Frequently Asked Questions

1. What does R-value mean?

R-value measures insulation’s resistance to heat flow. It can also be referred to as “thermal resistance.” The higher the R-value, the greater the insulating power. All materials having the same R-value, regardless of type, thickness, or weight, are equal in insulating power. The R-value of different insulating materials must be based on test methods established by the American Society of Testing and Materials (ASTM). Don’t forget that R-values are determined by material type, thickness, and installed weight per square foot, not by thickness alone. Insulation helps keep your home cool during the summer months and warm during the winter months.

2. How much insulation should my house have?

The U.S. Department of Energy recommends home insulation R-values based on where you live. See R-value recommendations for your climate zone.

Be sure your new home complies with current building code requirements for insulation. These building codes establish minimum levels of insulation for ceilings, walls, floors, and basements for new residential construction.

3. What is the difference among fiberglass, rock and slag wool, cellulose, and foam insulations?

Fiberglass is made from molten sand or recycled glass and other inorganic materials under highly controlled conditions. Fiberglass is produced in batt, blanket, and loose-fill forms.

Rock and slag wool are manufactured similarly to fiberglass, but use natural rock and blast furnace slag as its raw material. Typical forms are loose-fill, blanket, or board types.

Cellulose is a loose-fill made from paper to which flame retardants are added.

Foam insulations are available as rigid boards or foamed-in-place materials that can fill and seal blocks or building cavity spaces. Foams are also used in air sealing to fill gaps, cracks, or openings.

Reflective materials are fabricated from aluminum foils with a variety of backings such as polyethylene bubbles and plastic film. Reflective insulations retard the transfer of heat; they can be tested by the same methods as mass insulation and therefore assigned an R-value.

A Radiant Barrier is a building construction material consisting of a low emittance (normally 0.1 or less) surface (usually aluminum foil) bounded by an open air space. Radiant barriers are used for the sole purpose of limiting heat transfer by radiation.

4. Can insulation help reduce unwanted sound?

Yes. Insulation is an efficient way to reduce unwanted sound, and it is commonly used to provide a more comfortable and quieter interior environment. Insulation effectively reduces noise transmission through floors and through interior and exterior walls. A professional insulation contractor can help you select the proper insulation for your needs.

5. Where can I get more information about insulation?


6. Do I need to remove my old attic insulation before putting in new insulation?

No, but is helpful in remediating a pest infestation, cleaning up air quality and removing dust and other harmful materials that might affect air quality in a living space. In most cases, it is not detrimental to add new insulation on top of old, but it is most likely beneficial and could help improve indoor air quality.

7. How does spray foam work?

Spray foam is a two-part mixture of chemicals that expand rapidly and solidify to fill a cavity or void, completely and permanently, adhering to wood, metal, concrete, and other materials. Spray foam when applied properly by professionals is very effective because it offers both an air seal, and an insulation R-value (resistance to heat). Spray foam slows the transfer of heat or conditioned air.

8. Are there any other areas to insulate besides the exterior walls and attic?

Insulation can be installed in many different areas of your home. House wrap that goes on before the siding can even be considered a type of insulation. When installing new windows and doors, a lot of homeowners are unaware that before the siding goes on, the perimeter of the window or door should be insulated with 6-inch self-adhesive rubber flashing. It drastically stops drafts from entering the structure and prevents interior heating/cooling loss.

Other areas of the home that should be considered for insulation include:

  • Knee walls in living and attic spaces
  • Dormer ceilings
  • Sloped walls and ceilings
  • Around foundations and slabs
  • Between the foundation and bottom sill plates (exterior walls)
  • Vaulted or cathedral ceilings
  • Floors located above vented crawl spaces
  • Interior basement walls
  • Floors over unheated areas such as porches and garages
  • Inside box headers for windows and doors
  • Floors located above unheated basements
  • Interior walls – cracks and crevices around windows and doors before it’s trimmed and finished
  • Interior floors, ceilings, and walls where you desire sound-proofing