Spray Foam and How It Can Improve the Residential Home
The use of expanding spray foam in the residential home is a relatively new innovation. Spray foam is the process of spraying two different chemicals through a spray gun system that is engineered to combine the two chemicals just prior to the spray nozzle. The chemical reaction of the two chemicals causes the spray material to expand and adhere to the surface being sprayed. There are two basic types of spray foam, closed cell and open cell.
The closed cell material does not expand as much as the open cell, however, the closed cell material is a vapor barrier within itself if it reaches a thickness of 2 inches. Therefore, with the use of a closed cell material, there is no need to apply a surface coating such as a vapor barrier paint on the surface. It is recommended that closed cell material be used in residential homes, it is more expensive than open cell, however, its use, eliminates the need for any type of vapor barrier and offers a more dense material, adding to the stiffness of the structure. If open cell material is used, although a better sound attenuation barrier, there will have to be a vapor barrier installed over the open cell foam.
There are various manufacturers of spray foam and this discussion will not compare one to the other. For this discussion the term spray foam will be used as a generic description of the material and the process. Each manufacturer will claim different characteristics and performance qualities of their foam products. It is recommended that the homeowner research the various insulation contractors in their vicinity and choose, according to recommendations and value.
The use of spray foam in the residential home;
1.) Spray foam is applied to the interior surface of the exterior sheathing. The spraying is conducted within the interior of the home once the entire exterior of the structure has been framed and sheathed.
2.) The application of the spray foam must be done in a somewhat controlled environment. Each manufacturer has a different specification for their application, but normally the temperature must be at least 40 degrees Fahrenheit. The building should be enclosed with windows and doors to prevent wind and rain from entering the structure. The roof should also be on the structure and at a minimum the building wrap installed. It is important that the building is watertight to prevent water to compromise the foam insulation.
3.) The spray foam should be applied to all the surfaces between the studs. This application will seal the openings in the exterior walls and will fill any voids in the framing. There is an expansion coefficient with this foam and areas of the framing may cause the actual spray foam to expand beyond the limits of the framing. If this is the case, the foam if open cell is easily scrapped or sawn away to eliminate any interference with interior sheetrock or sheathing. Care must be taken, however, if the closed foam material is being used. This is a much denser and harder material and it is more difficult to remove if it has expanded beyond the intended surfaces. This material must be chipped away and will take considerably more labor to accommodate overspray.
4.) In the attic and roof area, the decision must be made, whether to spray the underside of the top floor of the home or to spray the underside of the roof. The use of spray foam applied to the underside of the roof, will allow the use of the attic as a habitable space. Of course, if the attic is never intended to be used for this purpose, the spraying of the underside of the top floor will reduce the square footage of space requiring heating and cooling.
What are the benefits of spray foam insulation?
1.) Spray foam insulation offers a much higher insulation value, per inch of insulation, than either fiberglass batts or other types of insulation. The open cell will expand more than the closed cell, therefore obtaining the required thicknesses with less material. Again, however, the vapor barrier issue as well as the sound attenuation value of open foam should be considered in the discussion regarding which product to use.
2.) Open cell spray foam offers a much greater sound attenuation factor within the structure. The use of open cell spray foam causes the interior sound level to drop, due to the tremendous insulating value of the foam and its sound absorbing qualities. In addition, unlike other insulation methods, the foam application, leaves NO voids or cracks in the system. Therefore, there are no openings for sound to travel. As one homeowner along the shoreline indicated, I have to open my windows to listen to the surf. The entire home will feel more sufficient and stable without ambient exterior noise infiltration as well as interior creaking of any of the framework. Although open cell foam has a higher sound attenuation value, either of the foam products will stiffen the structure and fill the voids in framing, sheathing, etc. therefore, reducing sound transmission through open spaces.
3.) Spray foam stiffens the entire structure. Due to the inherent characteristics of spray foam, both in its adhesion capabilities as well as its dense properties, there is a structural stiffening of the structure, once the foam has been applied. This can increase the resistance of the structure to movement and stiffen the entire assembly regarding heavy wind and storms. This is especially important in tornado and hurricane prone areas. In fact, I have heard that the square foot, per inch costs, of spray foam in areas of tornado activity can be substantially higher than in normal weather locations.
4.) The use of spray foam under the first floor framing system, when there is an exposed lower level area, such as with a home on the beach is especially practical. The ability to spray the bottom side of the framing without the need for additional vapor barrier material, is especially important, due to the stiffening properties, the ability of the foam to sustain any weather related issues that would promote deterioration, and the level of insulation possible with spray foam. In addition the density of closed cell material in this location provides a strong and weather tight seal up against the structure. If this is the application and the bottom of the structure is capable of garaging vehicles, then the spray foam will have to be sheathed with a fire resistant covering of sheetrock, plaster or other fire proof material to achieve the proper fire code requirements.
What are the disadvantages of spray foam?
1.) The early development of spray foams involved various odors and lingering fumes, that caused individuals to shy away from the product. These negative characteristics of the system have been totally eliminated, and there is no issue with fumes or lingering residue.
2.) Any exposed spray foam will require a fire barrier to be applied. This can be accomplished with an intumescent paint application, which is a special coating that will expand upon fire and heat to protect the spray foam insulation, masonry or drywall. Normally, if the spray foam is located against the interior surface of the exterior sheathing then the standard drywall installed to create the interior partition wall will be adequate fire protection for the spray foam. If the location is an area that is the ceiling of a garage space or other one hour rated fire code area, then additional layers of fire code sheetrock maybe required.
3.) The cost of spray foam is more expensive than a fiberglass batt or a sprayed cellulose material.
Although the cost of spray foam is more expensive than conventional insulation, the added expense is well worth the additional money, due to all the positive aspects of the product. The ability to increase the stiffness of the structure, reduce the noise level within the structure, as well as provide a consistent and high level of insulation value, are all overriding factors that make the cost of the spray foam a positive investment.
The ability to actually spray the foam insulation in hard to reach areas, or between close framing members, makes the use of spray foam especially attractive during renovations and additions.
During the renovation of a home, or the construction of a new home, it is strongly recommended that the use of spray foam insulation be investigated and considered. This is a growing technology that will provide you with a tremendous opportunity to not only properly insulate your home, it will also provide many other positive contributions to the livability of the home.
Spray foam is the next advancement in insulation technology, and its use at the present time must be considered.