Replies

1. GBA Editor
   Martin Holladay | Jul 29, 2011 11:07am | #1

   Arlis,
   Over a swimming pool, a SIP roof should be much more durable than a roof assembly insulated with fiberglass batts.

   However, a few caveats:
   1. I am not an expert in swimming pool enclosures.

   2. Your architect is suggesting that both OSB facings (inside and outside) of your SIP should be enclosed in an impermeable peel-and-stick product. (When you refer to Duraperm, I assume you are talking about Duraperm 20-mil peel-and-stick Air Barrier/Vapor Retarder.)

   If you go ahead with that plan, be absolutely sure that the peel-and-stick products are installed on a dry, sunny day when the exterior relative humidity is low and the SIPs are very dry. Whatever moisture that OSB has on the day the peel-and-stick is installed will be the same moisture level that the OSB has forever -- so if it starts out damp, it will always be damp.

   And if any moisture ever finds its way to the OSB due to a defect in a layer of peel-and-stick, then the OSB will certainly rot fast. But let's hope the SIPs never get wet.

2. GBA Editor
   Martin Holladay | Jul 31, 2011 05:16am | #2

   Further thoughts:

   A much better assembly would consist of a SIP roof with a peel-and-stick membrane on the underside, facing the pool, but no peel-and-stick on top. Pay attention to maintaining air barrier continuity where the roof meets the wall, because you don't want interior air to get access to the seams between the SIPs.

   Here's how to detail the top side: install a vapor-permeable roofing underlayment (for example, #30 asphalt felt), followed by 2x4s to create a ventilation channel from soffit to ridge. Then install plywood roof sheathing over the ventilation channel, followed by more asphalt felt and roofing. This assembly will be much safer than the one you proposed.

3. 
   Dovetail7442 | Aug 06, 2011 08:19pm | #3

   Where are you building? The climate in which you build will to a large degree determine the correct answer. Condensation is the enemy, and this can only be effectively controlled with aggressive ventilation strategies. We've enclosed pools with SIPs and the challenges aren't really any greater than any other enclosure method. Take care detailing the vapour barrier. Use the windows as a barometer: if they are "sweating" in a heating climate the indoor humidity is too high. Don't underestimate the cost of doing HVAC in an enclosed pool: the front and operating costs can be staggering. But doing it wrong is even more costly in the long run.
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