FOAMETIX of Chattanooga

Why Retrofit

Why retrofit an existing home with spray polyurethane foam?

The vast majority of existing homes in the world are insulated with a air-use insulator ( fiberglass, cellulose ). They are expected to insulate our homes and buildings based on the assumption of dead air and only the principles of advection and convection (R-factor). The problem is that the forces working against the envelope of the building are much more powerful and diverse than the air use insulator can control. Let us take for instance the R-30 loose fill in most attics; it takes just a couple of hours for the radiant heat from the attic to build to 140 degrees and go completely through the R-30 and start heating up your house and running up you power bill, most especially if your HVAC system and ducts are in the attic. When the sun goes down and your house should be cooling off the air-use insulator is holding the heat in and therefore not allowing the house cool off for several hours.


Winter time is the time of year that conventional insulation really becomes a energy eater. When the air in a home is heated the house becomes a hot air balloon, even though it will not raise off the ground, all the same physics of lift apply. When you heat the air; it wants to rise and it passes through the loose fill or batt insulation in your attic flooring. When this happens it takes the temperature and moisture that has accumulated in the living envelope and moves into the attic. Because of the air mass expanding (static pressure) in the summer months, we have had to vent the attic to relieve the pressure outside instead of it pushing into the living area. These same vents allow the pressure, temperature, and moisture you just paid to have in your home to escape. When air leaves the vents in the roof, replacement air must come in, bringing in cold air to be re-heated (Air Loss/Air Gain).

In retro fitting an existing home you must look first at where your money will be most well spent. The roof area of a house consumes as much as 50% of the energy needed to heat and cool a home. The crawl space of a home can consume up to 30% and the walls, windows and doors the balance. By spraying closed cell polyurethane foam against the roof deck of the building you will stop all the radiant energy from entering the structure. If there is no radiant energy the is no expanding air mass. If there is no expanding air mass you do not need vents. By eliminating the vents, you have now stopped your heat rise loss in the winter months.


The roof area of a house should be the first area sprayed as it is the largest energy consumer of the envelope. The floor or crawl space should be next. We advise not trying to re-insulate walls as the payback on a 18% loss would be cost prohibitive and not practical.

When we heat and cool the air in our houses we are doing so because we don’t like what is going on out of doors. When we do this it puts the building envelope in direct opposition to the most powerful force on earth, the atmosphere. A good example of this is our old refrigerators that frosted up and had to be defrosted regularly. Because the moisture ( in the form of a gas ) went right through the polyethylene wrapped fiberglass ( 4” ) we knew it was an invisible force ( vapor drive )that was not only making the freezer frost up ,but reduce dramatically the efficiency of the entire refrigerator. In the early sixties we started putting 1½ inches of closed cell polyurethane foam in refrigerators and they not only became more efficient, but frost free as well. This force goes back and forth between hot and cold seasons not only infiltrating your walls and attic with moisture, but mold colonies as well.

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