Standing Seam and Insulation

Jeff Frantz
3/20/2012
Hi! I am planning to have a metal roof installed in the next few months and wanted to run some of the details past the experts to see if you had any comments. The house is a 1.5 story cape code style home. It is a difficult house to ventilate with some areas being cathedral ceiling and some areas having an attic space. The main part of the house is an exposed beam with T&G wood ceiling. This area currently has 1" of expanded foam with 1/2" plywood covering it and asphalt shingles. No venting. The rest of the house either has fiberglass between the rafters and a cathedral ceiling or an attic with an insulated floor (only area that is vented). My main area of concern is the area with the 1" of expanded foam. My plan is to have the 1/2" plywood decking and 1" foam removed and then ice and water shield the T&G wood (idea I picked up from this site). Then put down 1 1/2" foam to build the roof back up to the height of the existing roof and then install an additional 3" of polyiso to the entire roof. The perimeter of the roof will have double stacked 2x4's in areas where there is 3" of foam and (3) 2x4's where there will be 4.5" of foam. The roofing company with the best references and a good price said they would install the standing seam metal (Berridge 26 gauge) roof directly over the foam. They would use bearing plates to distribute the surface area under all clips to secure the panels. I would like to vent this area, but I am at the top of my budget already with the insulation and metal. What are your thoughts or concerns? Also, there are 3 skylights that will be replaced. I am having trouble finding a manufacturer that makes skylights with a wood interior. Velux doesn't make a vented skylight with anything but a white interior. They seem to be the most popular brand out there. Do you know of any manufacturers that make skylights with an unfinished wood interior? Thanks for any and all help. Jeff
Todd Miller
Isaiah Industries, Inc.
3/21/2012
Thanks Jeff. I am going to open this up for public comment. I have never been a fan of installs over foam with no decking but let's see what others think. Sorry, too, I cannot help on the skylight. Well, maybe I can. Have you checked into Pella?
Eric Novotny
An informed customer is the Best Customer!
3/21/2012
Where is the home located? Love the idea of the ice and water (I think that was me) but would love to see a bit more foam and some plywood decking as Todd mentioned. This is a one time shot here and I would seriously encourage you to just expand the budget a tiny bit more for additional foam and some above deck venting. Post back where the home is located and I will be happy to add more feedback.
Jeff Frantz
3/26/2012
The home is located just west of Chicago. I am concerned about the weight of the roof also. Installing the metal over the insulation will cut down on the additional weight of the plywood decking. What would the concerns be going directly over the foam? I looked in to Pella for the skylights at if refers you to Velux. Anderson also no longer carries skylight. I may just have to go with all fixed skylights. Thanks for your help! Jeff
Todd Miller
Isaiah Industries, Inc.
3/27/2012
My concern over foam is that, even though the foam is rigid, when the roof is walked on, it may compress into the foam and, when that happens, the integrity of then interlocks between the panels can be jeopardized. This is a greater risk with some metal roofs than with others.
Eric Novotny
An informed customer is the Best Customer!
3/27/2012
Deflection and walk-ability are the two biggest issue with metal directly over foam as Todd mentioned. Plywood will not add that much weight and when you figure on the lighter than asphalt option of metal, you should not anywhere approach the weight loading maximums of that structure.
Jeff Frantz
4/3/2012
Thanks guys. The roof is a 9:12 so I am not sure the walk-ability of that with a metal roof. I will check the price if we include plywood and maybe even get a cost for the vented nailbase from Atlas or Hunter. I want to do everything I can to do it right, but this project is nearing the top of the budget.
V Cijunelis
11/24/2013
Jeff, did you ever do this roof? I am looking at a SS roof from berridge aswell, and haven't had any luck with any contractors that want to even attempt screwing through 3" of foam without charging a lot more money. I am in chicago area as well, which is why i ask. Who did you use? Proper venting or "hot roof" while controlling dew is the concern. I will have all catherdral with 14" TJI joists, 24" o/c, with the metal roof i've been told to just spray 11" ocSpF under the sheathing and be done, and others say that won't work because of the metal roof. I am considering: 1) spraying theunderside as mentioned with demilec agribalance to 11" and drywalling over the top 2) ripping 2" rigid board insulation and wedging it between the TJI rafters, leaving the top 1.5" open for a vent, the blowing closedcell SPF under that 2" thick, the filling the rest with unfaced fiber batts to reach desired R, then drywall over that 3) R38 batts, with 1" poliyiso rigid on the inside of the ceiling and gyspum drywall over that, but the fiberglass batts wont perform as well.
Eric Novotny
An informed customer is the Best Customer!
11/24/2013
Don't do option 3 in any capacity. It will not perform and possibly create issues. Option #2 is my favorite in this case and you don't need a real heavy application of CC SPF in this case as you just need it for air seal. The rigid board will control moisture and the vented space will dry whatever does go through. One revision, I would ditch the batts and go with something like spider insulation in lieu of the batts.

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