replaces it--a phenomenon is known as thermal drift or aging.
The thermal resistance or R-value of polystyrene foam board depends on its density. Polystyrene loose-fill or bead insulation typically has a lower R-value compared to the foam board.
Polyisocyanurate or polyiso is a thermosetting type of plastic, closed-cell foam that contains a low-conductivity, hydrochlorofluorocarbon-free gas in its cells.
Polyisocyanurate insulation is available as a liquid, sprayed foam, and rigid foam board. It can also be made into laminated insulation panels with a variety of facings. Foamed-in-place applications of polyisocyanurate insulation are usually cheaper than installing foam boards, and can perform better because the liquid foam molds itself to all of the surfaces.
Over time, the R-value of polyisocyanurate insulation can drop as some of the low-conductivity gas escapes and air replaces it -- a phenomenon is known as thermal drift or ageing. Experimental data indicates that most thermal drift occurs within the first two years after the insulation material is manufactured.
Foil and plastic facings on rigid polyisocyanurate foam panels can help slow down the aging process. Reflective foil, if installed correctly and facing an open air space, can also act as a radiant barrier. Depending upon the size and orientation of the air space, this can add another R-2 to the overall thermal resistance.
Some manufacturers use polyisocyanurate as the insulating material in structural insulated panels (SIPs). Foam board or liquid foam can be used to manufacture a SIP. Liquid foam can be injected between two wood skins under considerable pressure, and, when hardened, the foam produces a strong bond between the foam and the skins. Wall panels made of polyisocyanurate are typically 3.5 inches (89 mm) thick. Ceiling panels are up to 7.5 inches (190 mm) thick. These panels, although more expensive, are more fire and water vapor-diffusion resistant than EPS. They also insulate 30% to 40% better for given thickness.
Polyurethane is a thermoset foam insulation material that contains a low-conductivity gas in its cells. Polyurethane foam insulation is available in closed-cell and open-cell formulas. With closed-cell foam, the high-density cells are closed and filled with a gas that helps the foam expand to fill the spaces around it. Open-cell foam cells are not as dense and are filled with air, which gives the insulation a spongy texture and a lower R-value.
Like polyiso foam, the R-value of closed-cell polyurethane insulation can drop over time as some of the low-conductivity gas escapes and air replaces it in a phenomenon known as thermal drift or ageing. Most thermal drift occurs within the first two years after the insulation material is manufactured, after which the R-value remains unchanged unless the foam is damaged.
Foil and plastic facings on rigid polyurethane foam panels can help slow down thermal drift. Reflective foil, if installed correctly and facing an open air space, can also act as a radiant barrier. Depending upon the size and orientation of the air space, this can add another R-2 to the overall thermal resistance.
Polyurethane insulation is available as a liquid sprayed foam and rigid foam board. It can also be made into laminated insulation panels with a variety of facings.
Sprayed or foamed-in-place applications of polyurethane insulation are usually cheaper than installing foam boards, and these applications usually perform better because the liquid foam molds itself to all of the surfaces. All closed-cell polyurethane foam insulation made today is produced with a non-HCFC (hydrochlorofluorocarbon) gas as the foaming agent.
Low-density, open-cell polyurethane foams use air as the blowing agent and have an R-value that doesn't change over time. These foams are similar to conventional polyurethane foams but are more flexible. Some low-density varieties use carbon dioxide (CO2) as the foaming agent.
Low-density foams are sprayed into open wall cavities and rapidly expand to seal and fill the cavity. Slow expanding foam is also available, which is intended for cavities in existing homes. The liquid foam expands very slowly, reducing the chance of damaging the wall from overexpansion. The foam is water vapor permeable, remains flexible, and is resistant to wicking of moisture. It can provide good air sealing, is fire resistant, and won't sustain a flame.
Soy-based, polyurethane liquid spray-foam products are also available. These products can be applied with the same equipment used for petroleum-based polyurethane foam products.
Some manufacturers use polyurethane as the insulating material in structural insulated panels (SIPs). Foam board or liquid foam can be used to manufacture a SIP. Liquid foam can be injected between two wood skins under considerable pressure, and, when hardened, the foam produces a strong bond between the foam and the skins. Wall panels made of polyurethane are typically 3.5 inches (89 mm) thick. Ceiling panels are up to 7.5 inches (190 mm) thick. These panels, although more expensive, are more fire and water vapor-diffusion resistant than EPS. They also insulate 30% to 40% better for given thickness.
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