# DIY: Calculator for Blown-In Insulation

Blown-in insulation is most often found in attics. It is blown between the studs in the wall and between the joists along the floor. This type of insulation can have various R-values depending on how thickly the insulation is blown in. The R-value refers to the measure of thermal resistance. The higher the R-value, the better insulated the wall or floor will be. The first step when installing blown-in insulation is to determine how many bags will be needed. This can be accomplished by following a few simple steps.

## Step 1

Measure the entire area of the room in which the insulation will be installed. Run a tape measure across the first side of the room from one edge to the other and record the length. Measure from the floor to the ceiling and record the height. Multiply the height by the length to get the total square footage of the first side.

## Step 2

Run a tape measure across the other sides of the room and record the measurements for the height and length. Multiply the two together just like in the previous step. Add the measurements of all of the sides together to get the total square footage of the walls.

## Step 3

Measure the length and width of the floor and multiply the two together. Record the measurement of the width of the studs in the walls. Most studs will be 3 1/2 inches, while some may be 5 1/2 inches. Measure the width of the floor joists to determine how thick the insulation will need to be to cover the entire area.

## Step 4

Refer to an R-value chart to determine what R-value will be needed. To cover the walls at 3 1/2 inches, R-13 will be necessary, and to cover the joists, which are generally 7 1/2 inches, R-30 will be necessary. Look at bags of insulation from different manufacturers to determine how many will be needed based on your square footage numbers.

## Things You Will Need

- Tape measure
- Paper
- Pencil
- Calculator

## Tip

- The R-value of the insulation will depend on the width of the studs. For best results, the insulation should come out to the edge of the studs on the wall and the top of the joists along the floor.