R-Value and Spray Polyurethane Foam

Spray foam insulation is an excellent solution to re-insulating your home. It is especially crucial for houses with lower R-value insulation, commonly occurring in older models of houses. For instance, 20-year-old houses (and older) most likely have deteriorated insulation.

But what is R-Value, and how does spray foam insulation work? In this guide, we cover everything you need to know about the R-value and spray polyurethane foam.

Principles of Heat Flow

Heat flow is determined by the three principles of conduction, convection, and radiation. To better understand how insulation works, we must first understand these principles.

Conduction describes heat flow through materials. For instance, the metal spoon you use to stir your coffee conducts heat from the cup to your hand.

On the other hand, convection describes heat flow through gases and liquids. While radiation describes heat that follows a solid path and absorbs energy.

How Insulation Slows Heat Flow

Insulation materials typically work to slow down conductive heat flow and convective heat flow in some cases. It controls the movement of heat in a way that evens out the overall temperature of your home.

The cold winter season draws heat away from usual areas where people crowd in. It instead travels to commonly colder parts of your house, such as the attic, garage, or basement.

On the opposite end, the hot summer season pulls heat into the opposite direction, right where most people confer. To avoid this, you must have a sound insulation system to control where the heat transfers.

R-Values and Spray Foam Insulation

R-values are the measurement of insulation’s resistance to conductive heat flow. High R-value means better insulation for the material, signaling its effectiveness. 

Spray foam insulation is one of the most effective, R-value-rich solutions to your insulation problems. It is a common choice for many residential and commercial construction projects.

Not only does it insulate effectively, but it also reduces any air leaks by filling up spaces and shapes quickly. There are two types of spray foam insulation, open-cell, and closed-cell.

Open-Cell Spray Foam Insulation

Open-cell spray foam insulation is more vapor permeable due to its low density. It is commonly found in ceilings, walls, and roofs. It is worth noting that when used in colder, unvented climates, the foam should be covered with something to delay vapor.

This type of spray foam insulation contains carbon dioxide or water, which acts as a blowing agent. It also has more organic-based materials rather than petrochemicals, which is always a plus.

Closed-Cell Spray Foam Insulation

On the other hand, closed-cell spray foam insulation gives off the highest R-value, even more than open-cell does. It is also proven to be much more effective than cellulose or fiberglass upon insulation. 

Closed-cell spray foam insulation is typically used underneath ceilings, roofs, walls, or slabs. Its industrial-strength capabilities help it prevent air leaks and completely block moisture and slow down vapor.


Spray foam insulation is one of the most cost-efficient solutions to insufficient home insulation. When you lose control of heat transfer in your home, you will attract unwanted cold spots and uneven house temperature.

Make your home warm (or cold, when you want it) with American Foam Experts. We provide effective home maintenance solutions, specializing in SPF applications. Contact us today.