It Is the Roofing Industry’s Responsibility to Help Clients Recognize the Importance of Roofing Insulation

In many cases, commercial roofing insulation is the most expensive component of a new roof assembly. Often, building owners do not understand how the insulation selection made today is really a long-term financial decision. The advice a roofing contractor provides to a building owner regarding insulation is critical to helping the building owner make the correct decision from a technical-roofing perspective and business-decision perspective. Many questions we typically hear from prospective low-slope commercial roofing clients revolve around the insulation to be utilized in their new roof system.

  • What is the best type of insulation?
  • How much insulation is most appropriate?
  • What are the advantages of certain types of insulation?

As with everything else in roofing, there is no “one size fits all” insulation solution. There are endless permutations of building use, geography, investment-time horizon, and other factors that can and should influence the amount and type of insulation used in roof systems. However, in most cases, we’ve found that polyisocyanurate insulation is the optimal insulation for a roof system.

Polyisocyanurate insulation provides a substrate for the waterproofing membrane and thermal resistance.

Polyisocyanurate insulation provides a substrate for the waterproofing membrane and thermal resistance.


From a purely technical roofing perspective, polyisocyanurate insulation in a low-slope roof assembly performs two basic functions. First, it provides a substrate for the waterproofing membrane. Second, the polyisocyanurate insulation provides thermal resistance.

There are all sorts of ancillary benefits and purposes for the polyisocyanurate insulation, but the primary function of the insulation is simply to provide the substrate for the roof system and to complete the thermal envelope on the top of the building.

Much like concrete work, or any other kind of construction for that matter, the performance of a roof system is 100 percent correlated to the substrate upon which it is placed. The math is simple: the better the substrate, the better the roof will perform.

The current industry standard for polyisocyanurate insulation comes with an organic facer and a published density of 20 psi. The standard polyisocyanurate insulation is the most widely specified and utilized insulation in the industry by a wide margin.

Standard polyisocyanurate insulation is widely used, frankly, because it works well. Polyisocyanurate provides several attributes that make it the first choice in most commercial roof assemblies.


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