By: Chris Casey, Sales Representative – Architectural Products
As we all know, the building codes are changing, requiring more insulation for both walls and roof. One of the considerations that roofers in particular will have to keep in mind is the increased potential for much higher labor and material cost in order to comply with building codes. The reason for this is the limited 4 inch thickness of polyisocyanurate.
Example: R-30 Roof using Polyiso vs. EPS
If we were to take the published R-value of R-6 per inch, a roof would require two layers of 2.5″ Polysio (5″ in total) to meet the R-30. However; according to the NRCA, the actual in-service performance of Polyiso is closer to 4.8 per inch. Which means in order to achieve that same R-30, you would need 6.25″ to comply, rather than the published R-value thickness.
EPS achieves R-30 using 6.25″ of Type IX EPS roof insulation. It is always important to make sure that you are comparing apples-to-apples in terms of density. Type II Polyiso, which is the standard density used for roofing, is a 2lb density material. Type IX EPS is also a 2lb density. If you have the same amount of material (2lb) occupying the same amount of space (1 cu ft) with the same insulating medium (air), it stands to reason that the R-value will be the same.
The benefit of using EPS in this application is twofold. First it has a 100% thermal warranty for 20 years (polyiso has, at best, an 80% thermal warranty for 10 years). Second, the cost savings of EPS is roughly 25%.
Those material cost numbers do not even factor in labor cost savings. If there is a large section of taper insulation, it is quite common to have to stack several layers of Polyiso to achieve the desired slope. Further, to create a proper cricket or saddle, there is typically an excessive amount of hand cutting being done by the contractor on the roof, which adds significant labor cost.
By using EPS, the taper can be created with far fewer pieces because EPS can be manufactured up to 36″ thick. For the complex cricket, due to the ease of factory pre-fabrication, the pieces shipped to the jobsite do NOT require onsite fabrication. The contractor simply installs the pieces according to shop drawings and moves onto the next task.
The end result of using EPS is improved energy performance, lower material cost, and lower labor cost. Who wouldn’t want that?