Why does SPT (Sip Panel Technologies) use polyurethane rather than polystyrene?

SPT chooses to use   , BASF – The Chemical   Company  , polyurethane foam insulation instead of expanded polystyrene (EPS) for following reasons.

1.  Polyurethane is a far better insulator. SIP polyurethane foam as a panel core comparison has a stable R-value of R-7 per 2.5 cm of thickness, versus R-4 for EPS. This means that you can achieve R-28   with     11.4 cm walls. EPS-insulated walls would have to be nearly twice as thick to achieve the same R-value.

2. While the EPS is simply glued onto the substrates, injected polyurethane foam adheres and bonds to every surface (substrates, top-plates, splines, cam-locks, electrical boxes, etc.), and then becomes rigid. Polyurethane panels can withstand higher transverse (or flexural), racking loads and higher compression (or axial).

3. Polyurethane has better fire in a panel core comparison, flame, and smoke characteristics. Polyurethane does not melt at any temperature. It will withstand constant temperatures up to 82   degrees   Celsius and will not char up to 135-degrees Celsius.

4. PUR Fact: A strong and durable bond exists between foam and skins.  Heat and pressure created by the chemical reaction of the expanding polyurethane foam forces complete adhesion of the foam core to the skins. EPS is simply glued.