There seems to be a debate over fastening roofing material directly to a SIP roof panel or providing an air space for any heat/moisture to vent. My question is simply this: On a single story house why can't you get Sip panels for the walls, put up your interior partitions then lay SIP panels horizontally across the walls at the ceiling height? Once that is done make a conventional roof from there on up with trusses or stick built and totally ventilate it. This would also require less SIP material overall.

Using SIPs for the walls and ceilings work well. However, this method does not seal and insulate the attic. If HVAC ducts are in the attic, then it becomes more important that the attic be sealed and insulated.

Sips at ceiling level is a common residential builiding configuration when building with sips. As Alton suggestes this configuration does have some drawbacks.

Thanks for the feedback. I live in upstate NY so we see all seasons here. I'm thinking about going with geothermal heating/cooling on a single floor house. When SIPS are used horizontally as a ceiling rather than a roof are they reinforced where they meet the exterior walls to support the added weight of a conventional roof?

As far as support goes, I would suggest the SIP ceiling resting on the exterior walls with added support within the house. Support beams can be placed within the walls to support the roof weight. Then, conventional roof trusses on top of that. Of course, I would have a structural engineer familiar with SIP’s design the support system. It seems to me that the basic idea is to build a tight, well-insulated envelope. If you use SIP’s as a roof or a ceiling, I really don’t see any difference. A plus is, there’s much less area to heat than a room with a cathedral ceiling. Just build a standard, ventilated roof over your SIP ceiling. Drawbacks? Well, a couple. First, if you use SIP’s for the ceiling, then you will have the added expense to build the trusses and roof support. If you want a ceiling, it may be cheaper to put a foot of blown in cellulous. If you use the SIP’s for the roof, you can have a have a cathedral ceiling, and the rooms feel much bigger.

Steve
GrandCountySIPs.com

Bill E, Be aware that the type of skin on a SIP can vary the detail for attachment. For instance, a ceiling or roof SIP with OSB skins may attach differently to a wall than a SIP with metal skins. When in doubt, talk to the supplier and read the installation manual.

In the suburbs around New Orleans and Baton Rouge they "Flat Box" OSB SIPs for housing all the time. They have a "French Provincial" housing style there with very tall hip roofs (12 in 12, 14 in 12) and it's easier and cheaper to hand frame these long spanning, complex roofs with sticks instead of SIPS. It's a 'wood culture' area as regards construction and they are comfortable onsite rafter framing these roofs over the flat SIPs. There is no single answer for every project. Each design and region/location will determine the best use of materials.