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Spray Foam 101 The good the bad and the reality!

Spray foam good or bad? Yes!


Confusing isn't it? Well lets see if we can take a bit of the mystery out, and add in some reality as well.


As someone who deals with spray foam on a regular basis I try to always give people who are considering installing it a bit of an education on what it is, how it works and what can potentially go wrong with an application.


First let me say that when properly applied closed cell spray foam (the only type that can be used in exterior walls in our northern climate ) spray foam is a fantastic product that has the highest R value per inch of any common insulation materials. It is a total and complete vapor barrier and will increase the strength of the building assemblies that is applied to. We will call this good foam.


Bad foam is what is known as off ratio foam and it can truly be a nightmare to deal with.

I will give you a quick overview of the process that takes a liquid resin to a cured foam in a matter of seconds and what can go wrong along the way.


The material comes in 2 separate 55 gal drums known as a set of foam. The A side drum is an MDI isocyanate resin that is also used to make gorilla glue and bowling balls. The B side drum is a catalyst to cure the resin and a blowing agent to make it expand. The blowing agent is a material that boils at approx 85 degrees.


Each drum has a pump that send an equal amount of each component to a reactor. The reactor heats the components to approx 130 degrees and pressurizes them to about 1000 psi. Leaving the reactor they each travel through a separate heated hose to maintain temperature until they reach the spray gun. When the trigger on the spray gun is pulled the 2 streams slam together with the force of 1000 psi and mix completely. The 130 degree blowing agent which boils at 85 degrees and is no longer pressurized boils violently causing a fairly thin coat of spray to expand up to 2 - 4 inches in height and curing in a matter of seconds to a high quality insulation product.


The things that can have a negative impact on foam quality is heat, pressure, humidity and ratio of components. For the most part heat and pressure are controlled by the reactor and rarely cause a major issue with foam quality. The issue that causes all of the horror stories about spray foam is off ratio foam. This is caused by inexperience, lack of maintenance, poor quality equipment or inattention while spraying.


If the foam goes off ratio and is heavy on the B side (curing/ blowing agent)) the foam becomes friable and is kind of soft and crunchy with texture like a Cheeto, not good but not the end of the world. However if the foam goes off ratio to be heavy on the A side ( resin) the resin will not cure and will give off amines that unfortunately smell like cat urine. If this improper mixture is not removed the amines can soak into building materials and be virtually impossible to remove. A skilled spray foamer can tell in a split second by the look of the material as it is applied if the foam has gone off ratio for any reason. Someone who does not notice this can create huge problems by continuing to spray off ratio foam that never cures and continues to produce foul odors until it and possibly the building materials are physically removed.

Spray foam is the only building material that is manufactured on site so it is incredibly important that you have a knowledgeable and experienced spray foam crew working on your project. All of Air Seal Techs spray foam crews have many, many years of experience to insure that you have a trouble and odor free spray foam experience.


At Air Seal Tech we are always happy to answer questions about any home performance issue or concern you may have.


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