A common question we receive is what is the difference between Blue Board and Thermax™?
Officially Styrofoam™ Brand Extruded Polystyrene Foam Insulation, No wonder it’s commonly known as Blue Board
- Blue Board is an Extruded Polystyrene (XPS), its blue color is a trademark of the Dow Chemical Company. Other manufacturers make similar products but in other colors. Officially this product is trademarked as Styrofoam™ however Styrofoam has come to be used with a much larger range of expanded foam and extruded foam products. Somehow getting your coffee in an “expanded polystyrene” cup seems a bit wordy.
- Blue Board is available in a wide range of board styles, and thicknesses which share common characteristics. Being closed cell foam it makes a good insulator (typically R5 per inch) that is resistant to water damage and mold growth.
- Dow Styrofoam™ can be used below grade and Dow has specific products to channel water away from foundation walls.
- Blue Board is combustible and should not be used in living spaces without a thermal barrier (typically gypsum board [wall board]). Maximum use temperature is 165° F. This may be a consideration when using in high temperature areas.
- Most XPS has been said to be unfriendly to the environment due to the chemicals used in manufacture. Dow’s XPS products (Blue Board) are hydrochlorofluorcarbon free with zero ozone-depletion potential.
- Thermax™ Sheathing is a Polyisocyanurate (Polyiso) foam board infused with glass-fiber reinforcement. Polyiso boards are sandwiched between facer materials. In the case of Thermax™ these facers are 1.0 mil aluminum or a 1.0 mil white acrylic bonded to aluminum.
- Thermax™ is available in a range of board styles, and thicknesses. Polyisocyanurate (Polyiso) is also a closed cell foam which is more efficient per inch than blue board (R6.5 per inch). It is resistant to water damage and mold growth.
- The aluminum facers reflect back radiant heat in addition to foam insulation. This increases the heat savings over the rated R value.
- Thermax's™ fire rating allows it to be installed in interior spaces such as basements, attics and crawl spaces without an additional thermal barrier.
- White Finish Thermax™ offers a finished look without the need for additional covering or paint. White Finish Thermax™ has the exact same insulation properties as standard Thermax™ Sheathing.
- Polyiso insulation has a higher cost per square foot than XPS.
- A little more care in transportation and installation is needed than blue board and similar materials. Once installed the aluminum facers provide a durable easy to clean surface.
- Some sources claim Polyiso is not as efficient in frigid temperatures; exterior applications of Polyiso may not perform as rated in extreme cold. When installed in interior spaces this is not a problem and the full insulation value is not affected.
Dow Styrofoam™ Blue Board is a cost effective insulation that can be used in a wide variety of applications, including foundation walls, under siding and exterior sheathing, and between wall studs. Blue board needs to be covered with a thermal barrier on the inside or with siding or other covering to the outside.
Dow Thermax™ is a higher efficiency insulation that performs well in interior spaces. Since it doesn’t require a thermal barrier you can achieve a high R value without covering it and increasing wall thickness.