Insulation materials are rated by their R-value (insulating power per inch of thickness). Insulation is also categorized by its water, chemical and moisture resistance.
Most insulation types are available as either foam board or loose-fill. The most popular options include fiberglass, mineral wool or cellulose. Other options include phenolic foam and spray foam.
Fiberglass
Fiberglass is one of the most common forms of insulation. It comes in rolled blanket-like insulation, known as fiberglass batts, or as loose-fill or blown-in insulation. It is a relatively inexpensive, fire-retardant material that helps to muffle sound and offers energy efficiency.
This type of insulation can be placed in walls, floors and ceilings, or in ducts and tank-style water heaters. It is usually installed between studs, joists and beams during construction. It is a good option for homes and commercial buildings.
It is made from melted glass fibers that are spun and coated with liquid binder and then broken into pieces that are allowed to cool. Some fiberglass manufacturers use up to 40% to 60% recycled glass in their products. In loose-fill applications, bagged fiberglass insulation is blown into place using an insulation-blowing machine.
This material is typically a little cheaper than other types of insulation, and it’s also easy to install. However, it’s important to note that the R-value of fiberglass varies widely and its performance is limited by convection, which can allow hot air to move around a home. It is also not waterproof, so it should never be used in a basement or crawl space. In addition, it releases particulates that can be harmful when disturbed, so anyone installing or removing it should wear gloves, long pants, a dust mask and a face shield.
Mineral Wool
Mineral wool, also known as rock wool, is a common insulation material made from rock, furnace slag from the iron industry and other raw materials. It comes in batt and board forms and offers good thermal resistance, fire resistance and acoustic performance.
Typically, mineral wool batts are unfaced—as opposed to fiberglass and cellulose insulation products that use a facer. Unfaced insulation tends to be less expensive than faced options. However, they can be a bit more difficult to install. The primary drawback is that unfaced mineral wool requires a lot of tacks to keep it in place, and the tacks leave a hole behind when removed. This is a problem in areas with outlets and other electrical components, where it can cause problems for homeowners down the road.
In addition, mineral wool can be prone to off-gassing of chemicals called volatile organic compounds (VOCs). Many manufacturers now use low or no VOC binders in their production processes, mitigating this problem.
Another disadvantage of mineral wool is that it has a lower R-value than fiberglass and can be more costly. It is more dense than fiberglass, so it weighs more and can be more challenging to handle during installation. It takes 3.5″ of mineral wool to reach R15, whereas polyiso only needs 2.5″. Polyiso is also more versatile in terms of installation, since it comes in rigid boards that can be cut to size during installation.
Cellulose
Cellulose insulation is made with shredded recycled newspaper and organic material such as sawdust, cotton, straw, hemp, or corncob. This cellulose is typically treated with boric acid, which increases fire resistance and makes it unattractive to pests. The resulting cellulose insulation is a very durable and effective product. It’s also hygroscopic, meaning it’ll dry out other materials in contact with it, and it won’t support the growth of mildew or mold.
It’s available as blown-in and batt insulation. Blown-in cellulose can achieve R-3.6 to R-3.8 per inch, which is better than fiberglass batts and most other cheaper insulation materials. However, reducing a home’s insulating value to a number alone doesn’t tell the whole story; it’s important to also consider other factors like air infiltration and convection, as these can lead to significant energy loss.
Because it’s a very dense material, cellulose is effective at filling gaps and corners and blocking unwanted airflow. However, it is not good at limiting heat loss through convection, and it is also relatively prone to settling after installation. This can reduce its R-value over time. It also requires specialized equipment to install, and it’s not as DIY-friendly as fiberglass insulation or even fiberglass batts. Cellulose is also flammable, and is a potential fire hazard, which may require the use of PBDE-based flame retardants in some homes.
Foam
Foam insulation is available in a wide range of density levels. Commercial grade rigid foam can have a density of 2-3 kg/m2. Some higher-density foam used as a structural core in boats has densities over 100 kg/m2. Rigid insulation can be cut with a fine saw or sliced and snapped like drywall using a utility knife. Foam is a clean, irritant-free product that can be handled with regular tools and does not require full suits of protective clothing or breathing equipment as fiberglass batts do. However, sprayed polyurethane foam must be sprayed very carefully in open wall cavities to avoid damaging the walls with overexpansion.
Spray-applied foams, such as open or closed cell spray foam and polyisocyanurate foam, can have a high R-value at a thin thickness. However, their R-values can decrease over time as the blowing agents leak out and air leaks in.
Expanded polystyrene (EPS), the most common rigid foam board insulation, uses a blowing agent called pentane. This hydrocarbon is not implicated in ozone depletion or global warming; however, the amount of oil used to manufacture EPS and other forms of foam plastic insulation contributes to fossil fuel consumption. Other types of insulating foam, such as polyurethane and polyisocyanurate, use chemicals called methylene diioscyanate and polyol, which are derived from petrochemicals. These materials may also contribute to global energy depletion and climate change.