On many of our quotes and proposals for a new roof system, an option is presented for ½” HD insulation. Oftentimes, the additional cost may be similar to upgrading to a thicker membrane or even upgrading to more insulation. So what is HD insulation, and is it worth the additional cost?

HD insulation is a stronger version of standard polyisocyanurate insulation, which is the most common type of insulation installed on flat roof systems. The difference is that standard polyisocyanurate insulation is 20 PSI, and HD polyisocyanurate insulation is 80 PSI to 120 PSI, depending on the type and manufacturer used. So, it is somewhere between 4 to 6 times stronger than standard insulation.

So why does the strength of the insulation, which is under the roof membrane, matter? It provides a stronger surface for the new roof system to be installed over, which helps reduce punctures and support the membrane overall. The best way to visualize this is to think of a piece of paper. If you try to write on it on a soft surface, or even no surface, the pen will go right through the paper. If you write on a solid surface, like a wooden desk, the paper doesn’t puncture. With HD insulation, it’s a similar concept. It’s harder to puncture or damage the roofing membrane if the underlying insulation has a stronger surface.

So, where is HD insulation strongly recommended? Most often on roofs with a lot of foot traffic. We typically recommend HD insulation on buildings with a lot of rooftop units, where people are regularly on the roof performing maintenance. Also, we strongly recommend HD insulation on roofs that are going to have solar installed. Solar roofs have a lot of foot traffic, both during and after the solar installation. Also, it’s a good idea to consider HD insulation on roofs near the water, where birds and other animals may be on the roof.

HD insulation is a good idea on just about any roof, but the additional cost means that it isn’t the right solution for everyone. Talk to your roofing contractor about it prior to awarding the project and look at some samples before deciding. Also, think about your existing roof system and how many leaks you have had as a result of holes and punctures. This can help justify whether or not the additional cost is worth it.

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