Insulation - New And Alternative Insulation Materials And Products - 5/1/2004 - House Energy Efficiency Insulation

Insulation - New And Alternative Insulation Materials And Products

Many of the thermal insulation materials and products discussed below are intended as alternatives to more commonly used types. Manufacturer and product names have been intentionally omitted unless necessary to convey an adequate description of the material.

Fiberglass: Some manufacturers now produce medium and high-density fiberglass batt insulation products that have slightly higher R-values (ft2h° F/Btu) than previous varieties. The denser products are intended for insulating areas with limited cavity space, such as cathedral ceilings.

High-density fiberglass batts for a 2 x 4 inch (51 x 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 space. High-density batts for a 2 x 6 inch (51 x 152 mm) frame wall offer R-21. High-density batts for an 8.5 inch (216 mm) spaces offer about R-30. R-38 for 12 inch (304 mm) spaces are available too.

One manufacturer markets an unconventional fibrous insulation product. It is a combination of two types of glass that are fused together. As the two materials cool during manufacturing they form random curls of the material. This makes the material less irritating and possibly safer to work with and it requires no chemical binder to hold the batts together. It also comes in a perforated plastic sleeve to assist in handling.

There are also several variations of loose fiberglass intended for use with insulation blowing machines. Some products claim higher recycled material content, or some other marketing theme, that can make them stand out from the competition. However, they all provide similar thermal performance.

One significant variation is the Blown-In-Blanket (BIB.) This is similar to the more common "wet-spray" cellulose in that the material is mixed with a latex adhesive, misted with water to activate the glue, and blown into wall stud cavities. Tests have shown that walls insulated with a BIB system are significantly better filled than with other forms of fiberglass insulation, such as batts.

Mineral Wool: The term "mineral wool" refers to three types of insulation that are basically the same:
* "glass wool," or "fiberglass," made from recycled glass;
* "rockwool," made from basalt, an igneous rock; and
* "slag wool," made from steel-mill slag.

Most mineral wool made in the United States is actually slag wool. Most mineral wool is a brittle/ loose material. Mineral wool does not use additional chemicals to make it fire resistant.

Recently, a Canadian company began producing a softer, batt type mineral product. This batting is denser, fits standard wall cavities tighter, and is somewhat less prone to air convection thermal losses. Than standard fiberglass batt products. Its thermal resistance is approximately R-3.7 per inch, which is comparable with sprayed cellulose insulation or high-density fiberglass batts.

Plastic Fiber: Plastic fiber insulation is not readily available in most areas of the U.S. This material is made of mainly recycled plastic milk bottles (polyethylene terephthalate or PET.) The fibers are then formed into batt insulation similar to high-density fiberglass, and then treated with a fire retardant. R-values vary with batt density: R-3.8 per inch at 1.0 lb./ft3 density to R-4.3 per inch at 3.0 lb/ft3 density. Plastic fiber insulation is relatively non-irritating to work with and doesn't readily burn. It does, however, melt when exposed to flame. The batts are also reportedly difficult to handle and cut with standard job-site tools. 

Polyurethane Foams: All closed-cell polyurethane foam insulation made today is produced with a non-CFC (chlorofluorocarbon) gas as the blowing agent. This gas doesn't insulate as well as insulation made with a CFC gas, however it is less destructive to our planet's ozone layer. Foams made in this way have an aged R-value of R-6.5 per inch thickness. Their density is generally 2.0 lb/ft3 (32.0 kilograms per cubic meter [kg/m3]). There are also low-density open-cell polyurethane foams (0.5 lb/ft3 [8 kg/m3]). These are similar to conventional polyurethane foams, but are more flexible. Some low-density varieties use carbon dioxide (CO2) as the blowing agent.

Low-density foams are sprayed into open wall cavities and rapidly expand to seal and fill the cavity. There is at least one manufacturer who offers a slow expanding foam. This type is intended for cavities in existing construction where there is no insulation. The liquid foam expands very slowly and thus reduces the chance of damaging the wall from over-expanding. The foam is water vapor permeable, remains flexible, and is resistant to wicking of moisture. It provides good air sealing and yields about R-3.6 per inch of thickness. It is also fire resistant and will not sustain a flame upon removal of the flame source.

Soy-based polyurethane foam products are also available. These products use a spray-in-place foam derived from soy beans. The cured R-value ranges from 3.8 per inch to 7. It can be applied with the same equipment as is used for petroleum-based polyurethane foam products.

Nitrogen-based Urea-Formaldehyde (UF) Foam: Urea-Formaldehyde (UF) foam was used in residential housing during the 1970's. However, after many health related court cases due to improper installation practices, it was removed from the residential market and is now used primarily for masonry walls in commercial/industrial buildings. This type of foam insulation uses compressed air as the expanding agent. Nitrogen-based, UF foam may take several weeks to cure completely. Unlike polyurethane insulation, this product does not expand as it cures and also allows water vapor to easily pass through it. UF foam also breaks down at prolonged temperatures above 190° F (88° C) and contains no fire retardant chemicals. This insulation has an R-value of about 4.6 per inch and costs are competitive with loose-fill or poured-in insulation.

Phenolic Foam: This type of foam was somewhat popular years ago as a rigid foam board insulation. It is currently available only as a foamed-in-place insulation. It has a R-4.8 value per inch of thickness and uses air as the blowing agent. One major disadvantage of phenolic foam that it can shrink up to 2% after curing. This makes it less popular today, since there are alternatives that do not have this disadvantage. 

Cementitious Foam: Air-Krete(tm) is a magnesium silicate, cementitious (cement-based) insulation that is foamed and pumped into closed cavities. The initial consistency of the foam is similar to shaving cream and after curing is similar to a thick pudding. It is easily damaged by water since it is made from minerals extracted from seawater. It is non-toxic and doesn't burn. It has an R-value of about 3.9 per inch and costs about as much as polyurethane foam. 

Foaming Insulation Vehicles: These are latex-based foamed adhesives that transport an insulating material (such as fiberglass) into a cavity. After the bubbles in the foam dissipates, it leaves the encapsulated insulation uniformly distributed in the cavity and it's R-value unchanged. It is intended for enclosed building cavities. It is not widely available in the U.S. Here are typical R-values attained for three types of insulation applied in this manner:
Fiberglass: R-4.0 per inch 
Mineral Wool: R-3.8 per inch
Cellulose: R-3.7 per inch 

Structural Insulating Panels (SIP): Structural insulating panels (SIP) often consists of a foam board core sheathed on one or both sides with plywood, oriented strand board (OSB), or gypsum board (drywall.) The insulation is usually polystyrene or isocyanurate, but foam-straw composites are sometimes used too. Panels range in size, but are most common in 4 x 8 foot to 4 x 10 foot (1.2 x 2.4 meter to 1.2 x 3.04 meter).

Because of their structural strength, SIPs reduce the need for structural lumber, opportunities for air leaks, and installation errors common with stud frame (stick-built) construction. It is also faster to build SIP wall assembles than many other construction methods. Most comparison studies between stick-built and SIP house show significant energy saving with the SIPs. Because these panels also reduce sound transmission, some designers use them for interior partitions too.

SIP roof panels sometimes have a nailable layer only on one side. It's purpose is as a retrofit over an existing roof where additional insulation is desired but no attic exists under the roof deck. The insulated roof panels are also available with air channels just under the exterior sheathing for ventilated roof designs.

Insulating Concrete Forms (ICF): An ICF system consists of interlocking foam board and occasionally hollow-core foam blocks. The foam board forms are held vertical and parallel to each other by plastic or steel rods and ties. After adding the appropriate reinforcing steel rods (rebar) and poured concrete, the result is a very strong and insulated concrete wall. Such a building can be made from foundation to roofline. Some innovative builders make the roof of ICF as well.

Because of its flammability, any ICF exposed to the occupied space must be covered with an appropriate fire-resistant material. Most codes find half-inch (12.7mm) drywall acceptable. The exterior of the building can be finished with anything the designer finds desirable.

Other systems use the rigid insulation board in the center of the concrete wall. These are often referred to as "tilt-wall" construction. The walls are poured in a form on a flat deck and after curing are "tilted" upright into position by a crane. Because the insulation board is inside the wall it reduces problems relating to fire and insect infestation.

Insulation block systems are typically hollow core polystyrene blocks that interlock to create the ICF wall system. Steel reinforcing rods are often used inside the block cavities to strengthen the wall. One draw-back of stacked block ICFs is that the foam webbing around the concrete filled cores provides easy access for insects and ground water to enter the building. To minimize these problems, some manufacturers make insecticide treated forms and often promote a water proofing method for the foam blocks.

Concrete Block Insulation: Insulated concrete blocks take on many different shapes and compositions. The better concrete masonry units reduce the area of connecting webs as much as possible. The cores are filled with insulation-poured-in, blown-in, or foamed-in-except for those cells requiring structural steel reinforcing and concrete infill. This raises the average wall R-value. 

Some block makers coat polystyrene beads with a thin film of concrete. The concrete serves to bond the polystyrene while providing limited structural integrity. Expanded polystyrene mixed with Portland cement, sand, and chemical additives are the most common group of ingredients. These make surface bonded wall assemblies with a wall R-value of R-1 per inch thickness. Polystyrene inserts placed in the block cores increase the unit thermal resistance to about R-2 per inch.

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). Structural stability comes from the concrete fill and appropriate rebar throughout for structural walls. One detracting point of this type is that the wood component is subject to the effects of moisture and insects.

Two varieties of solid, precast autoclaved concrete masonry units are now available in the U.S.: autoclaved aerated concrete (AAC), and autoclaved cellular concrete (ACC). This class of material has been commonly used in European construction since the late 1940s. Air makes up 80% (by volume) of the material. It has ten times the insulating value of conventional concrete. The R-1.1 per inch blocks are large, light, and have a flat surface that looks like a hard, fine sponge. Mastic or a thin mortar is used to construct a wall. The wall then often gets a layer of stucco as the finish. Autoclaved concrete is easily sawn, nailed, and shaped with ordinary tools. Since the material absorbs water readily, it requires protection from moisture. 

Precast autoclaved cellular concrete uses fly ash instead of high-silica sand as its distinguishing component. Fly ash is a waste ash produced from burning coal in electric power plants. The fly ash is the material that differentiates ACC from AAC.

Specialized Devices: A wide variety of rigid insulation inserts are available to fill many critical locations in the insulated envelope of houses. Some examples are to use inserts as air chutes, insulation dams, concrete block fillers, and ice dam retarders. Expanding foams efficiently seal and weatherize homes. Devices as simple as cardboard can be used to provide an insulation dam to help keep loose-fill insulating material around attic ductwork. 

Natural Fibers: Several natural fibers are being analyzed for their potential insulating properties. The most notable of these include cotton, wool, hemp, and straw.

Cotton thermal insulation is no longer produced in the United States, however you may still be able to find small quantities in some areas. Cotton based insulation consists of recycled cotton and plastic fibers that have been treated with the same flame retardant and insect/rodent repellent as cellulose insulation. It meets the same Class I standards for fire resistance as fiberglass insulation. Cotton insulation has similar thermal properties as fiberglass and cellulose insulation (R-3 or so per inch of thickness.) Some chemically sensitive consumers feel that this type of insulation is "healthier" to use than other types. However, field studies have proven that this is generally not the case, and other sources of indoor air pollution are of more concern than the type of insulation.

Wool and hemp insulation are relatively unknown in the U.S., but have been in use in other, less industrialized countries. Both products offer similar R-values to other fibrous insulation types (about R-3.5 per inch of thickness.)

Straw bale construction, popular 150 years ago on the Great Plains of the United States, is receiving renewed interest. Straw bales tested by the Oak Ridge National Laboratory yielded R-values of R-2.4 to R-3.0 per inch. But at least one straw bale expert claims R-2.4 per inch is more representative of typical straw bale construction due to the many gaps between the stacked bales. 

Straw Panels: The process of fusing straw into boards without adhesives was developed in the 1930s. Panels are usually 2 to 4 inches (51-102 mm) thick and faced with heavyweight Kraft paper on each side. Although manufacturer's claims vary, R-values realistically range from about R-1.4 to R-2 per inch. They also make effective sound-absorbing panels for interior partitions. Some manufacturers have developed SIPs from multiple-layered, compressed-straw panels.

Many types of insulation products are rapidly becoming incorporated into conventional construction. They may provide a convenient or sometimes a healthier approach to increasing the energy efficiency of a building. However, it is important to note that because some materials have been on the market for only a short time they may not be widely available and performance and durability of some materials may not be well documented. Always carefully research material characteristics for suitability for your purposes.

Note: The standard unit of measurement in the United States has been the Imperial unit. To differentiate it from the metric system the term 'SI' is used. For example, RSI refers to the R-value in International System (SI) or metric units. 

Reflective Insulation

Reflective insulation systems are fabricated from aluminum foils with a variety of backings such as kraft paper, plastic film, polyethylene bubbles, or cardboard. The resistance to heat flow depends on the heat flow direction, and this type of insulation is most effective in reducing downward heat flow. Reflective systems are typically located between roof rafters, floor joists, or wall studs. If a single reflective surface is used alone and faces an open space, such as an attic, it is called a radiant barrier. Radiant barriers are sometimes used in buildings to reduce summer heat gain and winter heat loss. They are more effective in hot climates than in cool climates. All radiant barriers must have a low emittance (0.1 or less) and high reflectance (0.9 or more). See Radiant Barriers section.

Rolls And Batts

Rolls and batts-or blankets-are flexible products made from mineral fibers, such as fiberglass and rockwool. They are available in widths suited to standard spacings of wall studs and attic or floor joists. Continuous rolls can be hand-cut and trimmed to fit. They are available with or without vapor retarder facings. Batts with a special flame-resistant facing are available in various widths for basement walls where the insulation will be left exposed.

Foam And Foam Board Insulation

Even though many foam insulation products are more expensive than other types of insulating materials, such as fiberglass, cellulose, etc., they are commonly used in buildings where there are space limitations or where very high R-values are desirable. Foam insulation R-values range from R-4 to R-8 per inch of thickness (2.54 cm), which is 2 to 3 times greater than most other insulating materials of the same thickness. Also, if all the materials are carefully installed, foam insulation may control air infiltration more effectively than other types of insulation.

Several variables affect the installed R-value of foam insulation, including: the initial density of the foam; the blowing gas used (CFC, HCFC, CO2, air, or a number of other gases); how the foam insulation is handled (dents and chips adversely effect the R-value); the type of facing (if any) used; and the conditions in which the foam is installed.

Foam insulation is often made with one of three materials: molded expanded polystyrene (MEPS), extruded expanded polystyrene (XEPS) or polyurethane, polyisocyanurate, or a related chemical mixture. Some are installed as a liquid while other types come as factory-made panels called rigid foam boards. Some are installed as a liquid while other types come as factory made panels or "foam board." 

Although batts are typically used between studs or floor joists, rigid foam boards should be considered as an alternate approach. These boards are lightweight, and provide structural support and acoustical insulation. Rigid boards can be added to attic access, basement walls, exposed foundations, cathedral ceilings, and exterior walls. Such boards may be faced with a reflective foil that reduces heat flow when next to an air space. Check your local fire codes, because often these boards must be covered with a fire barrier, such as gypsum wallboard. 

Liquid foam insulation can be sprayed into building cavities as a liquid or in larger quantities as a pressure-sprayed product (foamed-in-place). Both types expand and harden as the chemical mixture cures. It also conforms to the shape of the cavity to fill and seal it thoroughly. This type is often used in new construction. It can completely conform to a building cavity, sealing it thoroughly. Therefore, it's good to use in areas where it would be difficult to fit rigid boards. If you spray this insulation into an enclosed space, be careful that you don't use too much, because that could cause other parts of the structure to bend or break. 

There are also slow curing liquid foams that are designed to flow over obstructions before it expands and cures. This type is often used for empty wall cavities in existing buildings. There are also liquid foam materials that are poured from a container.

Both are generally urethane foams. Latex , phenolic, and organic based foams are available too, but they do not have as high an R-value as urethane-based products. Be aware that these alternatives do not have as high an R-value as a urethane-based products.

Molded Expanded Polystyrene (MEPS) Foam Board: MEPS is a closed-cell material that can be molded into many everyday items, such as coffee cups and shipping materials, or into large sheets as construction insulation. This material is commonly known as "beadboard," and it has an R-value of about 4 per inch of thickness [2.54 cm].

To make beadboard, loose, unexpanded polystyrene beads containing liquid pentane are mixed with a blowing agent and poured into an enclosed container. The mixture is then heated to expand the beads many times their original size. The beads are then injected into a mold and under more heat and pressure expand to become foam blocks that are then shaped as required. 

The physical properties of Molded Expanded Polystyrene varies with the type of bead used, but the density of the board is usually one pound per cubic foot (16.3 kilograms per cubic meter.) Beadboard is manufactured at various densities, depending on the application. Beadboard for roofing materials has to be dense enough to walk on without damage. Wall insulation boards are several times less dense than roof boards. R-values range from 3.8 to 4.4 per inch (2.54 cm) of thickness. Since spaces between the foam beads can absorb water, a vapor diffusion retarder is necessary if water transmission through the insulation might present a problem for the user. 

Molded Expanded Polystyrene foams are also available as small beads of foam too. This type is often used as a pouring insulation for concrete blocks or other hollow wall cavities. However, be aware that poured beads are extremely light-weight and take a static electric charge very easily. They are notoriously difficult to control and any wind at all often results in the beads flying all over the place. Also, if there is ever a hole in the wall the foam beads will continue to fall out of the hole until the wall is almost empty of beads.

Extruded Expanded Polystyrene (XEPS) Foam Board: Extruded expanded polystyrene (XEPS) is a closed-cell foam insulation similar to MEPS. To make it, the polystyrene pellets are mixed with various chemicals to liquefy them. A blowing agent is then injected into the mixture, forming gas bubbles. The foaming, thick liquid is then forced through a shaping die. When cooled, the panel is cut as required. Foam densities are typically 1.5 pounds per cubic foot (0.21 kilograms per cubic meter).

Extruded Expanded Polystyrene is more expensive than Molded Expanded Polystyrene, and like MEPS the R-value depends upon the density of the material. Generally, it's about R-5 per inch. It is also much more consistent in density and has a higher compressive strength than MEPS, making it better suited for use on roofs or for wall panels. Extruded polystyrene also has excellent resistance to moisture absorption.

Both Molded Expanded Polystyrene and Extruded Expanded Polystyrene are often used as the insulation for Structural Insulating Panels (SIPs) and as Insulating Concrete Forms (ICFs.)

Polyurethane and Polyisocyanurate: Polyurethane and polyisocyanurate are both closed-cell foams that contain a low-conductivity gas in the cells (usually one of the HCFC or CFC gases.) The high thermal resistance of the gas gives these foams an R-value of between R-7 and R-8 per inch.

Both types are available as a liquid spray, poured foam and also as rigid boards. They can also be made into laminated panels with a variety of facings. Foamed-in-place applications are usually cheaper than installing foam boards and perform better since it molds itself to all of the surfaces perfectly. However, be sure you use a contractor with plenty of experience with spray foam installations.

Over time, the R-value of the foam drops as some of the gas escapes and air replaces it. This phenomenon is known as thermal drift. When manufactured, the initial R-value is roughly R-9 per inch. Experimental data on this type of foam indicates that most thermal drift occurs within the first two years after manufacture and slowly decreases until it stabilizes at about R-7 per inch. It then remains unchanged unless the foam is damaged.

Foil and plastic facings on these foam panels help to slow the escape of gas from the cell structure. Testing suggests that the stabilized R-value of rigid foam with metal foil facings remains unchanged after 10 years. The reflective foil, if installed correctly, can also act as a radiant barrier (another type of insulation) that adds about R-2 to the insulating assembly. Panels with foil facings have stabilized R-values of 7.1 to 8.7 per inch. 

Common Applications of Foam Insulation: Spray foam and foam boards can be used to insulate almost anything, including: roofs, walls, foundations, entry and overhead garage doors, pipes and tanks, under basement slabs, or over a slab-on-grade floor. Foam insulation sprayed or placed in wall and floor cavities both insulates and offers some degree of soundproofing.

Protect all types of foam insulation from direct sunlight. Over time, the sun's ultraviolet rays can damage them. For roofs this is generally done by applying a coating such as tar, acrylic, silicone or rubberized paint. You can also cover the foam with a rubber or plastic membrane or a layer of asphalt and roofing felt. Make certain you are using compatible products. The solvents in some coatings dissolve certain plastics.

There are several ways to incorporate foam insulation in concrete or masonry walls: pouring loose foam beads into masonry blocks; injecting/ pouring liquid foam into the hollow block cores; manufacturing concrete blocks to accommodate rigid foam inserts; as lightweight concrete blocks that have polystyrene beads in the concrete mixture; and as rigid foam insulation inside a cast-in-place wall. There are also interlocking rigid foam panels and blocks that serve as permanent forms for concrete walls and foundations. These are commonly known as Insulating Concrete Forms (ICF's.) 

Potential Moisture Problems: In cold weather, warm inside air containing water vapor can get past the wall finish and insulation and condense inside the colder wall cavity. In hot-humid climates the same thing can happen, just in the reverse direction, humid outdoor air in the summer can condense inside cool/air-conditioned wall cavities. If enough of this happens, and the water cannot escape, wood rot, mold, and other moisture-related problems are likely to occur. For this reason, building codes often require installing a vapor diffusion retarder on the warmest side of the wall cavity.

Foam board insulation is commonly placed between the exterior finish (i.e., siding, brick) and the studs of exterior walls. To prevent air infiltration, you should place rigid insulation boards tightly together and seal the seams with tape or caulk. However, this practice may worry some builders in cold climates since the foam board may act as a second vapor diffusion retarder. Studies have shown, however, that condensation rarely occurs in these areas unless something else is seriously wrong with the wall assembly (i.e., massive uncontrolled air leakage into the walls from the house.) If the assembly is constructed correctly, the inside surface of the foam board stays warm enough to keep water vapor in its gaseous state long enough for it to escape.

Insect Problems: When insulating a foundation, and although foam insulation offers no food value to insects, foam board provides the potential for easy insect tunneling. Insect burrows reduce the R-value and structural integrity of the insulation. For these reasons, some manufacturers treat their foam products with an insecticide, usually a borate compound. Many building jurisdictions also mandate treating the earth around the building with insecticides and keeping an area bare of insulation board, several inches wide, and all the way around the foundation of a house as an inspection area. 

Another option for insulating below grade walls is to install the foam board on the interior of the basement walls. Interior applications prevent ground-dwelling insects from finding the foam board at all, and it eliminates the need for the bare inspection area. Insulating interior walls, however, requires careful attention to moisture control. Moisture intrusion through the wall from the soil, and moisture in humid air from the interior, can condense on the interior surface of the basement wall. This can lead to mold and mildew and rotting of the wall covering material. 

A better solution for below grade walls in need of insulation is to install the foam board over the interior of the basement walls rather than on the exterior as is more commonly done. Interior applications prevent ground-dwelling insects from finding the foam board at all, and it eliminates the need for the inspection area where no insulation is allowed. However, most jurisdictions require installing a fire-barrier over the foam board. While this adds extra cost, the thermal performance of this method is superior in most cases to the more common foam board application to the exterior of the foundation. This equates with a dollar savings in energy that can repay you many times over for the additional cost that an interior application requires. If you plan to convert a basement into a living space there is almost no additional cost.

Fire Protection: Foam insulation is relatively hard to ignite but when ignited, it burns readily and emits a dense smoke containing many toxic gases. The combustion characteristics of foam insulation varies with the combustion temperatures, chemical formulation, and available air. 

Because of the dangers described above, foams used for construction require a covering as a fire barrier. One half-inch thick (1.27 cm) gypsum wallboard is one of the most common fire barriers. Some building codes, however, do not require an additional fire barrier for certain metal-faced laminated foam products. Check with your local building code/fire officials, and insurers for specific information on what is permitted in your area. 

Loose-Fill Insulations

Summary: This section will introduce you to loose-fill insulation materials-what they are, how they are applied, how they compare with each other, and other considerations regarding their use-so that you can decide if they're right for your home. Whether you are increasing the insulation levels in your current home or selecting insulation for a new home, choosing the right insulation material can be challenging. Fibrous loose-fill insulations such as cellulose, fiberglass, and rockwool are options you may wish to consider. 

Loose-fill insulation-usually made of fiberglass, rockwool, or cellulose-comes in shreds, granules, or nodules. These small particles should be blown into spaces using special pneumatic equipment. The blown-in material conforms readily to building cavities and attics. Therefore, loose-fill insulation is well suited for places where it is difficult to install other types of insulation. Additional resistance to air infiltration can be provided if the insulation is sufficiently dense or thick. 

Manufacturers use recycled waste materials in the production of all three primary types of loose-fill insulation. Cellulose loose-fill insulation contains more than 75% recycled materials. Meanwhile, fiberglass insulation manufacturers use increasing amounts of recycled materials in their products, at least 20% to 30% recycled glass content. The production of rockwool uses byproducts that would otherwise be wasted. But loose-fill cellulose insulation require less energy to produce than other forms of insulation. 

The performance of loose-fill insulation is strongly affected by its installation. So be sure to read the labels on the bags, and to pay more attention to the installed R-value than to the installed thickness. The Insulation Contractor's Association of America gives other useful consumer tips about how to buy this type of insulation.

Character and Types of Loose-Fill Insulation: The most obvious difference between loose fills and other types of insulation is their form. They are either produced as-or broken down into-shreds, granules, or nodules. These small particles form fluffy materials that conform to the spaces in which they are installed. Loose fills are most commonly sold in bags and are blown into building cavities using special equipment. All three primary types of loose-fill insulation are considered "environmentally positive" because recycled waste materials are used in their production. 

Cellulose loose-fill insulation is made from wastepaper, such as used newsprint and boxes, that is shredded and pulverized into small, fibrous particles. Chemicals are added to provide resistance to fire and insects. Also, less energy is required to produce loose-fill cellulose than to produce other insulations. 

Fiberglass loose-fill insulation is spun from molten glass into fibers. The glass is typically melted in high-temperature gas furnaces. Most major manufacturers use 20% to 30% recycled glass content. 

Rockwool (or slag wool) loose-fill insulation is similar to fiberglass except that it is spun from blast furnace slag (the scum that forms on the surface of molten metal) and other rock-like materials instead of molten glass. The production of rockwool uses by-products that would otherwise be wasted. 

Primary Applications of Loose-Fill Insulations: Loose-fill insulations are well suited for places where it is difficult to install other types of insulation, such as irregularly shaped areas, around obstructions (such as plumbing stacks), and in hard-to-reach places. They can be installed in either enclosed cavities such as walls or unenclosed spaces such as attics. Blown-in loose fills are particularly useful for retrofit situations because, except for the holes that are sometimes drilled for installations, they are one of the few materials that can be installed without greatly disturbing existing finishes. Rockwool or slag wool loose-fill insulation is often used for insulating existing walls and ceilings in mobile homes. 

In most new construction, however, the more common choices in insulation are batts or rolls because they can be installed without the use of special equipment before walls are finished. Batts are available in standard widths designed to match the cavities created by wall studs. 

Loose fills are sometimes used in new construction, though. A mixture of loose-fill insulation and an adhesive can be sprayed into wall cavities before the walls are closed. Such methods may result in fewer gaps in the building's thermal envelope than can occur with batts. 

Comparative Performance of Loose-Fill Insulations: Insulation materials are compared on the basis of their R-values per unit of thickness, density per unit of volume, and weight per unit of area. 

There are several performance characteristics to consider when selecting an insulation material. Among the most important to compare are insulating capacity, weight, convective heat loss, settling and loss of insulating capacity, fire resistance, and moisture resistance. 

Insulating Capacity: A material's resistance to heat flow is expressed as its R-value. The higher the R-value, the better the material insulates, and the lesser the thickness you will need. (However, in an open, unrestricted attic application, the height limit of insulation thickness is of no great concern. But if you use your attic for storage, heavy objects will compress insulation and decrease its benefits.) Different insulations also have different densities, or weights. There are weight limits for certain ceiling types (see the chart and the section on Weight that follows). 

Weight limits and other factors at R-38 insulation levels are shown in the chart on this page for the three primary types of loose fills. (R-38 is a commonly recommended ceiling insulation level in many parts of the United States. 

Weight: Ceiling drywall can sag under heavy loads, such as those sometimes created by insulation. One drywall manufacturer recommends loads of no more than 1.3 pounds per square foot (6 kilograms per square meter) for 1/2-inch (1.3-centimeter) ceiling drywall with framing spaced 24 inches (61 centimeters) on center. The limit increases to 2.2 pounds per square foot (11 kilograms per square meter) for framing spaced 16 inches (41 centimeters) on center and for 5/8-inch (1.6-centimeter) drywall. 

Loose-fill cellulose and rockwool, being heavier materials, could cause the ceiling to sag if installed at R-38 on 1/2-inch (1.3-centimeter) ceiling drywall with framing spaced 24 inches (61 centimeters) on center (see chart). Therefore, when deciding whether to use these materials for new construction, consider switching to 5/8-inch ceiling drywall or, if possible, changing your ceiling framing widths to 16 inches on center. 

Some cellulose and rockwool insulation manufacturers include weight limit information on the bag. Because fiberglass is much less dense, its weight on ceiling dry-wall is not a concern. 

Convective Heat Loss: Convection is heat flow caused by air cur-rents. Convective heat loss in insulation is rare, but it can occur when large temperature differences above and below insulation create tiny air currents (called "convection loops") within the insulation. Studies have shown that convective heat loss can occur with lighter density loose-fill fiberglass at the very low attic temperatures possible in extremely cold climates. Depending on the attic temperature, the insulation's measured R-value could decrease by as much as 50%. 

To minimize these convection loops and their associated effects, some researchers suggest installing blown-in cellulose or a fiberglass blanket on top of the loose-fill fiberglass. Another solution is to purchase one of the currently available "convection blanket" products that can inhibit this convective heat loss. 

Cellulose and rockwool are more resistant to airflow than fiberglass because they are denser. They may also be more effective at reducing air leakage and associated heat loss, because their higher densities cause them to settle and seal more around rafters and in corners. 

Sprayed-in-place foam insulations are an alternative to loose fills in some applications. They offer higher R-values at lower thicknesses than loose fills and, when properly installed, can help stop air leakage. 

But no insulation, by itself, provides an effective air retarder because it cannot completely block airflow. Installing an air retarder along with your insulation and using caulking and weather-stripping seals all gaps and greatly reduces air infiltration into your home (see the section on Air Retarders that follows). 

Settling and Loss of Insulating Capacity: Many loose-fill insulations installed in attic cavities will lose some of their installed R-value over time because of settling. Cellulose loose fill settles more than rockwool or fiberglass loose fill-about 20% compared to roughly 2% to 4%. Therefore, install about 20% more blown-in cellulose insulation to offset this settling. Cellulose manufacturers are required by Federal law to state "settled thickness" on their bags. Because this can be confusing to consumers, many cellulose producers also specify "installed thickness" on their bags. Regardless, installed thickness can be estimated by adding 20% to the stated settled thickness, but be sure not to exceed previously mentioned weight limits. 

Researchers say that it is possible to install loose-fill insulations in wall cavities without settling. If the cavity is completely filled with insulation at the proper density, no significant settling should occur. A general density guideline for walls is roughly 3.5 pounds per cubic foot (17 kilograms per cubic meter) of wall cavity for cellulose and 1.5 pounds per cubic foot (7 kilograms per cubic meter) for fiber-glass or rockwool. These specifications are roughly twice the density of horizontal applications. 

One expert suggests this easy-to-follow guideline to ensure that wall cavities are being filled at a density sufficient to prevent settling. Use roughly one 30-pound (13-kilogram) bag of cellulose or about 15 pounds (8 kilograms) of fiberglass or rockwool for every three wall cavities you fill. (Assumptions: 8-foot [2.4-meter] walls, with 16-inch [41-centimeter] on center wall cavities, and 2x4-inch framing studs.) 

Fire Resistance: Loose-fill insulations offer very good resistance to fire. Although fiberglass and rockwool are naturally fire resistant, cellulose's fire resistance is achieved by adding chemicals. To ensure that it does not present a fire hazard, cellulose must pass tests established by the Consumer Product Safety Commission. 

Moisture Resistance: The average household generates a considerable amount of water vapor each day through activities such as cooking, laundry, and bathing. This vapor migrates into insulated cavities and, if it reaches the dew point (the air temperature at which water vapor cools enough to condense), it converts to liquid within the insulation. This reduces the insulation's effective R-value. 

All loose-fill insulations are permeable to water vapor. Permeability is the extent to which water vapor can pass through a given material. Fiberglass and rockwool absorb about 1% of their weight, and cellulose absorbs 5% to 20% of its weight. However, any insulation can absorb large amounts of water if exposed to extremely high humidity. 

Higher levels of outdoor moisture can also penetrate into insulated cavities. If your roof leaks, for example, moisture can accumulate in the attic cavity and wet the insulation to the point that it mats and compacts. Enough moisture penetration could even cause the ceiling to sag. 

If insulation is saturated only one time, it will eventually dry and regain most of its original R-value. However, loose-fill insulations that are repeatedly saturated will lose much of their R-value. Moisture also causes additional problems, such as mold and mildew growth. 

Before You Install Insulation: Upgrading or Repairing Other Building Components - There are other home weatherizing and sealing measures to complete before you undertake any insulation project. A tight, well-sealed home is more energy efficient and needs less insulation to keep you and your family comfortable. Tests have shown that far more cold air infiltration and heat loss result from improperly sealed windows, doors, ducts, light switches, and outlets than from insufficient insulation coverage or performance. 

Vapor Retarders: If you are adding insulation to an existing ceiling structure and a vapor retarder is not already installed, consider adding one. Generally, the vapor retarder should be placed on the warm-in-winter side of the insulation-usually the side facing the interior living space. However, in hot, humid climates (primarily the southeastern states), there is controversy over where a vapor retarder should be placed. No matter where you live, consult an insulation manufacturer and your building code official for recommendations on where to place a vapor retarder. 

When installing loose-fill insulations, a material such as 6-mil (0.006-inch, or 0.015-centimeter) polyethylene plastic sheeting can be used as a vapor retarder. Paints that act as vapor retarders are also available. These paints may be more practical for retrofitting homes where no vapor retarder exists because they can be installed without removing finished surfaces. 

Federal Housing Administration Minimum Property Standards require that any product, including paint, must have a permeability (perm) rating of 1.0 or lower to qualify as a vapor retarder. The lower the perm rating, the greater the material's resistance to vapor penetration. For example, 15-pound (6.8-kilogram) asphalt felt paper has a perm rating of 1.0, while 6-mil polyethylene sheeting is rated at 0.06, and common household aluminum foil is rated at 0.0001. 

If the drywall on your ceiling or wall is removed and the insulated area is completely exposed, you can install 6-mil polyethylene sheeting. Be sure that it runs continuously along the surface area of the ceiling and walls, and that no tears occur during installation. Additionally, all penetrations, such as electrical outlets and light switches, should be carefully sealed. There are preformed foam gaskets for use behind outlets and switch plates. 

Air Retarders: An air retarder reduces energy loss because it prevents heated or air-conditioned indoor air from escaping through the building shell. It also blocks drafts of hot or cold outside air-caused by winds and pressure differences between the inside and outside of the house-that reduce your home's comfort and heating or cooling efficiency. 

An air retarder is different from a vapor retarder in that it blocks only air, not moisture. The American Society for Testing and Materials specifies that a material must have a perm rating of 5.0 or higher to qualify as an air retarder. Remember, the higher the perm rating of a material, the more moisture can pass through it. An air retarder should have a high perm rating because this allows the escape of moisture that may have migrated into insulated cavities. In new construction, an air retarder (such as "house wrap" products that are now available) is often wrapped around the outside walls before installing the exterior finish, and a vapor retarder is installed around the inside walls before the interior finish is completed. 

Installation: Loose-fill insulations are typically installed with special equipment that blows the insulation through a hose and into the cavity. Although loose fills can be installed in both new and retrofit situations, they are especially popular for retrofit projects because they can be installed with minimal disturbances to existing finishes. 

Installation often calls for the "two-hole method," which entails drilling two holes spaced vertically between the exterior walls' framing studs. The holes should be 2 inches (5 centimeters) in diameter. Working between each stud, drill one hole 16 inches (41 centimeters) from the top of the wall. Drill the other hole 24 inches (61 centimeters) from the bottom of the wall. The insulation is blown into the holes, then the installation holes are sealed. Installation is most commonly done by professionals who are experienced at operating the equipment to ensure proper density and complete coverage. In conventional and cathedral ceilings, insulation is easier to blow in if an access opening through the ceiling already exists. Otherwise, it may be necessary to drill holes in the ceiling or between the roof rafters. 

Cost: At the time this publication was written, the average loose-fill insulation cost per R-value per square foot was about 0.8 cents for cellulose and rockwool and 1.1 cents for fiberglass. These prices were for materials only. The average installed price per R-value per square foot was about 1.2 cents for blown-in cellulose and rockwool and 1.3 cents for fiberglass. Because prices vary in different regions, obtain bids from several insulation contractors or suppliers to determine the specific cost in your area. 

Installation Quality Control: Voids and Gaps - To ensure a quality installation, there are several things to watch out for when installing loose-fill insulation-whether you do the job yourself or hire a professional. 

You may create undesirable voids or gaps if you install the insulation at too low a density or if you do not completely fill the cavity. Voids are most likely to occur at the top of wall cavities, above windows, around doorways, and in the corners of ceiling cavities. Voids also occur if the installation holes are improperly located between the vertical framing studs or if there are too few fill holes. Keep in mind, though, that installers' practices may vary regarding the number, location, and size of installation holes. 

It may be difficult to achieve recommended R-values with loose-fill insulation in the eave area of the attic. There are insulation techniques that can be used to insulate this area adequately. 

Fluffing: "Fluffing" occurs when insulation is installed to minimum thickness but not to minimum weight requirements. The result is a less dense application of insulation that requires fewer bags. When insulation is "fluffed," air passes more easily through it. This means increased heat loss. Additionally, the fluffed loose-fill insulation will eventually settle and result in a thinner layer with a lower overall R-value. Fiberglass is more "fluffable" than cellulose or rockwool. 

Intentional fluffing by unscrupulous contractors has been a problem in some parts of the country. To avoid these problems, compare bids from several contractors to see how many bags they specify. Count the number of bags used during installation, either by you or a contractor, and compare it to the instructions on the bag. The manufacturer should specify the amount of insulation required to obtain a particular R-value per square foot (or square meter) of space. 

Safety and Health Concerns: 
Safety Guidelines:
* Insulation blown into your ceiling cavities should cover the top plate of the wall, but be sure the eave vents are not covered. These vents provide necessary ventilation to your attic, and covering them could result in severe moisture problems. 
* Electrical devices and recessed lights (except "IC-rated" fixtures) require 3 inches (8 centimeters) of clearance from insulation. 
* Pipes for kitchen stoves, wood stoves, and furnaces should only be insulated with fiberglass or rockwool because cellulose may smolder if flue temperatures become hot enough. 

Health Considerations:
* Some observers contend that fiberglass particles can cause cancer if inhaled, and others state that the fire retardants and insecticides added to cellulose may be harmful to breathe. While the debate continues as to the health effects of loose-fill insulations, it is important to protect yourself when installing any type of insulation. Wear a quality respirator, and wear protective eyewear and clothing such as goggles, gloves, long-sleeved shirts, and pants to minimize contact with the insulation. 
* Insulation fibers can also be drawn into air distribution systems if the ducts are not properly sealed, allowing the fibers to circulate within the living space. Be sure to seal all of your home's ductwork, as well as any other openings where insulation could leak out of the wall or ceiling cavities and into your living space. 

Cellulose, fiberglass, and rockwool loose-fill insulations are good choices for many insulation projects. However, they are not suitable for all situations. Conduct careful research and consider factors such as your climate, building design, and budget when selecting the best insulation for your specific circumstances. If you control air leakage and ensure that the insulation you select is installed properly, you can reduce your energy bills and enjoy a more comfortable home. For information on insulation installation techniques and on other ways to weatherize, to select materials, and to make your home more energy efficient, contact EREC. 

Sprayed Fiber Insulation

Cellulose, fiberglass, and Rockwool (mineral wool) insulation products are typically installed as dry, blown-in loose insulation, and in the case of fiberglass and rockwool, as a rolls and batts. They are also available as "sprayed" products that are sprayed into place in building cavities. These used to be called "wet-sprayed insulation" because some water is generally used to activate an adhesive in the insulation so it will adhere to the building's components. The terms "sprayed" or "spray-in-place" insulation are now more widely used.

Sprayed insulation products have the advantage of completely filling voids in building cavities where rolled insulation types are difficult to cut and fit well. Since sprayed insulation tightly conforms and adheres to the building cavities, it reduces air infiltration and increases the insulation's effectiveness. It forms a uniform covering throughout the cavity and forms a good air seal between electrical wiring, pipes, framing members, and anything else inside the building cavity. Also there's little chance of the insulation settling since the insulation fibers adhere to each other and the sides of the building cavity. Poor fitting insulation yields poorer than expected insulation performance due to gaps in insulation coverage and random air movement within the insulation.

Cellulose is the most commonly sprayed insulation material used in residential buildings. A special blowing machine that combines water, an adhesive, the insulation (and a fire retardant in cellulose products) is used for applying the mixture to the building cavities. Once dry, it has an R-value of approximately 3.5 per inch of thickness, if installed at the product's recommended density. In addition to water and adhesive, a chemical fire retardant is also used in cellulose applications. The fire retardant can corrode metal fasteners, pipes, and other components that it comes in contact with. 

Fiberglass is the next most commonly sprayed material for residential buildings. Sprayed fiberglass application is commonly known as the Blow-In-Blanket System (BIBS). It uses roughly the same sort of equipment and adhesive that sprayed cellulose uses. However it doesn't prevent air infiltration as well as sprayed cellulose. The dried R-value is about 3 per inch of thickness. Fiberglass requires no additional fire retardant treatments. 

Rockwool insulation is most commonly used as fireproofing and thermal insulation in commercial and industrial buildings. It is seldom found in residential buildings. Rockwool yields approximately R-2.7 per inch of thickness.

There are some precautions to take when using sprayed fiber insulation. The chemical fire retardant within the products may corrode metal fasteners, pipes, or structural members that they contact. Unscrupulous installers can "fluff" blow-in-blanket insulation, installing it at lower density than disclosed to the homeowner. Excessive water content and insufficient drying may promote fungus growth inside building cavities.

Application and Cost: Sprayed insulation is most practical for new construction or unfinished spaces with exposed studs. Installations are often messy, since some of the insulation also adheres to unintended surfaces such as floors and windows. However, the adhesive binders are water-soluble so it is easily removed. After application, the stud edges are scraped clean with a special milling tool made for that purpose. As long as the "salvaged" insulation is free of debris it can be sent through the blowing machine again for reuse. 

Sprayed insulation also needs time to dry before being enclosed in the building cavity. Sealing a cavity too soon sometimes leads to fungus and moisture problems. The drying time for the insulation varies depending on the type of insulation material and its moisture content, the moisture content of the framing members, and conditions such as humidity and temperature. Applications may take two days to several weeks to dry completely. Two (proprietary) techniques for faster drying times is to use Rockwool, which does not easily absorb moisture, or netting over the studs to support the insulation, with less water content, as it dries.

Sprayed insulation systems cost more than fiberglass batt insulation. However, it generally is less expensive than sprayed foam, and performs almost as well in many cases. BIBS and sprayed cellulose are often comparable in price. Sprayed Rockwool may be less expensive, however it is often difficult to find installers for residences. Prices also vary with local supply and labor rates.