100 year old barn - heated- advice needed

Guest User
9/30/2015
I have a 100 year old barn that over the years has been added onto and heated. The large attic space is unheated and unvented (except for the few gaps here and there- it is like a large closet in my mind- albeit a very hot one in the summer. There is insulation (30 years old) in the ceilings. The old roof has to come off (65 year old T-Lok shingles) over wood shakes. After researching I am more confused than ever. I hope to keep the noise level down, and for that I understand that attaching to the new plywood decking is best. With the lack of good insulation and venting I understand that using purlins (or battens?? ) and leaving an above deck air flow. I also hear that if roof is off deck, it tends to condensate alot. But if it is against the decking it probably would too with the bad venting. My initial thought was to ice & water shield the whole roof and put on the roof. Also a reflective barrier - but where does should that go? Also should the ribs be sealed? If it is put on purlins should you use a underlayment on top of the purlins also? HELP! Any help is appreciated. bob
Info @windowsonwashington.net
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9/30/2015
Bob, Will you be using it as a conditioned space?
Guest User
10/1/2015
Yes - the first floor is conditioned. Insulation in the ceiling -30 years old 3" fiberglass batts. Not kept at 75* by any means, but is heated to 60's in day and 40's at night.
Info @windowsonwashington.net
An informed customer is our best customer.
10/1/2015
If the roof isn't vented, vent it and insulate the attic floor. Google about air sealing and insulation. It is critical to keep the conditioned and moisture laden air in the living space. If you keep the attic free from conditioned air, the natural convection of the attic (when vented) will remove any residual moisture and keep it from sweating in the future.
Guest User
10/1/2015
Thank you for the ideas. I realize how the usual venting works but in this case the attic has been sealed for 100 years. The last asphalt roof lasted 65 years without curling or warping due to high heat of an un-vented attic, so I am hesitant to open it up to full circulation. Plus there are a lot of accumulations in the attic so it would be impossible to insulate the floor very well. I think of it as a large closet- although it does get hot in the summer and cold in the winter, it is by no means air tight- it must be venting enough to keep moisture out. I am concerned on how best to put the roof on while retaining the attic storage. I have talked to more folks today (steel roof manufacturers) that have even more ideas- but they don't follow any common thread. People have been building buildings for hundreds of years, it would seem like there should be a "standard" way to do this, or at least a similar set of rules.
Info @windowsonwashington.net
An informed customer is our best customer.
10/1/2015
High heat isn't the issue with shingles or roofing in general. Its moisture and condensation. You have been unintentionally conditioning that attic space. By doing so, the sheathing and framing was at a temperature that kept condensation at bay. If you are doing a solid deck (plywood), you shouldn't be any more likely to form condensation at this point if you left well enough along and insulated the same way. That being said, that isn't the most efficient way to go. A picture will help me here as well, but, better to move the insulation and air barrier to the attic floor and just vent the roof. That will keep the moisture out of the attic and insulating and air sealing will keep the conditioned air (i.e. the stuff with the moisture in it during the winter) in the space below and out of the attic.

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