What Is Flash And Batt Insulation?

You have a home project that needs insulating. Somewhere along your research journey, you came across the term "flash and batt." Is this a new type of insulation? What is it made of? Why have you never heard of it before, and should you consider it?

South Central Services works with insulation professionally. We've insulated hundreds of homes with spray foam. As we work with customers, we are responsible for discussing their insulation choices and giving our professional opinion on the options available to them.

There is no shame in not knowing the term "flash and batt." Flash and batt insulation is a controversial method among contractors. This controversy may be one of the reasons you have yet to hear about flash and batt. South Central Services does not install traditional flash and batt insulation. This article does not aim to dissuade you from the method based on our reservations but to give factual information so you can form your own opinion.

By the end of this article, you will be able to carry on conversations with contractors about this insulation method. You will also have the necessary details to guide any additional research. Specifically, you will know:

• What flash and batt insulation is
• Why it’s called flash and batt
• How commonly flash and batt insulation is used
• How flash and batt insulation works
• Problems that can arise when using flash and batt insulation

What Is Flash And Batt Insulation?

Flash and batt insulation is a combination of spray foam insulation and batt insulation. Traditionally, flash and batt refers to one inch of closed cell spray foam and a layer of fiberglass batt. Unless specified, you can assume a combination of spray foam and fiberglass when reading about flash and batt.

To create flash and batt insulation, a layer of spray foam is installed in a wall cavity. After the foam has cured, fiberglass batts are nestled against the foam to complete the wall insulation.

Why Is It Called Flash And Batt?

The word "batt" refers to a batt of insulation, but where does the "flash" come from? When noting the thin layer of spray foam insulation, "flash" describes the shorter installation time and the small amount of product used to create flash and batt insulation.

Is Flash And Batt A Common Insulation Solution?

For homeowners looking to cut insulation costs without compromising performance, flash and batt is an attractive option. While fiberglass batts alone are a much more common insulation solution, some spray foam insulation contractors install flash and batt.

Flash and batt is not a widely accepted practice due to problems that can arise after installation. Geography and climate also play a role in whether contractors use the flash and batt method.

South Central Services does not install flash and batt insulation because the traditional one inch of spray foam is insufficient in our climate zone. We do offer hybrid systems similar to the flash and batt method. However, our installations use more closed cell spray foam, which solves flash and batt problems but also increases the cost.

How Does Flash And Batt Insulation Work?

Flash and batt insulation intends to give homeowners the best insulation performance at the least possible cost. Spray foam insulation is the highest-performing insulation product available but is also one of the most expensive. Fiberglass batts do not offer stellar performance, but they are much more affordable than spray foam.

The high performance of spray foam is attributed to its high R-value and its air-sealing ability. A layer of spray foam can boost the R-value of the wall insulation. This layer can also create an air barrier, which prevents heat loss through air leakage.

The idea of flash and batt insulation is to spend enough money on spray foam insulation to get those benefits. Instead of filling an entire wall cavity with expensive insulation, the remaining space is filled with a more economic insulator. The drawbacks of fiberglass batts can be lessened with the spray foam layer acting as a barrier.

In almost every case, the "flash" of flash and batt is closed cell spray foam. Closed cell is a more rigid insulation than open cell, and it offers a vapor barrier at two inches of depth. Closed cell also requires fewer inches to be installed to achieve an air barrier.

Are There Problems With Flash And Batt Insulation?

Flash and batt insulation is an excellent solution in theory. In practice, traditional flash and batt can face many issues. There are three main issues that flash and batt experiences in application.

1. Insulation gapping
2. Condensation issues
3. Faulty installation methods

Let's examine each of these concerns in more detail.

1. Traditional Flash And Batt Experiences Gaps With The Batt Of Insulation.

Spray foam insulation adheres to the substrate it is sprayed against, but fiberglass batts do not adhere. Adhesion is a critical difference between these insulation types and how they function. When the two are used together to create flash and batt, the fiberglass batts may pull away from the spray foam layer and create a gap.

In exterior walls, these gaps can cause serious energy efficiency problems and losses. The goal of the layer of spray foam is to create an air barrier. Any gap between the insulations makes an air pocket. The air leakage inefficiencies, which spray foam should have solved, come back into play.

2. Traditional Flash And Batt Creates Serious Condensation Issues.

Spray foam insulation is revered for its air-sealing capabilities, but closed cell spray foam also has vapor barrier capabilities. In flash and batt applications, closed cell spray foam is almost always the spray foam product of choice. Vapor barriers are tricky because their relevance varies by climate zone and weather patterns.

In our climate zone, Climate Zone 5, vapor barriers are often recommended for exterior walls. A vapor barrier is supposed to keep vapor out of wall assemblies. A properly installed vapor barrier ensures that if vapor does enter a wall assembly, it can also escape. If vapor becomes trapped, it will condense into liquid water and can cause many issues like mold and mildew.

Traditional flash and batt insulation only uses an inch of closed cell spray foam. At one inch depth, closed cell foam acts as an air barrier, but not a vapor barrier. We do not recommend traditional flash and batt insulation for these reasons. Homes in southern Pennsylvania tend to experience more extreme weather conditions during summer and winter, which means vapor barriers and where they are installed are essential considerations.

3. Traditional Flash And Batt Is A Faulty Installation Method.

Contractors who install flash and batt may claim that one inch of closed cell spray foam is enough before adding fiberglass batts on top. They may claim that they are saving you money by installing such a thin layer. However, one inch of closed cell spray foam is not dense enough to create a vapor barrier. In our service areas, one inch of closed cell spray foam is not enough.

If too little spray foam is installed, spending money on spray foam at all is a waste of money. You will not reap any benefits of the higher performing insulation.

For the flash and batt method to have a chance at success, a minimum of two inches of closed cell spray foam must be installed.

Even well-meaning contractors may install spray foam at too shallow of a depth. Contractors with excellent control of their spray gun will not spray a perfectly even layer of spray foam. In a flash and batt application, the thinnest area of application must still meet or exceed the minimum. The traditional flash and batt method has little room for error.

Is Flash And Batt Insulation A Good Option For My Project?

Opinions on flash and batt insulation vary widely. At South Central Services, we do not offer traditional flash and batt insulation. While we understand the theoretical benefits of the flash and batt method, our climate zone requires more spray foam than is traditionally installed. We do not recommend flash and batt insulation for homeowners in southern Pennsylvania, Maryland, Virginia, and West Virginia. Depending on what project needs insulation, a hybrid system may be better suited for your needs.

Some contractors offer traditional flash and batt insulation as an option. After doing your research, if you want to have flash and batt installed in your home, you can search for a spray foam contractor who will complete that. No matter what insulation you choose, we recommend working with a knowledgeable contractor who you can trust.

The Bottom Line About Flash And Batt Insulation

Flash and batt insulation is a method of insulating with spray foam and batt insulation. This method aims to provide "the best of both worlds" by offering the performance of spray foam at the cost of fiberglass. Traditional flash and batt works well in theory but can run into issues in real-life application. In Climate Zone 5, a one inch layer of closed cell spray foam is insufficient.

The complexity and potential problems of flash and batt make it a controversial method in the construction world. Traditional flash and batt is not an insulation option offered by every spray foam insulation contractor. Climate and weather conditions may play a role, and some contractors find this method risky.

Now that you know more about flash and batt insulation, your next step is to:

• Weigh the pros and cons of traditional flash and batt insulation
• Learn about the hybrid insulation system, an alternative to flash and batt
• Compare open cell and closed cell spray foam insulation costs for your project