Scott Robinson
1/29/2013
I just purchased a house inear the beach on the Washington Coast. It is a contemporary, cabin style building (built 1976) -(28' x 28' footprint) with a cathedral style ceiling (double 2x10 built up beams under 2x6 car decking). Currently it has three layers of composition roofing over what appears to be an inch of foam board, which lays on the 1.5" car decking. It's old and in poor condition, but is not leaking, but has leaked (and stained the interior ceiling) in the past at the propane chimney perforation and possibly in other locations possibly due to condensation. The roof is an offset rake and pitch, with a 28' rake on the longer side (10/12) and 16' on the opposite rake (6/12). I got a bid from a licensed, bonded contractor in our area who says he will perform the following: 'Remove existing multiple layers of composition roofing Install Deck Defense Synthetic moisture barrier underlayment Install drip edge metal and gable end cap metal Install 1" insulation board Install 1/2" CDX plywood sheeting Install 12" Snap Loc Standing Seam Metal roof panels Install new pipe flashings Install new ridge cap with closure strip 10 yr Labor guarantee 130mph wind uplift protection ================================= So now, my questions: Is the contractor's proposed installation adequate to prevent leaks and/or condensation problems? Also, I have read on some building forums that TWO layers of iso board, at 1.5" each, for a total of 3" of insulation is recommended. It has and inch of foam board now, (contractor says it will be too damaged to save after removing the multiple layers of compostion roof.) Is there anything being left out of this installation and finally, will the R-value of that single layer be enough? This is a vacation home, used primarily in the summer (temps rarely exceed 75 degrees nor go below freezing). Thanks, Scotty
Todd Miller
Isaiah Industries, Inc.
2/1/2013
I am a little concerned that this could cause condensation issues. Because standing seam roofing has a lot of direct contact with the substrate beneath it, cold is transferred downward. This could drop the temperature enoygh that condensation occurs where it dod not occur before (and honestly I wonder if it hasn't occurred some in the past). My suggestion would be to add some more insulation...that will help stop the transfer of cold and reduce the possibility of condensation. All Best.
Michael Stallcup
2/2/2013
Hello. I have a lake house and am exsperiencing condensation trouble. It is 1,300 sq ft. Almost all is under an attic, accept for the living room. It was an add on. No attic. The metal roof was applied directly to pre-existing shingle roof. The condensation literally runs at times on to the deck, avoiding the gutters. I thought not much of it, until i recently noticed the wall joints on that side of the room starting to seperate around the fire place and bay door. My ignorance asks, "Is this condensation the cause of the interior damage?". No moisture inside. I did not install the roof. I need to stop any more damage. Any info will be carefully considered! Thanks
Todd Miller
Isaiah Industries, Inc.
2/6/2013
Michael, so you're talking about dew forming on the outside of the roof?
Guest User
6/4/2013
Hi, I need some help here. We are building a log home with a 10/12 pitch, metal room, with a cathedral ceiling. We are looking for help to figure out how to Insulate this metal roof. We have 22" space between the metal roof and finish ceiling. The house is in Canada and we do get cold weather here. We are thinking of using " true vents and the baton R-20 X 3 to make R-60 and then use one layer of "Level wall " insulation that has the tin foil reflector tape on it at the finish side. We are concerned about condensation. Does anyone have a solution ?
Eric Novotny
An informed customer is the Best Customer!
6/5/2013
Michael, If the condensation is to the exterior, there is nothing to be done about that. In some cases, it is a good indication of an insulation systems performance because it is keeping the exterior surface colder. We field this concern from customers who see condensation that was not there previously.
Guest User
10/22/2013
Good afternoon. Chicago, zone 5, metal roof, cathedral ceiling, TJI14" rafters, new construction. I have done lots of research - it seems that financially, there are a few options available to me: 1) for an air gap, put in R38 HD batt that leaves 3" gap at the sheathing and call it done. 2) put in R38 HD batt leaving 3" vent at sheathing, and put 1/2" polyiso on interior with drywall over that. 3) spray foam layer against sheathing, fill the rest with R38 batt for no vent install For 1 & 2, I am concerned about the 24" OC spacing of the TJIs that have 3/8" web thickness. There isn't much compression on the sides of the batt - will I get a good seal? For 3, how much spray foam is needed for Z5 and is closed or open better? Open seems to collect moisture eventually. Also, isn't there a dew point issue with this type of installation that eventually will cause problems? The TJI wood will have less R value than the spray so won't dew happen deeper in the cavity through the TJI web?
Eric Novotny
An informed customer is the Best Customer!
10/23/2013
You are going to need minimum R38 for code these days. While I like SPF, it is expensive and does not address the thermal bridging aspect of the framing. The I-joists have less bridging potential than traditional lumber but I would still love to see some rigid foam to the exterior in this case if you are going with a sealed system. If not sealed, vent the roof system and do a hybrid install with a vented space, created by full span rigid foam, spray to the back of that for proper air seal, and fill the rest of spider or similar spray fiberglass to keep the cost down.
Eric Novotny
An informed customer is the Best Customer!
10/23/2013
http://www.finehomebuilding.com/how-to/articles/a-crash-course-in-roof-venting.aspx Google - A crash course in roof venting. Great read.
Guest User
10/27/2013
I planning on building a house using a pole barn style building with metal trusses on 10's centers and 2x8 purling with a metal roof. I want to have an exposed interior cathedral ceiling, but I also want good insulation. How should I approach this problem?
Eric Novotny
An informed customer is the Best Customer!
10/27/2013
SIPs deck or rigid foam on the exterior.

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