Blanket Insulation Types
Blanket insulation is the most common and widely available type of insulation.
It comes in the form of batts or rolls. It consists of flexible fibers, most commonly fiberglass.
You also can find batts and rolls made from mineral (rock and slag), wool, plastic fibers, and natural fibers such as cotton and sheeps wool.
BATTS AND ROLLS are available in widths suited to standard spacing of wall studs, attic or floor joists.
BLANKET ROLLS can be hand-cut and trimmed to fit. They are available with or without facings. Manufacturers often attach a facing (such as kraft paper, foil-kraft paper, or vinyl) to act as a vapor retarder and/or air barrier.
BATTS are simply blankets pre-cut into 4 ft. or 8 ft. lengths. Widths are standard 16 in. or 24 in. on-center making these forms of insulation best for wood framing that uses the same dimensions between studs.
BATTS with a special flame-resistant facing are available in various widths for basement walls where the insulation will be left exposed. A facing also helps facilitate fastening during installation. However, it is recommended that you use unfaced batts if you are re-insulating over existing insulation.
Thicknesses include 3-1/2 ", 6-1/4", and 9-1/2", but a 1 " version is available for special applications like around sills and narrow spaces inside masonry walls. The R-value for each of these thicknesses varies with the material.
Standard fiberglass blankets and batts have a thermal resistance or R-value between R-2.9 and R-3.8 per inch of thickness.
High-performance (medium-density and high-density) fiberglass blankets and batts have R-values between R-3.7 and R-4.3 per inch of thickness. See the table below for an overview of these characteristics.
Fiberglass Batt Insulation Thickness and R-Values
3 1/2" Kraft R-11
3 1/2" Kraft R-13
3 1/2" (high density) Kraft R- 15
6" to 6 1/4" Kraft R-19
5 1/4" (high density) Kraft R-21
8" to 8 1/2" Unfaced R-25
8 1/2" (high density) Kraft R-30
9 1/2" (standard) Kraft R-30
12" Kraft R-38
*This table is for comparison only.
Determine actual thickness and R-value from manufacturer and/or local building supplier.
**NOTE: Blanket (batt or roll) insulation and installation usually costs less than other types of insulation.
How to Determine the Amount of Insulation You Need
First, measure the length and width of your attic.**
If you have different sections of attic, measure them separately.
Then multiply the attic length by the attic width.
If you do have more than one section in your attic, multiply them separately and add the numbers together.
For example: 40 ft. width X 50 ft. length = 2,000 sq. ft. of attic area.
This will give you the square feet of insulation you will need to buy.
Take this number with you when you purchase your insulation.
Each package of insulation will have written on it the number of square feet in each package.
Use this number to divide into the number of square feet of your attic area.
Then purchase that number of packages.
**Note: When measuring the attic area do not include the overhangs
because you will NOT be installing insulation in the overhangs.
An overhang is the roof area extending beyond the exterior walls of the attic.
The maximum thermal performance or R-value of blanket and batt insulation
depends heavily on proper installation.
Therefore, it is best to have it done professionally.
The following guidelines will help in finding the best certified installer:
Obtain written estimates from several contractors for the R-value you need.
Don't be surprised to find quoted prices for a given R-value to vary.
Ask contractors about ventilation in your home as well.
Ventilation is very important to the effectiveness of the insulation installed.
To evaluate batt installation, you can measure batt thickness and check for gaps between batts.
If you decide to install the insulation yourself,
carefully follow instructions and the necessary safety precautions.
For your information, there are two types of installation procedures.
Most often the insulation is installed between the studs.
Manufacturers generally recommend installing the insulation on the face of the studs.
The drawback of this method is that your drywall cannot be glued to the face of the studs,
thus you increase the chances of having nail pops.
*****PLEASE NOTE: The insulation manufacturer may offer additional instructions.
Also check your local building and fire codes.