By: Nick Harvill, Sales Representative
I recently had an Architect ask me why should they use Foam-Control® PLUS+® Tapered EPS to slope their roofs rather than Polyiso? My answer was, “Why wouldn’t you use EPS?”
It has been proven by multiple agencies that Polyiso does not meet its published R-Value and the In-Service R-value of Polyiso is actually between 4.6 and 5.0, at 40 degrees mean temperature, even when it is new. Tapered Foam-Control® PLUS+® 150 is R- 4.6 and Foam-Control® 130 is R- 4.3 per inch.
Tapered EPS can be installed in one layer, eliminating hundreds of squares of application and gluing. It can be installed over a base layer of EPS roof insulation or Polyiso and a cover board on top. A three layer system.
The main purpose of the tapered insulation is to provide slope. Tapered roofing insulation can do that for 30% or more reduced cost per unit compared to Polyiso. EPS has the lowest cost per R-value of any rigid insulation.
Since the R-value of tapered EPS roof insulation is actually very close to that of Polyiso’s in-service R-value, the R-value tradeoff is minimal or none. So there really is no advantage to using Polyiso for the tapered layer and it costs more.