Island Flat Roofing Standard

In the middle of 2013, Rhode Island’s “R” value requirements for new flat roof systems changed from a minimum of 20 to a minimum of 25. As before, this only applies to instances where the existing roof system is removed, not situations where a new roof is installed over an existing roof. While many building inspectors in Rhode Island are not yet enforcing the new minimum “R” value requirements, as time marches on, it will become more and more common. And, Massachusetts is talking about enacting the same requirements state wide. To make things more confusing, beginning in 2014, the “R” value of polyisocyanurate insulation, the most common form of rigid insulation used in flat roofing, was decreased due to new testing standards. With the “R” value of insulation going down and the minimum “R” value going up, a decent amount of insulation will need to be added to the roof assembly. Prior to January 1st, 2014, 1 layer of 4” polyisocyanurate insulation was required to meet an “R” value of 25 or 2 layers of 2.1” to achieve the same “R” value. After January 1, 2014, 1 layer of 4.25” polyisocyanurate insulation will be required to meet an “R” value of 25 or 2 layers of 2.2”. Compared to the old minimum “R” value of 20 under the old testing methods, which required 3.3” insulation or 2 layers of 1.7” insulation, the insulation will be roughly 1” higher on both the single layer and double layer insulation assembly. This means more wood nailer and longer metal along the roof perimeter. Additionally, any rooftop units that were sitting low to the ground may need to be raised up. However, with a greater “R” value also comes greater energy efficiency in your building. With less heat, air conditioning, and other forms of energy leaving your building, you should see a reduction in your utilities and maintenance bill. Whether the amount saved will be enough to offset the amount spent is something we will only find out over time.

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