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How Much Insulation Do I Need? Facts & FAQs

Various types of insulation

As you’d probably guess, the amount of insulation you need largely depends on the size of the space you’re insulating. However, calculating the exact amount you need based on your space can be a bit challenging. The area is rarely perfectly rectangular or square, which can make it challenging to get an exact number.

Luckily, calculating close enough is not terribly difficult. You may not get exactly how much insulation you’ll need, but you’ll get closer enough for practical purposes.

There are several factors you’ll need to consider first, however. Different insulation requires different laying practices, for instance. Therefore, whether you’re using rolls of insulation or spray insulation has a huge effect on the amount of insulation you’ll need.

Where you live may also govern how much insulation you want to use. Mild areas will need less insulation than more extreme climates, for instance. Homes that are seeking to be close to carbon-neutral will probably want plenty of insulation, as well.

Generally speaking, after you figure out the thickness of the insulation you’ll need per square foot, you’ll need to find the area of the space you’re insulating. Basically, for a rectangular area, this involves multiplying the height by the length. That will give you the number of square feet you’re insulating, which you’ll then be able to multiply by the amount you need per square foot.

Rolls of insulation are very easy and do not need the added step at the end. Instead, just find the area of the wall you’re insulating and then purchase that. If there are any doors or windows, you can find their area and subtract it from the total, since you won’t be laying insulation on top of them.

divider 7 How Do I Calculate How Much Insulation I Need?

The math is rather simple when trying to calculate how much insulation you need. Here is a step-by-step guide to what we briefly explained above:

step-by-step guide
  • Determine the amount of insulation per square foot. If you use rolls, you won’t have to do this. Your climate and the type of insulation you’re using will largely determine the amount you need per square foot.
  • Next, determine the square footage of the wall. You can do this by multiplying the length by the height if it is a square or rectangle. For triangles, multiply the length and the height and then take half.
  • Finally, figure out the square footage of any doors and windows to subtract from your total.
  • Multiply this final answer by the amount of insulation you need per square foot. That will give you the amount of insulation you’ll need to purchase for your whole project.

You can also do this whole process in inches if it makes more sense to you. However, feet do work well for most situations. If your space has a bunch of nooks and crannies, you may not get an exact answer without doing a few more steps of math (which is often unnecessary). However, this will give you a close-enough answer that should get you through the project.

construction of house with structural insulation panels
Image By: Bilanol, Shutterstock

How Many Rolls of Insulation Do I Need for 1,000 Square Feet?

The depends largely on the size of each roll and the R-value of your location. The R-value determines how much insulation you need in your area per square foot and is based on the local climate. As you might expect, certain places need more insulation than others. Therefore, be sure to check the R-value before insulating your home.

Often, you can purchase rolls with different values. Therefore, simply find a roll that is the correct R-value and purchase 1,000 square feet of it. When using rolls, determining how much you need is much simpler, as you don’t have to do any extra calculations involving depth.

For instance, if one roll of insulation covers 100 feet, you’ll need 10 rolls to cover 1,000 feet.

Consult an insulation expert

Find an insulation specialist in your area, and get free, no-commitment estimates for your project.

Can You Put Too Much Insulation in a House?

Generally speaking, you can overdo the amount of insulation in a house. However, you have to really overdo it. The amount of insulation needed for a home depends on the location of that home, which is why finding your area’s R-value is important.

Usually, R values will have a minimum and a maximum amount of insulation you need per square foot. In colder areas, you’ll need the insulation laid on thicker than in warmer areas.

If you go over the maximum amount of insulation, you may end up with a home that is a bit too airtight. You do want some airflow between your home and the outside world. Otherwise, you can run into all sorts of problems.

For instance, your home’s air quality will plummet, as new air cannot get in. Indoor air is often much more polluted than outdoor air. Therefore, you do want some exchange occurring. Furthermore, moisture can also get stuck inside your home, which can lead to mold growth.

Therefore, while more insulation is often better, this is not always the case. You can go a bit too overboard in some instances.

man working on exposed wall with insulation
Image Credit: Bilanol, Shutterstock

How Much Insulation Do I Need Per Square Foot?

Once you know how much insulation you need per square foot, you can multiply that value by how many square feet you need to insulate. However, finding out how much insulation you need per square foot can be difficult. Luckily, when using rolls, this is much easier. You simply need to find a roll that is the R-value that you need and then purchase enough to fill the area that you need.

You do not usually need to double-up on rolls, as they make them in all sorts of different thicknesses. Simply purchase a roll that is suitable for your area.

Loose-fill insulation is a bit more complicated. Usually, most loose-fill insulation has an explanation of how much equals what R-value. This is the information you need to determine the thickness you need per square foot. Most loose-fill insulation has handy guides on the side of the package or online for determining how much you need based on the R-value of your area.

divider 7 Conclusion

Determining how much insulation you need can seem a bit overwhelming and complicated. However, it is actually quite simple.

Rolls of insulation are the easiest to determine. You simply need to find a roll that has the correct R-value and then get enough square feet to equal the square feet in the space. However, loose-fill insulation is a bit more complicated, since the amount you need will depend on your R-value.

Usually, loose insulation has a handy guide on the package that explains how much equals what R-value. You’ll need to determine the amount of loose insulation that equals the R-value you need per square foot. Then, multiply that much by the number of square feet you have to insulate.

Featured Image Credit: stockcreations, Shutterstock


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