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Pros and Cons of Spray Foam Insulation

Pros and Cons of Spray Foam Insulation

Spray foam insulation is not new to the construction scene. It has been around for over 40 years and has become quite popular among homebuilders in the past 10 -1 5 years. This is likely because new technologies have improved the product greatly and it is extremely easy to apply. 

Homeowners like spray foam insulation because they can expect lower energy costs and benefits from improved heating and cooling.

But, is spray foam insulation all it’s cracked up to be?

How does insulation work?

First, it’s important to understand how insulation works. 

Insulation controls the transfer of energy from one place to another inside your home. This is achieved through the control of three mechanisms: conduction, convection, and radiation.

Conduction is how heat moves through or along a material in gases, liquids, or solids. Using a low-conductivity gas in insulation reduces the conductivity of the material. 

Convection only occurs in gases or liquids. When the molecules that make up these liquids or gases heat up, their density changes and becomes less dense. Therefore, the warm air rises and essentially escapes.

The type of material used in insulation may inhibit convection. For example, closed cell insulation with small cell sizes may inhibit air molecules from escaping or inhibit convection. This is exactly what a homeowner would want to happen.

Radiation is a method of heat transfer from one surface to another as energy. Radiation can occur in gases, liquids, or solids. Factors that affect radiation include the distance between surfaces, the temperature of the surfaces, and how shiny a surface is (or its ability to reflect thermal radiation). 

Thermal radiation is designed to restrict these three mechanisms and control how much heat is lost or gained. 

What are R-values of Insulation?

In the context of insulation, R-values measure how well insulation resists the conductive flow of heat. The R stands for resistance. After all, this is the actual point of insulation – to resist the flow of heat in a space. 

The R-value of the insulation tells you how heat-resistant the material is. The pockets of gas or air in the insulation determine how much heat will pass through and how quickly the heat will pass. 

Naturally, you would want insulation with a higher heat resistance (or R-value), but it’s not that simple. For example, if you have unlimited space between walls, the size of the insulation would not matter. Many homes, however, are built in a way that limits the amount of insulation that can fit between walls. 

If the goal is to maximize the amount of R-value your home has, then it behooves the builder to use insulation with the greatest amount of R-value. As we know, the space between walls, especially hard to reach spaces, does not always allow for the insulation with the greatest amount of R-value.

Is spray foam insulation the solution to a better, tighter home?

After reading some of our thoughts on spray foam insulation, you can decide for yourself if the pros outweigh the cons. 

What Is Spray Foam Insulation?

Spray foam insulation arrives on a worksite as a liquid and is manufactured immediately before application. It is a combination of synthetic materials that are fed through a hose.  

Once applied to a surface as a liquid, it expands 30 – 60 times its liquid volume. 

The spray foam adheres to walls, floors, and ceiling cavities and inhibits air movement.

There are three common types of rigid foam insulation: 

1. Expanded polystyrene (EPS) is known as beadboard. It has an R-value of 3.6 to 4.0 per inch. It is the least expensive and not as air-tight as the other two types. 

2. Extruded polystyrene (XPS) is used more often under slabs, foundation walls, or basement walls. It has an R-value of 4.5 to 5.0. 

3. Polyisocyanurate (Polyiso) performs in a less typical manner than other types of insulation. Even with a higher R-value, it tends to perform worse as the temperature gets colder. 

Pros and Cons of Spray Foam Insulation 


  • More cost effective by reducing energy consumption
  • Protects a home from water damage 
  • Fills cracks and holes 
  • Reduces the amount of allergens or pollen that gets trapped in a home
  • Prevents bugs and critters from easily entering a space
  • Prevents moisture from entering walls – potentially lowering the chances for mold growth 
  • Lasts longer than fiberglass insulation and does not sag 
  • Could provide additional structural support inside the home (although it is not intended to be a structural support)
  • Does not lose its r-value 
  • Fast and easy to install 


  • More expensive than other methods of insulation 
  • Not recommended to be a structural support outside the home 
  • Requires experience and knowledge of the product for safe and accurate application 
  • Occasionally gaps can form in the walls 
  • Foam needs to be mixed correctly to avoid exposure to gas (otherwise the product is safe once it is cured) 

In the quest to balance the cost of heating and cooling, is spray foam insulation the right choice for your home?