Polyiso insulation is a rigid foam insulation board commonly used in commercial and low-slope roofing assemblies. It is also commonly used in tapered insulation systems, where boards of different thicknesses help create slope for drainage.
Why It Matters
In low-slope roofing, insulation is part of the roof assembly. It can affect thermal performance, drainage design, membrane support, and code compliance. When drainage needs improvement, custom tapered polyiso layouts may be planned and ordered to direct water toward drains, scuppers, gutters, or roof edges.
Common Problems
Common issues include wet insulation, crushed boards, poor fastening, missing cover board where needed, ponding water, unclear roof assembly thickness, and assuming flat insulation boards can solve drainage problems without a tapered design.
Building Codes & Industry Standards
Polyiso insulation should follow roofing manufacturer requirements, local code, fire requirements, energy requirements, and the specific roof assembly design.
Exterior Echelon Notes
Exterior Echelon reviews insulation in low-slope roof assemblies because performance depends on the full system, not only the visible membrane. When polyiso is used as part of a tapered insulation layout, the slope plan and drainage targets matter as much as the insulation material itself.
