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Thermal Barrier vs Ignition Barrier: What’s the Difference?

new home insulation

Thermal Barrier vs Ignition Barrier: What’s the Difference? Blog Feature
Amanda Ringler

By: Amanda Ringler on January 9th, 2019

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Trying to understand insulation and building codes can be difficult if you are well versed in the industry, and can even be a little dicey for the seasoned pro.

One thing that often gets confusing for people building their new home or remodeling their existing home is the difference between ignition and thermal barriers and why they need one or the other when using spray foam. So, what are they and why are they so important when it comes to the construction of a home?

RetroFoam of Michigan understands what a home needs to meet code, especially when it comes to keeping your home safe in case of a fire. That’s where the ignition barrier and thermal barrier come into play.

We understand that reading through the building code is a daunting task, so we are going to give you the definition of both and what the differences are.

RELATED: What is Building Science? (Definition/Fundamentals/Importance)

What is an Ignition Barrier?

An ignition barrier is made to provide protection in a home by stopping a perceived hazardous material from igniting.

What this means is the ignition barrier provides protection from fire in areas where spray foam insulation is installed where entry to the space is limited, like in the attic or crawl space.

Most premium open cell spray foams have an ignition barrier built right into them. These spray foams have a Class One Fire Rating, which means they have a smoke development that is less than 450 and a flame spread index that is 25 or less.

When choosing your spray foam, it’s important to find a brand that has that ignition barrier built right into it.

What is a Thermal Barrier?

A thermal barrier is a physical barrier that is placed between spray foam insulation and the interior living space.

The thermal barrier is used mostly as a fire resistance measure. The building code hasn’t quite caught up with the innovations made with premium spray foams, so while they have that Class One Fire Rating they still have to be separated.

The materials that can be used as a thermal barrier are drywall, plywood, gypsum board, as well as DC-315 paint.

What’s the Difference Between Thermal and Ignition Barriers?

The difference between a thermal barrier and ignition barrier is pretty simple.

An ignition barrier is a material that has been added to make the insulation unable to ignite. A thermal barrier is a physical object that separates the insulation from a living space and protects against fire.

Next up is whether the spray foam needs to be covered or not with both barriers.

Spray foam can be left exposed without a thermal barrier only if the insulation has an ignition barrier built into it and only in certain areas of the home.

Even if the spray foam being installed in your home has an ignition barrier it will still need to be covered by a thermal barrier to separate it from the living space. Areas like the attic and crawl space, which aren’t part of the living space, can be left uncovered.

If the spray foam has no ignition barrier built in or applied, no matter what area of the home it’s in, it has to be covered by a thermal barrier.

Learn More About Insulation Code

Now that you know the difference between a thermal barrier and an ignition barrier when it comes to your insulation, you might still have more questions about the Insulation Code.

Doing a little research can go a long way, and making sure you are armed with knowledge before you start your project can be a huge help.

If you live in Michigan and you want to make sure your project meets code, check out our article on insulation requirements.

Ultimate Foam Insulation Buying Guide for New Build Homes

About Amanda Ringler

Amanda previously has worked as a breaking news and crime reporter, TV news producer, and editor in Flint and Detroit. Throughout her career as a journalist, she has won several awards from The Society of Professional Journalists - Detroit Chapter and the Michigan Press Association. As part of the RetroFoam of Michigan family, Amanda uses her experience as a journalist to write content that will help educate homeowners on the benefits of foam insulation. When Amanda isn’t writing, she’s spending time with her husband and rescued huskies. She also loves knitting, making art, cooking, and hosting dinner and a movie night for friends and family.