POLYURETHANE vs POLYSTYRENE
The question often arises "what is the difference between Polyurethane and Polystyrene". The review below is a general comparison and does not necessarily represent a particular manufactures product.
There are five main differences that need to be evaluated:
- R-value. Urethane has an R-value of 7.0 to 7.5 per inch whereas styrene has an R-value of 3.5 to 4.0 per inch. The R-value for both materials may vary by the manufacture and density of the material.
- Chemical resistance. Urethane is resistant to damage caused by other chemicals. Styrene is subject to attack by petroleum-based solvents such as gasoline, many types of insect sprays and common glues such as "Liquid Nails". These problems normally will not effect a building unless there is an insect infestation that must be treated.
- Fire damage. Urethane is a thermal-set plastic and does not melt. It is not damaged until the temperature reaches 700 to 800 deg. and then it "chars". KC Panels uses urethane that has been treated with flame retardant and has been tested as a Class 1 foam. A Class 1 foam means that when burned, an external heat source is required to sustain combustion. If left on it’s own, the foam will self extinguish. Styrene on the other hand will soften and 190 to 220 deg and melt at temperatures of 240 to 300 deg. Many styrene products are also classified as Class 1 foam and will not sustain combustion, but melt at a very low temperature. There is a lot of debate as whether the Class 1 fires test should apply to Styrene.
- Dimensional Tolerance. Due to the manufacturing process, styrene panels have the opportunity to have tighter tolerances for thickness than urethane panels. Styrene cores are cut with a hot wire and then laminated to the skins. This cutting process should be very controlled. Urethane cores are injected molded into the skins. The expansion of urethane is very dependent upon temperature, humidity and other factors. This expansion process is more difficult to control resulting in some thickness variations.
- Foam cutting tools. When routing out the foam for modifications there is a difference in the two materials. Styrene can be cut out using a hot wire, because of the low melting point. Urethane can not be melted so must be mechanically removed. A special router is used for this purpose.
Reference: "Foam-core Panels & Building Systems" published by Energy Design Update.
There are two additional advantages provided by KC Panels:
- Connecting method. Most panel to panel connections require separate splines that must be installed and require 4 rows of nailing to attach. KC Panels have a connecting "tongue" that is factory installed, eliminating the need to install the splines. This connection system only requires 2 rows of nailing, reducing total install labor.
- Material waste. Panel material is sold by the square foot. The standard process is to make the panels full size and then cut or remove the material for the windows and other openings. This waste material is included in the total cost of the project. Because of the unique manufacturing process, KC Panels does not manufacture the "hole" that is cut out so there is no charge for that material. This difference can make as much as a $1,000 lower project cost on a single home.
CONCLUSION
Urethane panels provide a better value and greater safety protection to a building structure.