Insulation 101

Spray Foam Insulation

Spray foam is the most technologically advancedinsulation material available.   Developed by Otto Bayer in the 1940’s, it was originally used for military purposes.  It started being used in the residential market in the 1980’s and has been gaining popularity in that field since.  

Spray foam is a spray applied liquid plastic that expands and adheres to the substrate. Unlike batt materials, this allows sprayfoam to properly fill all cavities and prevent gaps.  The major advantage spray foam insulation is the fact that they are one of the few products that prevent air movement passing through them.

There are different kinds of spray foam, open and closed cell.  The primary difference between these two is density.  

Open Cell Spray Foam Insulation

Open Cell spray foam is the less dense of the foam, with a density of .5 lbs per cubic foot.  It has an R-value of around 4 per inch.  Open cell is not a vapor barrier, meaning it does not completely stop moisture from passing through, but it is an air barrier which stops air movement.  At 5.5 inches it is enough to prevent air movement in a roof in order to prevent condensation and ice dams.  In addition to insulating, it is decent at deadening sound as well.  Open is significantly cheaper (about half the cost) when compared to closed cell.

Closed Cell Spray Foam

Closed cell is indeed the Rolls Royce of the insulation materials.  With a density of 2.0 pound per cubic foot, it has an R-value of around 7 per inch.  Closed cell is not as good at sound deadening as open cell, but it does add a lot of structural stability.  


 Cellulose is one of the oldest types of building insulation materials and has been made from numerous materials including cardboard, sawdust and hemp.   Modern day cellulose is made from recycled newspapers and treated to be fire, pest and mold resistant.   Cellulose has an R-value of approximately 3.8 per inch and is excellent at reducing sound.  At Caddis, we use cellulose mainly to fill existing wall cavities and to insulate attic floors.  Cellulose can be installed loosely, like on attic floors, or dense packed in existing cavities.  In order to prevent settling, dense pack cellulose must be installed at 3.5 inches per cubic foot.  Cellulose can be installed in new construction projects by first installing a netting to contain it prior to drywall install.

Cellulose is an excellentsound deadening material.   Like spray foam, it fills and forms to fit any sized and shaped cavity.  Dense pack cellulose is an air barrier while loose fill allows air infiltration.  For this reason, a proper attic insulation job includes air sealing all gaps and penetrations with foam insulation.  Cellulose is generally slightly less expensive than open cell foam.

Fiberglass Batt Insulation

Fiberglass batt insulation has historically been the most commonly insulation material installed in building in the US.  Fiberglas is made from molten glass and comes in a batt form cut to fit the cavity.  

 Fiberglass Batt insulation has an R-value of approximately 3.5 per inch, although there are dense batts with a higher R-value.   Gaps between the batts and the framing can cause air infiltration.  Also, the material itself is not a vapor or air barrier and allows air and moisture to pass through it.  For this reason, fiberlass batts installed in the exterior shell of a building need to be covered with a vapor barrier.  In New England this barrier needs to be installed facing the interior of the building.  Due to the air infiltration, fiberglass batts installed in a roof system, need to have proper venting to prevent ice dams and condensation.   Fiberglass Batts, while not as effective as cellulose or mineral wool, can be used for sound deadening as well. 

Mineral Wool Insulation

At Caddis Insulation we use mineral wool mostly for fireproofing and sound deadening.  We consider it one of the more effective products installed between framing members for reducing sound transmission through walls and floors.   We highly recommend installing mineral wool in bathroom and bedroom interior walls, and between floors.