Insulation R Value Chart

Wednesday, February 06, 2013 2:54:00 PM

In this article, you'll learn

  • The importance of the quality of your home's insulation system.
  • How to calculate the R-value of you home and what the value means.
  • Insulation values based on location and heat type (helpful charts included).
  • Do you like you need an energy analysis conducted on your home? Let us help you determine your insulation needs.


Insulation for your home PhotoInsulation is one of the unsung heroes of the home. It is never seen and rarely does one think about it. While often overlooked, insulation is essential to a comfortable and energy efficient home. However, not all insulations are made the same. There are a number of different materials such as fiberglass and cellulose as well as a number of different forms such as batting and blown in.

The common denominator among varieties of insulation is the R-value. R-value is a measurement of thermal resistance and measures the ability of heat to transfer from one side of an object to another. As a benchmark, one inch of solid wood has an R-value of 1. In comparison, an inch of fiberglass insulation has an R-value of 3.14 and an inch of blown cellulose in an attic has an R-value of 3.21.

Along with knowing the R-value of a particular insulation, it is also important to calculate the R-value of a total system. For example, a wall with 3 ½” fiberglass batting (R-value of 11) may have an overall R-value of nearly 14 because of siding, sheathing and drywall. Try the R-value calculator available through Oak Ridge National Laboratory. Just keep in mind this calculator does not factor in drywall (R-value .45).

Finally, there is no set standard for insulation in an area. Several factors determine how much or how little insulation you need. These factors include your geographic location and type of heating system used. The chart below outlines the R-value recommendation for different areas in your home for the zones outlined by energystar.gov and the furnace heat source you have. The chart also gives common types of insulation and their R-value.

US Climate Zones Map

 

Insulation R-Values for Location, Heat Type & Area*
Location Heat Type Attic Wall  Floor Crawl Space Wall** Basement Wall
Zone 1 Natural Gas 38-49 13 13 13 11
Oil Furnace 38-49 13 13 13 11
Electric Furnace 38-49 13 13 13 11
Electric Baseboard 38-49 13 13 13 11
Heat Pump 38-49 13 13 13 11
LPG Furnace 38-49 13 13 13 11
Zone 2 Natural Gas 38 13 13-19 13 11
Oil Furnace 38 13 13-19 13-25 11
Electric Furnace 38-49 13 19-25 25 11
Electric Baseboard 38-49 13 13-25 13-25 11
Heat Pump 38 13 13-19 13 11
LPG Furnace 38-49 13 19-30 25 11
Zone 3 Natural Gas 30-38 13 13-19 13-25 11
Oil Furnace 38 13 13-19 13 11
Electric Furnace 38 13 13-19 13-25 11
Electric Baseboard 38 13 13-19 13 11
Heat Pump 30-38 13 13 13 11
LPG Furnace 38-49 13 13-30 13-25 11
Zone 4 Natural Gas 38-49 13 25-30 25 11
Oil Furnace 49 13 30 25 11
Electric Furnace 38-49 13 25-30 25 25
Electric Baseboard 49 13 30 25 11
Heat Pump 38-49 13 13-25 13-25 11
LPG Furnace 49 13 30 25 11-25
Zone 5 Natural Gas 38 13 25 25 11
Oil Furnace 49 13 30 25 11-15
Electric Furnace 49 13 30 25 25
Electric Baseboard 49 13 30 25 11
Heat Pump 38 13 30 25 11
LPG Furnace 49 13 30 25 25
Zone 6-8 Natural Gas 49 13 30 25 25
Oil Furnace 49 13 30 25 25
Electric Furnace 49 13 30 25 25
Electric Baseboard 49 13 30 25 25
Heat Pump 49 13 30 25 25
LPG Furnace 49 13 30 25 25

*Ranges resulted from the slection of two different zip codes within the same zone (i.e. Dover, DE and Chattanouga,TN for zone 4)
**Crawl space walls  that are vented or have moist problems should not be insulated.

R-value of Materials and Depths
Material R-value/in 3 1/2" 5 1/4" 10"  12" 15"
Fiberglass (batt) 3.14 10.99 16.485 31.4 37.68 47.1
Fiberglass blown (attic) 2.20 7.7 11.55 22 26.4 33
Fiberglass blown (wall) 3.20 11.2 16.8 32 38.4 48
Mineral Wool (batt) 3.14 10.99 16.485 31.4 37.68 47.1
Mineral Wool blown (attic) 3.10 10.85 16.275 31 37.2 46.5
Mineral Wool blown (wall) 3.03 10.605 15.9075 30.3 36.36 45.45
Cellulose blown (attic) 3.21 7.455 11.1825 21.3 25.56 31.95
Cellulose blown (wall) 3.70 12.95 19.425 37 44.4 55.5
Polystrene Board 4.00 14 21 40 48 60
Polyurethane Board 5.00 17.5 26.25 50 60 75
Polyisocyanurate (foil-faced) 7.20 25.2 37.8 72 86.4 108
Open Cell Spray Foam  3.60 12.6 18.9 36 43.2 54
Closed Cell Spray Foam 6.50 22.75 34.125 65 78 97.5