With tribuilt granulated self adhering underlayment on top of the plywood.
Unvented roof using sips.
Do use sealant on wood to wood wood to eps and eps to eps connections.
A sure bet would be to use 6 of eps above the roof deck or a 6 sip for r25 then finish it out with 6 of better quality high density spray fiberglass sprayed onto the underside of the roof deck to acheive an even better clear assembly r value than 14 of blown fiberglass since the eps is now thermally breaking the i joists.
If you don t want to use sips or nailbase there are four basic approaches.
Do use sip tape or equivalent vapor retarder on roof panel joints.
This will create an air space over your panels which will allow them dry out if moisture escapes.
Cost aside the most straightforward route is spraying closed cell polyurethane foam on to the underside of the roof deck.
Four options for building an unvented roof assembly.
The roof is currently built as follows.
Unvented roof here again the choice of what insulation to use and whether to install it over or under the roof deck depends on the condition of the present roof the depth of rafters the r value you must attain and cost.
B use a wrb that is vapor permeable on the top of the roof sips underneath the standing seam metal roof so that if somehow any moisture does get down to the roof sips it has the ability to permeate outward.
Beams on 5 centers.
This is a pretty common procedure when using roof sips.
A use a material that is not vapor permeable over the t g ceiling boards and under the roof sips to prevent moisture migration from inside the building to the underside of the roof sips.
The only way i know of venting a sip roof is to build a cold roof over the existing sip roof which brings up another question as to the benifits if any of a cold roof with a sip roof.
Next i ll be screwing down 5 1 2 raycore sips panels over heated space and framing boxes over the eaves covering everything with 5 8 cdx.
1 1 2 t g decking.
Why use closed cell spray polyurethane foam ccspf.
Do install proper flashing and sealants around all rough openings and penetrations as required.
The design approach is the same for all climate zones.
Sip s are almost air tight and won t leak air so you don t need ventilation.
We feel a cold roof is not necessary if your roof sips are sealed properly.
The ventilation space can be eliminated and the construction greatly simplified by using an unvented roof assembly.
Closed cell spray polyurethane foam can be used to create an unvented roof assembly that works in all climate zones.
Extreme s pre insulated sips offer an option for a high performance roof framing solution that is 15 times tighter than conventional construction practices making it easier to control indoor air environment.
Cold roof a cold roof is achieved by adding strapping and another layer of sheathing over the sips.
Need to make a final decision on which underlayment to use under a metal roof on an unvented roof system.
Unvented roof assemblies should be insulated either with air impermeable insulation rigid foam or spray polyurethane foam or with a combination of foam and air permeable insulation.
