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Attic Spray Foam: Does It Make a High-Performing Home

It is well-known that spray foam insulation provides superior thermal control for residential and commercial applications. Spray foam in the attic is a simple way to improve your home’s energy efficiency. 

Drop ceilings and bulkheads, plumbing and electrical service penetrations, duct leaks, and duct penetrations are examples of unsealed areas in most existing homes. Spray foam can be used to create an airtight and insulating surface.

Let’s delve deeper into this topic to determine whether its application to the attic creates a high-performing home.

Difference Between Open-Cell and Closed-Cell Insulation

Spray foam with open and closed cells has different physical structures. This affects how well they perform in heat transfer and sound absorption. Evaluation of these differences requires an understanding of the formation of foam insulations. 

When two chemicals come in contact, they quickly expand to form foam insulation. The expansion produces bubbles. When the spray foam’s open cell bubbles burst, only the struts (the point at which two bubbles touch each other) remained. In contrast, the closed cell insulation’s bubbles do not pop, creating connected, closed pockets.

Understanding Issues That Can Occur

Roof Composition

The roof deck, a plywood layer, protects the rafters or trusses of your roof. The waterproofing membrane and, in most cases, an asphalt shingle covering are installed on top of the plywood. 

In the case of closed-cell spray foam, it can prevent moisture from the roof surface from entering the attic. Open-cell spray foam can slow the transfer of moisture into the attic. This allows it to accumulate in the porous wood and insulation materials or condense in cooler areas of the house. 

Spray foam is applied to the attic side of the framing and wood decking. It is crucial to keep the roof decking dry while installing it.

On a wet roof deck, installing closed-cell insulation, an exterior waterproofing membrane, and shingles can cause moisture to become trapped. It can lead to severe problems with permeable wood decking and framing. 

If open-cell insulation is used, moisture can migrate to locations with lower relative humidity, but if the attic is not ventilated or climate-controlled, it will stay there. Both possible outcomes are undesirable.

Solar Vapor Drive

Moisture under the shingles may evaporate when the sun warms the roof, driving it through the waterproofing membrane and into the roof deck. The decking and framing will eventually deteriorate if the underside of the roof deck is sealed with closed-cell insulation. This traps moisture inside the wood.

On the other hand, this moisture can enter the attic if the insulation is made of open-celled material. Excessive humidity and condensation may result in spaces that ought to be kept dry. The solar vapour drive humidity transfer from open cell insulation can be very high if the attic space is not ventilated.


If you aren’t circulating the air inside the attic space, there can be problems with either option. Temperature and humidity differentials can still occur inside the home with closed-cell insulation. If the moisture cannot get out through the insulation inside the house and builds up in the attic space, mould can become an issue.

By understanding this article, you might know whether it is good to spray foam your attic by choosing a type that fits best. It would be best to consult professionals to know which type you should choose to make a high-performing home.

If you need insulation solutions in Saskatoon, consult PolarTech Spray Foam immediately! We are experts in what type to apply, providing professional spray foam insulation installation and removal services. Get in touch with us now!

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