Replies

1. GBA Editor
   Martin Holladay | Oct 15, 2015 03:54pm | #1

   Jordan,
   You forgot to tell us your location or climate zone.

   You may want to read this article: Air sealing SIP seams.

   You certainly want to include interior tape on the SIP seams, as well as spray foam at the seams. Note that the installation of interior tape is tricky when seams occur over beams and rafters.

   The risk of a rotting SIP roof is certainly greater in cold climates than in hot climates. I would advise any cold-climate builder who installs a SIP roof to include ventilation channels above the SIPs in order to create a cold roof.

2. 
   jordangarrow | Oct 15, 2015 03:58pm | #2

   Martin,

   Thanks for your answer. I live in Western New York so Climate zone 5 or 6. I'm right on the border.

   Are the systems to ventilate that don't require essentially a second roof? I read about grooved SIPS but I haven't seen them anywhere.

3. GBA Editor
   Martin Holladay | Oct 15, 2015 04:04pm | #3

   Jordan,
   I'm not sure what you mean by "a second roof."

   Ventilation channels are usually created by installing 2x4s on the flat. Depending on what type of metal roofing you choose, the metal roofing can be installed on 2x4s, 24 inches on center.

   The easiest way to do this is to install the 2x4s parallel to the eave. You end up with a cold air space between the roofing and the roofing underlayment, but you don't end up with soffit-to-ridge airflow. Still, this approach works.

   If you want traditional soffit-to-ridge venting, you need two layers of 2x4s, installed in a cross-hatch pattern -- the first layer perpendicular to the eaves, and the second layer parallel to the eaves.

   What I'm saying is that you probably don't need to install plywood or OSB roof sheathing above the ventilation channels -- unless, of course, you are installing a type of metal roofing that requires this type of sheathing.

4. 
   jordangarrow | Oct 15, 2015 06:28pm | #4

   Martin,

   I was under the assumption that a cold roof required a layer of sheathing under the metal roof. That's what I'm trying to avoid. Thanks for the information!