The five most common kinds of retrofit home insulation are: fiberglass, cellulous, reflective (radiant) barrier, foam, and mineral fiber (rock wool).

Fiberglass insulation

• Fiberglass is the most common home insulation in America for both new construction and retrofit with about 75% of the market.
• There is some controversy about the safety of toxic emissions (e.g. formaldehyde, HFAs & HCFCs) and the long-term health effects of breathing in very small particles from fiberglass insulation.
• Up to 20% of the American population has some level of allergy to Formaldehyde. Long term "outgasing" of several toxic chemicals from fiberglass may not be easily recognized as a significant cause of allergy problems, particularly with small children.
• Johns Manville makes fiberglass without formaldehyde. Fiberglass emits noxious fumes when burned and is not a fire retardant.
• Fiberglass requires a relatively high amount of energy to be produced. It takes about eight (8) times as much energy to make fiberglass as cellulous home insulation.
• Some other insulation products are much Greener because of their higher energy efficiency in manufacture.
• Fiberglass is competitive with Cellulous as a relatively inexpensive insulation. It can be purchased at any big box hardware store, from distributors, or online. Fiberglass insulation can be blown in or installed with batts.
• Many insulation contractors have done fiberglass insulation installation for years and strongly recommend it.

Cellulous insulation

• Cellulous home insulation claims to be "the greenest of the green" and is now about 10% of home insulation market.
• Cellulous has a high energy efficiency in its manufacture because it made from recycled newsprint and other paper.
• Cellulous home insulation is unattractive to insects and rodents. Major termite and pest control companies install cellulous home insulation to help control common pests. Like fiberglass it can support mold if it stays wet.
• Cellulous is treated with non-toxic and permanent fire retardants. It has a Class A Fire Rating from the National Fire Protection Assn. and is approved by all building codes.
• Cellulous home insulation has outstanding sound dampening qualities. It is much better than fiberglass at reducing airflow leakage.
• Cellulous is comparable in cost to fiberglass. Many brands are available online.
• Cellulous insulation has about 30% more energy conservation per inch of depth than fiberglass. Limited space is a common problem in achieving consistently good home energy efficiency.
• Insulation contractors generally blow it into attics and wall cavities as loose fill. Although they typically express a preference for one, many insulation contractors can install either fiberglass or cellulous.
• For more information: read Cellulose Insulation – A Smart Choice, an excellent article from the University of Massachusetts on comparing cellulous to fiberglass.

Radiant barrier insulation

Image courtesy NASA

• Radiant barrier insulation is a reflective surface that reflects heat. Often the radiant surface (aluminum foil) is backed by craft paper or bubble wrap material.
• Properly installed in the right circumstances radiant home insulation can be effective and provide an excellent energy conservation value. Sometimes it can be a good supplement to a standard home insulation. It is most useful in tropical and humid climates.
• Radiate home insulation does not qualify for most tax rebates or credits.
• Sellers making exaggerated energy conservation claims have adversely affected the reputation of radiant insulation. The pricing of installed radiant home insulation is wildly variable. Some insulation contractors specialize in radiant insulation installation.
• Moisture barrier issues must be carefully considered with radiant insulation. Serious damage to a structure can be caused from moisture accumulating over time in walls, ceilings, or floors. The resulting mold growth can cause significant health problems.
• Although it is commonly done, it is not recommended to put a radiant barrier directly on top of standard attic insulation. Moisture issues can develop and dust on the reflective surface will quickly and greatly reduce the energy efficiency of the insulation.
• Radiant home insulation products are very inexpensive and can be purchased from any large hardware store or online.
• Done correctly, for the right energy efficiency application, radiant barrier home insulation can be an excellent energy conservation value.
• For more information: read Radiant Barriers - a Question and Answer Primer, an excellent un-biased article on the energy efficiency of radiant barrier home insulation, from the Florida State Solar Energy Center website.

Foam insulation

• Foam home insulation is typically several times more expensive than fiberglass, cellulous, or rock wool. Foam is about 10% of the home insulation market.
• Foam can be the best energy conservation choice in extreme climates. It can provide a very high energy efficiency value (R Factor) in a limited space.
• Spray foam insulation is excellent for sealing cracks, holes, seams, etc. and eliminating air leaks.
• Foam can be sprayed as a retrofit on attic interiors and under floors. A good job requires a well-trained spray foam insulation contractor and is not recommended for DIY insulation installation.
• Insulation contractors can use foam to retrofit walls. Insulation installation is done by pumping the foam into wall cavities through small holes.
• A wide range of foam insulation products are available. Most are made from petroleum, but some now have a substantial percentage of soy ingredients. Long-term toxic emissions may be an issue for some products.
• Because of the wide range in foam insulation products and training required, it is important to check with three or more spray foam insulation contractors before deciding.

Mineral wool (rock wool)

• Widely used throughout Europe mineral wool is a less popular home insulation in America.
• Mineral wool does not emit harmful fumes or fibers, and is an excellent fire retardant barrier.
• Mineral wool has excellent sound dampening qualities and is un-attractive to rodents.
• It generally costs about 10% more than fiberglass or cellulous, and has an energy efficiency per inch of depth that is between cellulous and fiberglass.
• Mineral wool home insulation installation is done in batts or loose fill just like fiberglass and cellulous.
• It can be purchased at distributors, ordered through retailers like Home Depot, or purchased online.
• Rock wool is very energy consuming to produce. It is manufactured by melting rock and slag and spinning it into microfibers. This makes its total energy efficiency less than some competing home insulation products.
• Most mineral wool uses about 40% recycled material. Thermafiber is a brand that makes mineral wool home insulation with 90% recycled material.

Summary

• A good DIY insulation job requires learning what insulation products are best for your energy conservation needs and how the insulation installation should be done to gain maximum energy efficiency.
• Even a very basic understanding of energy conservation will help you confirm that your insulation installation was done right and that you really got the best insulation energy efficiency for your money.