Spray foam against plywood roof decking questions
I currently have the following roofing system and am located in Northern WV in climate zone 5. Fabral standing seams metal roofing, tar paper and then plywood on 2' center bonus room trusses. I am getting quotes on insulating the underside of the roof decking with spray foam. The HVAC units and ductwork are located in the attic space beside the bonus room. Here are my questions and concerns.
1) I have a vented soffit and vented ridge vent at the moment and should I put up something to keep the air flow before spraying the foam or create a unvented attic space instead with the foam?
2) Should I go with open or closed cell against the roof decking due to vapor barriers and moisture buildup and concerns.
3) What R value/Inches of foam should be on the attic. I have had to people out here to give me a quote and they both seem to want to skimp on the foam and only do around 20 R value but both are using products from LaPolla.
I can't go back and put insulation under the standing seam so this all needs to be done correctly from the inside and any suggestions would be great. Please let me know if there is any other information I should provide or take a look at. I have read many posts but wanted to make sure since there is a lot of mis-information out there.
Posted Mon, 06/02/2014 - 05:13
Edited Mon, 06/02/2014 - 06:14
Other Questions in Energy efficiency and durability