What Is The R-Value Of Spray Foam Insulation?

If you are building a new home, upgrading the one you already have or looking to save on your energy bills, or looking to upgrade a shop, shed, or pole barn on your property, then the chances are pretty that you are looking for options for insulation.

If your home was built sometime before the mid 1980’s or the insulation in your home was installed more than two decades ago, it’s pretty likely that you need to upgrade your insulation or have it replaced entirely. 

In your search for insulation contractors in Spokane you may have learned about polyurethane spray foam insulation. If you’ve been reading about spray foam anywhere on the internet you’ve also likely been informed that it’s the best performing insulation material out there. The top performance of spray foam as an insulator comes mostly down to one factor: a higher R-value compared to other materials.

To truly understand why spray foam is the superior insulation product, you need to fully understand what the R-value is and how insulation really works.

How Does Insulation Work?

The basic function of insulation is to slow down the transfer of energy, which in this case presents as heat energy. There are three ways in which heat energy can be transferred.

The first is through conduction – this is when heat moves from an area of high energy to low energy to low energy. A simple example would be to think about when you put a pan on a stove. The stove is hot and conducts heat to the pan until the pan is also hot.

The second is through convection – this happens when warm air or water in a container (or in the atmosphere) rises and the cooler air or water sinks. This process repeats until the air or water mixes and becomes an even temperature.

The third way heat energy moves is through radiation – this is the transfer of energy that warms you up when you go out in the hot summer sun.

Most insulation materials work primarily by slowing down the process of conduction, and certain materials are better or worse at doing this. The ability of a material to slow the transfer of heat energy can be measured. The results of these tests are measured in units called the Resistance Value, or R-value for short.

R-Value Of Spray Foam Insulation

When compared to all other commonly used insulation materials, spray foam boasts the highest R-value. This means that it transfers heat energy slowly and therefore insulates better. Materials that have a lower R-value are less effective insulators.

Aside from simply conducting the transfer of heat energy more slowly, there are additional properties that make spray foam such an effective insulation material. One of them is its ability to fill gaps, cracks, nooks and crannies – meaning that it slows conduction and convection. Another is the fact that, unlike cellulose or fiberglass, if it gets wet it will not lose any of its insulation power.

To understand the R-value of spray foam, you first need to understand that there are two types:

Open-Cell Spray Foam

Open-cell spray foam is the kind that is most often found in DIY kits you might be likely to find at your local hardware store. It is lightweight, pliable, and easy to work with. 

It’s called open-cell foam because of its internal structure. When the chemicals react to produce the foam, tiny bubbles are formed inside. These bubbles then burst,  leaving behind struts of foam only in the spots where the bubbles were initially touching.. This is why it’s so lightweight, it’s full of air! These air pockets are also the reason why open-cell foam is permeable to water.

Open-cell foam is 75% less dense than closed-cell spray foam. This leaves it with an R-value of approximately 3.8 per inch. It is effective against the transfer of heat energy, but unlike closed-cell foam, it will not lock out moisture.

Closed-Cell Spray Foam

The structure of closed-cell spray foam is similar to open-cell, except that after the two chemicals mix to form the insulation foam the tiny bubbles within do not rupture, forming pockets of air that are trapped within the foam for its lifetime.

Due to the differences in its internal structure, closed-cell spray foam is much more dense, much more rigid, and can act as a very effective vapor barrier – meaning it has the ability to completely block water and water vapor. Closed-cell spray foam has almost double the R-value of open-cell foam at around 7 per inch.

How Many Inches Of Spray Foam Do You Need?

You’ll have noticed by now that the R-value of an insulation material is measured per inch. This is referring to the depth or thickness of the material after it has been installed. How much spray foam insulation you need depends on where you live, which part of the home it’s being installed in, and which type of foam you are using – open or closed-cell.

Here in Spokane and North Idaho, due to the colder winter climate, most building codes require closed cell insulation.

As a general guideline, 4-5 inches of closed-cell spray foam is recommended for use on the ceiling or roof deck, while 2-3 inches should be used within the exterior walls.

Is Spray Foam Insulation Right For My Home?

The answer is almost unequivocally yes! Spray foam is the most robust and effective insulation material in existence! Besides being the most excellent insulation material money can buy, it also boasts many other benefits besides simply slowing the rate of thermal conduction. 

If you are thinking about installing spray foam insulation in your home, business, or pole barn, give us a call to discuss your project.