Home Insulation Information
A qualified home energy auditor will include an insulation check as a routine part of a whole-house energy audit. An energy audit will also help identify areas of your home that are in need of air sealing. (Before you insulate, you should make sure that your home is properly air sealed.)
The table below provides an overview of most of the available insulation forms, insulation materials, their installation methods, where they're applicable to install in a home, and their advantages.
Table 1. Types of Insulation |
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Form |
Insulation Materials |
Where Applicable |
Installation Method(s) |
Advantages |
Fiberglass |
Unfinished walls, including foundation walls, and floors and ceilings. |
Fitted between studs, joists, and beams. |
Do-it-yourself. |
|
Foam beads or liquid foam: Vermiculite or perlite pellets |
Unfinished walls, including foundation walls, for new construction or major renovations. |
Involves masonry skills. |
Autoclaved aerated concrete and autoclaved cellular concrete masonry units have 10 times the insulating value of conventional concrete. |
|
Unfinished walls, including foundation walls; |
Interior applications: must be covered with 1/2-inch gypsum board or other building-code approved material for fire safety. |
High insulating value for relatively little thickness. |
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Foam boards or foam blocks |
Unfinished walls, including foundation walls, for new construction. |
Installed as part of the building structure. |
Insulation is literally built into the home's walls, creating high thermal resistance. |
|
Enclosed existing wall or open new wall cavities; |
Blown into place using special equipment; sometimes poured in. |
Good for adding insulation to existing finished areas, irregularly shaped areas, and around obstructions. |
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Foil-faced kraft paper, plastic film, polyethylene bubbles, or cardboard |
Unfinished walls, ceilings, and floors. |
Foils, films, or papers: fitted between wood-frame studs, joists, and beams |
Do-it-yourself. |
|
Ducts in unconditioned spaces and other places requiring insulation that can withstand high temperatures. |
HVAC contractors fabricate the insulation into ducts either at their shops or at the job sites. |
Can withstand high temperatures. |
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Enclosed existing wall or open new wall cavities; |
Applied using small spray containers or in larger quantities as a pressure sprayed (foamed-in-place) product. |
Good for adding insulation to existing finished areas, irregularly shaped areas, and around obstructions. |
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Foam board or liquid foam insulation core |
Unfinished walls, ceilings, floors, and roofs for new construction. |
Builders connect them together to construct a house. |
SIP-built houses provide superior and uniform insulation compared to more traditional construction methods; they also take less time to build. |
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The R-Value of Insulation
An R-value indicates an insulation's resistance to heat flow. The higher the R-value, the greater the insulating effectiveness.
The R-value depends on the type of insulation and includes its material, thickness, and density. When calculating the R-value of a multilayered installation, add the R-values of the individual layers. Installing more insulation in your home increases the R-value and the resistance to heat flow.
The effectiveness of an insulation's resistance to heat flow also depends on how and where the insulation is installed. For example, insulation that is compressed will not provide its full rated R-value. The overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself because some heat flows around the insulation through the studs and joists. Therefore, it's important to properly install your insulation to achieve the maximum R-value.
The amount of insulation or R-value you'll need depends on your climate, type of heating and cooling system, and the section of the house you plan to insulate.
R-Value Table
Material |
R/ Inch |
|
Fiberglass Batt |
3.14-4.30 |
|
Fiberglass Blown (attic) |
2.20-4.30 |
|
Fiberglass Blown (wall) |
3.70-4.30 |
|
Rock Wool Batt |
3.14-4.00 |
|
Rock Wool Blown (attic) |
3.10-4.00 |
|
Rock Wool Blown (wall) |
3.10-4.00 |
|
Cellulose Blown (attic) |
3.13 |
|
Cellulose Blown (wall) |
3.70 |
|
Vermiculite |
2.13 |
|
Autoclaved Aerated Concrete |
1.05 |
|
Urea Terpolymer Foam |
4.48 |
|
Rigid Fiberglass (> 4lb/ft3) |
4.00 |
|
Expanded Polystyrene (beadboard) |
4.00 |
|
Extruded Polystyrene |
5.00 |
|
Polyurethane (foamed-in-place) |
6.25 |
|
Polyisocyanurate (foil-faced) |
7.20 |
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Energy Star recommended insulation levels
Zone |
Add Insulation to Attic |
Floor |
|
Uninsulated Attic |
Existing 3–4 Inches of Insulation |
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1 |
R30 to R49 |
R25 to R30 |
R13 |
2 |
R30 to R60 |
R25 to R38 |
R13 to R19 |
3 |
R30 to R60 |
R25 to R38 |
R19 to R25 |
4 |
R38 to R60 |
R38 |
R25 to R30 |
5 to 8 |
R49 to R60 |
R38 to R49 |
R25 to R30 |
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