What Is Spray Attic Insulation?

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  • Written By: Lori Kilchermann
  • Edited By: Lauren Fritsky
  • Last Modified Date: 03 October 2019
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Spray attic insulation is a type of expanding foam that fills both cracks and crevasses, providing a very good barrier to heat escape and the entry of cold outside air. Unlike its cellulose predecessor, the foam-type spray attic insulation is applied in a thin layer and rapidly expands to nearly 100 times the original thickness. As the spray attic insulation dries or cures, it fills in air gaps between ceiling and wall studs to form a protective barrier that is designed to last a lifetime. Preparation work for this insulation is minimal, with care being required to avoid ruining the nailing face of any ceiling or wall lumber during application of the spray insulation product.

Attic insulation has been primarily installed as fiberglass bats or blown-in cellulose, which is nothing more than shredded newspaper. A foam-type of spray attic insulation has come on the market that is designed to be sprayed on as a wet liquid and applied in a very thin coat. As the insulation cures, it begins to expand to nearly 100 times the sprayed-on thickness. The foam goes into and seals air leaks between studs, roof boards and attic flooring, creating a virtually airtight seal against incoming and escaping air.


Thermodynamics show that warm air will be drawn into any area of cooler air, so any warm attic air will be drawn to the cooler, outside areas through the smallest of cracks and gaps. Some studies have shown that enough warm air escapes the average, uninsulated home to fill a hot air balloon daily in cold weather. The use of a quality, spray attic insulation can not only prevent this from occurring, it can also stop warm air from entering a cooler home in the summer months.

The preparation work for this type of insulation is minimal, with most effort commonly required in picking up objects that should not have insulation sprayed on them. Typical attic contents, such as storage boxes, trunks and other personal items, should be removed or covered prior to applying the insulation. Care must also be taken to avoid the nailing surfaces of any wall studs during application. The stud surfaces need to be kept free of the expanding foam because it will create a lumpy and uneven surface if a wall covering, such as paneling, is ever installed on the attic walls. In the event of an accidental application, the spray attic insulation can be trimmed off of the studs with a small hand saw or knife once it has dried.



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