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Should I Add Additional
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How Much Wall Insulation Do I Need?

Hi Itchy,

We've decided we're insulating our converted garage ourselves. I'm in charge of purchasing the materials and I don't know how to measure for wall insulation. Can you give me some advice?

Measuring walls for insulation is easy.

First measure the height and length of the walls. Multiply the two figures to obtain the square feet. Next measure window openings by the width and height and multiply to get the square footage. Subtract the total square footage of the windows from the total square feet of the walls.

Example:

Walls                        1200sf
Windows                    -200sf
Insulation Needed:      1000sf
 

Next measure the distance between the framing studs, usually it will be 15" but it may be 23" in some areas. This is important as wall insulation is sold in these widths and it will save you a lot of time cutting the fiberglass batts to fit the wall cavities.

Finally you need to know if your exterior walls are framed with 2X4" or 2X6" or maybe even 2X8". This is also important as it will tell you how much insulation you add to the walls, based on the thickness.
R-Value is based on the thickness of the insulation. If you had 2X4" framed walls, you could add R-11 or R-13 fiberglass batt insulation. If they were 2X6" you could add R-19.

OK, you've measured the walls for insulation and determined the R-Value needed and the width of the insulation. When you get to the home improvement store you'll see that the bags or rolls of insulating have a chart showing how many square feet the package will cover. Simply divide the total square feet of the walls to be insulated by the bag or roll coverage and that will tell you how much insulation you need to purchase.

Related Tips and Advice:

How To Measure Attics For Insulation
How Much Floor Insulation Do I Need?
How To Insulate Concrete Walls
How To Insulate Kneewalls
How To Blow Insulation Into Walls