Denray Posted October 24, 2011 Report Share Posted October 24, 2011 I was looking at a roof this morning with my wife, the claims adjuster, where there was ridge venting only. The comp shingles were on top of OSB that had 6 inches of Styrofoam type insulation sandwiched between another layer of OSB on the bottom. Across the field you could see where all the rafters were as if zinc had been dripping down from above. Many rafter bays were a bit sunken and the bottom edge of the top sheathing was moist and rotting. The interior drywall of the cathedral ceilings showed no damage. I wonder what is going on. No photos. Quote Link to comment Share on other sites More sharing options...
Marc Posted October 24, 2011 Report Share Posted October 24, 2011 Ridge venting of rafter bays where styrofoam is installed between the top of the bays and the exterior? Do I have that right? Marc Quote Link to comment Share on other sites More sharing options...
Richard Moore Posted October 24, 2011 Report Share Posted October 24, 2011 You might want to take a look at the the Structural Insulated Panel Association website at http://www.sips.org/ . Everything there seems to suggest that the interior of SIPs roofs should be conditioned and should not have the venting typically found in normal attics. As least, that's my read. See the ridge detail diagrams at http://www.sips.org/technical-informati ... on-details and the "Juneau issue" at http://www.sips.org/technical-informati ... roof-issue. The following is also from the FAQs section... What about roofing? Does a building with a structural insulated panel roof need to be ventilated?A: The area inside a SIP building envelope is considered conditioned space and will be ventilated by the building?s HVAC system. There is no need to provide a vented attic beneath a SIP roof, and doing so would compromise the conditioned space of the building. Most roofing manufacturers specify how to attach their product to SIPs. Please contact the roofing manufacturer for application instructions. Does a building with a structural insulated panel roof need to be ventilated? A: The area inside a SIP building envelope is considered conditioned space and will be ventilated by the building?s HVAC system. There is no need to provide a vented attic beneath a SIP roof, and doing so would compromise the conditioned space of the building. Research conducted by Building Science Corporation on test homes in hot climates demonstrates that including the attic in the conditioned space allowed for more energy-efficient space conditioning and less probability of moisture related issues. Some building science experts, such as Building Science Corporation Principal Joe Lstiburek, have advocated venting the roof by providing an air space between the SIP roof panels and the roofing material (known as a ?cold roof?). This practice is not a requirement for SIP buildings, but an extra measure to improve the durability and moisture resistance of the building. I'm certainly no expert on SIPs homes, and you should probably defer to a SIPs expert, but it does seem that the ridge venting might be creating unwanted air-flow and causing the problems you observed. Quote Link to comment Share on other sites More sharing options...
kurt Posted October 24, 2011 Report Share Posted October 24, 2011 That's my read too. Conditioned space, no vents, just like closed cell. Which basically, it is. Quote Link to comment Share on other sites More sharing options...
smarcus Posted October 25, 2011 Report Share Posted October 25, 2011 http://www.buildingscience.com/document ... l-climates Building science has another article too that I didn't bother to find but that might be helpful too. Quote Link to comment Share on other sites More sharing options...
Denray Posted October 25, 2011 Author Report Share Posted October 25, 2011 Hark! You all nailed it. Here's some photos. Click to Enlarge 51.45 KB Click to Enlarge 69.17 KB Quote Link to comment Share on other sites More sharing options...
Denray Posted October 25, 2011 Author Report Share Posted October 25, 2011 I bet the rain is blowing in, dripping down the squar cut faces and getting sucked into the OSB-Styro, and with no vent it just sits in there rotting away. Thanks everyone. Quote Link to comment Share on other sites More sharing options...
Tom Raymond Posted October 25, 2011 Report Share Posted October 25, 2011 No one else mentioned it so I will, I think you have a case of ridge rot and it's condensation running down those panel joints and not rain water. The standard ridge vent was probably an attempt to fix it. Go to buildingscience.com and search out 'ridge rot'. Dr. Joe has a decent fix for it on there somewhere, but it ain't gonna be cheap. Quote Link to comment Share on other sites More sharing options...
Jim Baird Posted October 25, 2011 Report Share Posted October 25, 2011 With no "attic space" to vent the vents at top are superfluous, no? BTW, if you were there in company of "the adjuster", what kind of claim was made?, or was it incidental? Quote Link to comment Share on other sites More sharing options...
Chad Fabry Posted October 25, 2011 Report Share Posted October 25, 2011 What Raymond said. It's a problematic issue that is hard to fix. Quote Link to comment Share on other sites More sharing options...
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