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What are the Best Exterior Wall Insulation Options? Blog Feature
Amanda Emery

By: Amanda Emery on May 12th, 2021

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Adding insulation to your existing walls is the best way to tackle issues you’re experiencing with uncomfortable rooms and high heating and cooling costs.

The bigger question is, what are the best exterior wall insulation options? Honestly, it comes down to the amount of remodeling you want to do, how much you want to spend, and your overall expectations.

RetroFoam dealers have been insulating existing exterior walls with injection foam in homes across the U.S. for almost 20 years. Our contractors understand how the injection foam insulation we offer works and the pros and cons of other materials.

We are on a mission to help you make the best-educated decision for your wall insulation project. As part of that mission, below, we will discuss all of the options available to you depending on if your walls are existing or taken down to the studs, as well as what each has to offer.

Best Insulation for Open Exterior Walls

What is the best insulation for outside walls that are exposed and open?

There are a lot of factors at play here, and it all boils down to your expectations. Do you want the best, or are you looking for a cheaper option? Are energy efficiency and reducing your carbon footprint important to you? 

Let’s get into the nitty-gritty of open exterior wall insulation options.

Fiberglass Insulation

Fiberglass insulation is one of the options that is going to require tearing down your drywall.

The material is made up of extremely fine glass fibers and would be installed as batts or rolls in the stud cavities. While fiberglass does work to slow down the spread of hot and cold air, it still allows for air movement into and out of the home.

Fiberglass is a fairly inexpensive insulation option for your exterior walls, and you can install it yourself if you feel confident in your skills. The downside is that fiberglass is known to sag and shift over time, meaning it has an expiration date, and you’ll need to replace it eventually. This recurring cost, along with the cost of remodeling your walls and supplies required for the DIY project if you so choose, makes that cheaper option much more expensive.

Foam Board Insulation

Foam board insulation is another material that is going to require you to do it while you’re remodeling or if you don’t mind tearing out your drywall.

Foam boards are rigid panels made of either polystyrene, polyisocyanurate, or polyurethane. These boards are sold in various lengths, facings, and lengths to custom fit the wall cavities.

Unlike fiberglass, though, it’s one and done. You won’t need to replace the foam board once you install it or hire a contractor to put it in. One thing to note, you will want to make sure you seal around the seams of the boards, or you will still have a lot of air leakage.

Spray Foam Insulation

If you want to create an air seal that will help maintain a constant temperature in your home, spray foam is the way to go.

Spray foam insulation is an environmentally friendly option for open wall cavities. Depending on the manufacturer and the material, the spray foam is mixed with either water or a chemical agent. 

Open cell spray foam is usually what is recommended for residential projects. The foam expands and completely fills the cavity. Closed cell foam can be used but is better suited for exposed walls as it is more durable.

Either spray foam will stop air movement into and out of the walls, making the home more energy-efficient and comfortable.

Best Insulation for Enclosed Existing Walls

Maybe that remodel isn’t your thing and isn’t in the budget.

That’s okay because you can still add insulation without the need to tear your house apart.

Both blown-in cellulose and injection foam insulation can be installed from the outside of your home, so there’s no need to take down any drywall.

Let’s take a look at what both options have to offer.

Blown-In Cellulose Insulation

If a complete home remodel isn’t what you’re looking for, you can still add insulation without tearing your home apart.

Blown-in cellulose can be installed from the outside of your home. The installer will remove a row of siding, drill holes into the sheathing, and blown-in the cellulose. 

This method won’t require tearing your house apart, but it can make a mess.

Cellulose is made up of recycled newspaper or denim. Due to its consistency, when it’s blown-in, the dust from the material can get through vents and outlets, thus all over your home.

Cellulose also is known to shift and settle over time, meaning you could be left with gaps of no coverage.

Injection Foam Insulation

Injection foam insulation, like RetroFoam, is installed the same way as blown-in cellulose.

RetroFoam is a tripolymer based resin that makes the injection foam insulation when it’s mixed with a foaming agent and water. The material has the consistency of shaving cream, so it fills every nook and cranny when it’s injected into the wall.

The main thing that stands out with injection foam when compared to the other existing wall insulation options is that it is the only one that creates an air seal. This air seal keeps the air you pay to heat or cool inside where you want it while keeping the outside elements out.

This air seal will make your home more comfortable and energy-efficient.

The injection foam will also never need to be replaced or have anything added to it over time to ensure you maintain insulation coverage in your existing walls.

Choosing the Best Insulation for Outside Walls

So, what is the best insulation for outside walls?

Well, it really comes down to your expectations and budget.

If you want to create an air seal in your existing exterior walls without the need to remodel your home, then RetroFoam is the best option for your project. On the other hand, if you’re looking for a cheap option just to get something in the walls and you’re not as concerned about energy efficiency and overall comfort, then one of the other options would be best.

If you think RetroFoam is the right choice for your exterior wall insulation and want to learn more about how it works, check out the Learning Center on our website.

Related Articles

What is the Best Type of Insulation for Insulating Existing Walls? (Injection Foam vs. Blown-In Cellulose)

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Everything you need to know about buying RetroFoam insulation. The essential foam insulation buying guide.

About Amanda Emery

Amanda previously has worked as a breaking news and crime reporter, TV news producer, and editor. As a journalist, she has won several awards from The Society of Professional Journalists - Detroit Chapter and the Michigan Press Association. Amanda uses her experience as a journalist to write content that will help educate homeowners on foam insulation benefits. When Amanda isn’t writing, she’s spending time with her husband Chris, daughter Lilith-Maeve, and rescued huskies Danger and Wendigo. She also loves knitting, making art, and cooking.