January 3rd, 2009
Open Cell vs Closed Cell Foam
One of the most common questions people have once they start considering Spray Foam insulation is “Should I use Open or Closed Cell Foam”. International Insulation Contractors, Inc. Sprays both open and closed cell foams. The intent of this page is to give the reader some practical knowledge about the differences between the foams as well as links to additional resources for further investigation.
Open cell foams- what does this mean? In simple terms it means that the majority of the individual cell structures are “open” or “broken”. The benefit of a foam with open cells is that you get a superior insulating product over conventional insulations at a reasonable price. Open cell foams offers a greater ability to install when the target area is crowded with obstacles or has “bad access” meaning that the applicator is not able to be applied straight on the targeted substrate.
One area where open cell foams out perform closed cell foams is in sound deadening. Most sound travels through air movement. Both open and closed cell foams are air barriers and therefore good sound barriers. This means that both foams will do a good job of “blocking” or “deflecting” external noise from your buildings or other insulated spaces. Open cell foams however will in effect “absorb” the sound as does carpet, soft furniture and heavy drapes or tapestries.
Although open cell foams have a higher noise absorption than closed cell, open cell foams fall short compared to closed in R value and moisture Retention. Most open cell foams have a .5# cubic foot density. These foams have an R-Value around 3.5 per inch. Open cell foams can have up to a 1.2# cubic foot density which is an R-Value of around 5 per inch. Closed cell foams typically have an R-value of around 7 per inch. Open cell foams can and will take on moisture. Their unique cell structure will allow them to dry out thus regaining their insulating value diminished by the moisture; however the presence of the moisture is negative and could lead to mold growth. Thus when using open cell foams it is important to have properly installed weather resistant house wrap on the exterior of the building and a vapor retarder of .1 perms or less on the interior or warm side of the insulated space. We recommend using an approved vapor retardant primer paint. Most closed cell foams will meet a perm rating of .1 or less at or around 2″ of sprayed foam. This eliminates the need for a vapor retardant on the warm side of the insulated space and virtually eliminates the possibility of mold growth within the foam.
When to use Open Cell Foams?
Use open cell foams when cavity space allows for enough open cell foam to meet your desired R-Value and when your project budget does not allow for closed cell foams. Open cell is ideal for most sound dampening. IIC can and will bring both open and closed cell foams to your job site.
Closed Cell foams: Where as 90% or greater of the individual cells in open cell foams are open the inverse is true of closed cell foams. In closed cell foams the cells are filled with a gas that increases its insulating value. These closed structures also provides greater strength and stability then open cell foams. This closed “tight” structure prevents the passage of air, water and moisture vapors if applied thick enough, usually 2+ inches. This last quality of closed cell foam is often viewed as its greatest. Because moisture vapors will not pass though closed cell foam, mold spores can not grow for they need nutrients, oxygen, moisture and favorable temperatures Closed cell foams stave mold spores of all these needs with the exception of favorable temperatures Molds can not survive on this alone. See article on molds for more info. www.realtor.org/realtororg.nsf/pages/moldfaq