Spray Foam R Value

Spray Foam R Value

If you’ve never looked into or don’t have any experience with insulation, then you have probably never heard of R-Value. However, before you make any decisions for your insulation needs, you will need to know what R-Value is and why it matters. More importantly, you need to understand why it matters that spray foam insulation R-Value is the best in the insulation industry.

What is R-Value?

When it comes to spray foam insulation your home, R-value matters. Without getting too technical, the effectiveness of insulation is measured in R-value.

R-Value is a measurement of an insulation material’s thermal resistance. The higher the R-value, the more effective the insulation in preventing heat transfer. So spray foam insulation R-Value can directly affect the efficiency and comfort of your home.

the bottom line on spray foam r-value

The bottom line on R-Values

Since the R-Values of polyurethane spray foam insulation are so much higher than the other insulation options, spray foam insulation is the better option when compared to any other type of insulation for reducing air leakage. According to greenbuildingadvisor.com, closed-cell spray foam insulation provides an R-value per inch of 6.5, compared to other insulation types such as cellulose and fiberglass, with R-values of only about 3.5 to 3.7, making it the “king” of insulations.

Different types of spray foam insulation

When talking about the R-Values of polyurethane spray foam insulation, there are two types that you will come across, closed-cell spray foam and open-cell spray foam.

Closed-cell spray foam

With an R-Value of up to R-6.8 per inch, closed-cell spray foam insulation is the highest R-value insulation material available, and its air-tight seal decreases air loss, moisture buildup, and termite damage.

It also strengthens the structure of the home significantly where applied. This superior R-Value makes closed-cell spray foam insulation ideal for sealing crawl spaces and other outdoor environments.

open cell vs closed cell r-value

Open-cell spray foam

On the other hand, open-cell spray foam insulation’s unique texture – a property of its tiny, interconnected bubbles – provides an R-Value between R-3.5 and R-4 per inch. That means that your home will experience improved temperature consistency after spray foam has been installed. This will help reduce the cost of heating and even cooling your home.

In addition to insulating, open-cell spray foam insulation also seals cracks and crevices that allow the passage of air through your home.

This makes open-cell spray foam insulation especially valuable in attic encapsulation where high temperatures in the summer force hot air through gaps around light fixtures, joints, and air ducts. That hot air doesn’t just affect your comfort. It also distributes dust, mold, and other allergens from the attic throughout the rest of your home.

How long does spray foam R-value last?

Some may question whether the R-Values of polyurethane spray foam insulation diminish over time. Many industry studies suggest that the answer is brief, yes… followed by a comforting and long-lasting no.

When first installed, the R-value of closed-cell spray foam insulation is actually about 10 for a one-inch thickness. Overtime (around six months typically), it will drop to 6.5, then stabilize and retain its still-way-higher-than-all-other-insulations R-Value of 6.5 for decades.

Industry experts suggest that other types of insulation, especially those that can absorb moisture and “mat down” can suffer huge and permanent (up to 50%) R-value loss over time.

R-value measures an insulation's ability to resist heat flow.

Is closed-cell spray foam the only way to go?

Of course, closed-cell may not be the best choice for Louisiana attic insulation, since it would make detection of leaks impossible should they occur. In such cases, open-cell spray foam, with a density of .05 per square inch, would be a better choice.

Sunlight typically recommends 5.5″-7.5″ depending on the application. Both closed and spray polyurethane foam insulate and act as an air barrier keeping your home comfortable and reducing heating and cooling costs for the life of your home.

How spray foam insulation R-Value compares to other insulations

When comparing the spray foam insulation R-Value with other materials such as fiberglass or cellulose, an air seal is the key to success.

The truth is that neither cellulose or fiberglass can stop air. R-Value is a measure of heat transfer via conduction. This is good news for fibrous materials.

The benefits of air seal foam insulation

It all comes down to how heat travels.

Convection and air movement are more efficient than conduction at transporting heat. Here is where the air seal comes in.

Fiberglass and cellulose allow air to pass through them, but foam insulation blocks it.

It is almost as important to have an Air Seal than a conductive Resistance. Without stopping heat transfer, you are also stopping air movement.

choose the right spray foam insulation contractor

Another insulation value to consider

But remember, in addition to R-value, you should also consider a little something that you could call “C-value”. The “C-value” is the value of your contractor! As with any type of insulation, the product is only as good as its installer. Sunlight Contractors have a proven reputation for consistently excellent professional results – with hundreds of five-star reviews.


No other energy solutions provider can offer the savings and services that Sunlight Contractor does. From evaluations and estimates to energy conservation and production, we’re your one-stop-shop for energy efficiency with fair spray foam insulation costs.

Call or email Sunlight Contractors today to learn more about which spray foam insulation products will work best for you. Sunlight Contractors not only offers products with the best R-value — but you always get the best “C-value” too!

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