Home Insulation Facts




Merely mentioning the word insulation conjures up the feeling of comfort and safety. Your home insulation should have the same effect along with the added benefit of lowering your heating/cooling costs.

To achieve the required home insulation results, check your insulation in the attic, ceilings and floors, crawl spaces, basements, and exterior walls to see if you currently have the right amount of insulation or R-value.

R-value is the thermal resistance rating of insulation, in other words, how well it resists heat flow. R-value depends on the type of material, its thickness and density. The higher the R-value, the better the insulation.

A few notes and tips about insulation:

  • Different insulation types can be used together. For example, you can install blown-in cellulose or loose fiber insulation on top of batt insulation.
  • Generally low density insulation should not be placed under higher density insulation, since it loses some of its R-value when compressed. One exception is in attics where the insulation is loose filled and allows air circulation through the walls causing cold to penetrate during very cold temperatures.

    In that case putting a higher density insulation on top. Also, placing R-19 insulation rated for 6 1/4 inches into a 5 1/2 inch wall cavity will decrease its insulation value.

  • Insulation does not retard heat transfer through joists or studs even though it is installed between them. Heat travels or conducts through the wood, or metal joists, studs, rafters, etc. (thermal bridging)similarly to an electric short circuit, creating an overall lower R-value in the wall. To combat this, cover the top of the joists with insulation and use insulative sheating in walls.
  • The Federal Trade Commission has very clear requirements for home insulation and its installation. READ labels carefully before installing any insulation, and ask any contractor to provide you with the label from EACH package of installation used - which will also let you know how much insulation was actually used for what price.

So, based on your location, how much insulation do you need? Below is the DOE recommended values for insulation:


Now, the types of home insulation:

  • Rolls and batt insulation - Often made of fiberglass or rock wool, and available in widths to fit in the spaces of walls, studs, attics, and floor joists. (2x4 framed walls can hold R13-R15, ad 2x6 walls can hold R19-R21)
  • Loose fill insulation - Cellulose, fiberglass, and rock wool blown in with special pneumatic equipment. Since the material can fit cavities, it's a good choice for areas that are hard to insulate.
  • Rigid Foam insulation - Foam boards that have about 1 1/2 to 2x higher insulation value per inch, so they are very effective in areas with limited insulating space.
  • Spray Foam insulation - This type of insulation comes in many varieties (closed and open cell) and is not only high in R-value per inch, but also effective in air-sealing.

    Those that come in foam spray cans are excellent options for window and door frames, etc. Open-celled foam allows water vapor to move through the material better than closed-cell foam, but generally has a lower R-value compared to closed-cell foams.

  • Reflective insulation - These are aluminum foils with a backing such as paper, plastic film, polyethylene bubbles, or cardboard. This type of insulation is usefule in reducing downward heat flow.

    Reflective systems are usually placed between roof rafters, floor joists, or wall studs.

  • Radiant barriers - This type of insulation reduces summer heat gain and winter heat loss. In new buildings, select foil-faced wood products for roof sheathing (installed with the foil facing down into the attic) or other locations. For existing buildings, fasten across the bottom of joists.


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