Energy Foam Insulators, a division of Craftsman Construction came across an article written by David B. South, that we believe is the definitive story about Spray Foam Insulation and the R value of fiberglass insulation. Below are several excerpts from the article Mr. South wrote.
It is impossible to define an insulation with a single number. It is imperative we know more than a single "R" number. So why do we allow the R-value fairy tale to be perpetuated? I don't know. I don't know if anybody knows. It obviously favors fiber insulation. Consider the R-value of an insulation after it has been submersed in water or with a 20 mile per hour wind blowing through it. Obviously the R-value of fiber insulations would go to zero. Under the same conditions, the solid insulations would be largely unaffected. Again R-value numbers are "funny" numbers. They are meaningless unless we know other characteristics.
The use of an R-value alone is absolutely ridiculous. Yet we have Code bodies mandating R-values of 20's or 30's or 40's. A fiber insulation having an R-value of 25 placed in a house, not properly sealed will allow the wind to blow through it as if there were no insulation. Maybe the R-value is accurate in the tested material in the lab, but it is not even remotely part of the real world. We must start asking for some additional dimensions to our insulation. We need to know its resistance to air penetration, to free water, and to vapor drive. What is the R-value after it is subjected to real world conditions?
What Mr. South is saying is that in order for fiberglass insulation to perform at its label rated R value, it needs to be meticulously installed in the home. In fact, fiberglass insulation is never installed in your house to the test standards that it is rated for. What this means is you are paying for R value that you will never receive.
The filter medium for most furnace filters is fiberglass -- the same spun fiberglass used as insulation. Fiberglass is used for an air filter because it has less impedance to the air flow, and it is cheap. In other words, the air flows through it very readily. It is ironic how we wrap our house in a furnace filter that will strain the bugs out of the wind as it blows through the house. There are tremendous air currents that blow through the walls of a typical home. As a demonstration, hold a lit candle near an electrical outlet on an outside wall when the wind is blowing. The average home with all its doors and windows closed has a combination of air leaks equal to the size of an open door. Even if we do a perfect job of installing the fiber insulation in our house and bring the air infiltration very close to zero from one side of the wall to the other, we still do not stop the air from moving through the insulation itself vertically both in the ceiling and the walls.
What Mr. South is stating here is that even if by some miracle the fiberglass batts were installed perfectly around every pipe and wire and was fitted into the stud cavity with the upmost precision in measuring and cutting, air will still move thru the fiberglass itself. It's this air infiltration that robs you of the R value you are paying for.
Mr. South goes on to state the following:
The only commonly used solid insulation that absolutely protects itself from air infiltration is the spray-in-place polyurethane. When it is properly placed between two studs or against the concrete block wall or wherever, the bonding of the spray plus the expansion of the material in place will effect a total seal. This total seal is almost impossible to overestimate.
In my opinion most of the heat loss in the walls of the home have to do with the seal rather than the insulation.
For physical reasons, heat does not conduct horizontally nearly as well as it does vertically. Therefore, if there were no insulation in the walls of the homes, but an absolute airtight seal, there would not necessarily be a huge difference in the heat loss. This would not be the case if the insulation was missing from the ceiling. Air infiltration can most effectively be stopped with spray-in-place polyurethane. It is the only material (properly applied) that will fill in the corners, the cripples, the double studs, bottom plates, top plates, etc. The R-value of a material is of no interest or consequence if air can get past it.
Craftsman Construction has been using Spray Polyurethane Foam (SPF) Insulation for over 10 years now. "We absolutely insist that our clients use this product to insulate their homes and business. We believe in this technology so much that 2 years ago we invested almost $100,000 to purchase the equipment necessary to install this product said Mr. Jackness, President Craftsman Construction."
To read the entire article by Mr. South go to http://www.craftsmanbuilds.com/and look it up in our article archives. It is very well written and will enlighten you to SPF insulation.
Mr. South is president of Monolithic. He holds several patents and has won many awards in the construction industry. He is also the author of The Polyurethane Foam Book, Dome Living and Think Round.