Photo of hands installing insulation inside a wall with a graphic representing money savings and the caption "affordable interior insulation"

You’re working on remodeling your home to make it more sustainable, but your budget is getting a little thin. You still want to proceed with insulating the interior walls, though. So are there any low-cost insulating materials you can use for the job?

Here are 6 of the most affordable interior insulation options:

  • Radiant barrier
  • Stone wool
  • Fiberglass batts
  • Blown-in cellulose
  • Rigid board
  • Spray foam

Each has advantages in different situations, and all of them are available for a reasonable price.

In this article, we’ll go over each type of insulation on the list above, including a brief explanation of how the insulation works as well as the information you really care about, what it costs. Keep reading to find out! 

6 Inexpensive Insulating Materials For Interior Walls

Radiant Barrier

Although it’s typically installed in an attic rather than walls, the first insulating material you might consider is a radiant barrier. This form of insulation is installed so it’s aimed at an air space. Since heat goes from warm to cooler spaces, radiant barrier insulation lessens this radiant heat gain.

Radiant energy comes from sunlight, which usually heats up the roof of your home. Conduction allows the heat to reach the attic. Soon, even the attic floor and ducts are affected. This makes your previously cool house warm up very quickly via the ceiling.

With a radiant barrier, less heat transfer can occur between the roof and the attic. According to Energy.gov, you could reduce your cooling costs by five to 10 percent with radiant barrier insulation, especially if you live in a warm part of the country such as Florida.

Stone Wool

Also known as mineral wool, stone wool wasn’t a popular insulating material for a long time, but more homeowners are gravitating towards it again. One reason is that its R-value is slightly higher than fiberglass, which we’ll talk about next. The R-value difference is 15 for stone wool and 11 to 13 for fiberglass batts.

Another reason homeowners like stone wool is that they can install it in their interior walls themselves. Mineral wool is nonabsorbent so that if it gets wet, it won’t become saturated with water. If a major leak occurred in your home, you wouldn’t have to worry about the insulation collapsing on top of all the other damage there’d be.  

Stone wool is also resistant to fire, so it won’t lose its shape if the worst happens and a fire occurs in your home. The structural integrity of stone wool could even help control the spread of the flames.

Photo of a man wearing gloves but no other special equipment installing stone wool insulation batts on an interior wall.
It’s possible to install stone wool batts yourself, making this insulation an affordable option.

Fiberglass Batts

You’re probably still comparing your options at this point, so let’s talk more about fiberglass batt insulation next. Fiberglass is good at capturing heat before it can spread to the cold parts of your home. That’s why fiberglass batts are often installed in attics, crawlspaces, basements, and interior walls.

Fiberglass itself is made of glass fibers with plastic. You should always wear gloves (and sleeves) when handling fiberglass if you’re doing a DIY insulation install. The glass within it can scrape up your bare skin.

Blown-in Cellulose

We’ve written about blown-in cellulose recently, comparing it to spray foam insulation. If you missed that post and you’re interested in either type of insulation for your interior walls, please go back and give the article a read.

We’ll recap blown-in cellulose for you here. Blown-in cellulose is made with recycled wood or plant fibers (usually newspaper). Besides your interior walls, you can also request this insulation in your attic. Installation requires the cellulose to be blown in via a nozzle.

It’s far easier to install blown-in cellulose when your home is still in the construction phase. If you want to do it later, a technician will have to drill a hole into your wall that’s big enough for the blower nozzle, then blow the insulation in the hole, and finally, patch it up.

Rigid Foam Boards

Another low-cost form of insulation we’d recommend is rigid boards. This sheathing is built from expanded polystyrene, extruded polystyrene, and polyisocyanurate. These three materials are known for their durability and insulating properties.

Rigid foam board insulation can plug gaps in the walls where moisture can accumulate, which can prevent the development of mold and mildew. Its R-value is somewhere between a 3 and a 5 and thus not very high.

Since it’s so inexpensive, though, you can combine rigid board with other forms of insulation to increase the R-value. 

Photo of several stacks of white pieces of rigid foam board insulation
Rigid foam boards are available in a variety of sizes and thicknesses to fit your project.

Spray Foam

The last type of insulation we want to talk about is spray foam. We again point you to the article that compared spray foam and blown-in cellulose per the link above, so we’ll keep it brief here.

Spray foam insulation can have open or closed cells. Open-cell insulation is soft and flexible to reach the areas of your home that you can’t get to with other types of insulation. Closed-cell insulation is much more rigid, making it akin to most of the insulating materials we’ve discussed in this post.

The R-value of closed-cell spray foam is better than open-cell at 7 per inch. In the same amount of space, open-cell spray foam insulation has an R-value of 3.8. That’s going to be reflected in the cost, as closed-cell spray foam is more expensive.

Conclusion

Insulating your interior walls doesn’t have to cost a fortune. The six insulating materials we talked about today are all considered reasonably priced. Each has its own pros and cons, so we recommend looking at more than just the cost in determining which type of insulation would best keep your home comfortable. Check out our Ultimate Guide to Insulation to learn more!

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