Find a Professional
Sign Up Log In Add New Topic

TOPIC: I Have An Existing Metal Roof and Have A Question

Condensation dripping through ceiling

Return to I Have An Existing Metal Roof and Have A Question

Return to Forum

I have a small ( 16 feet by 24 feet) barn type metal building that I finished on the inside to live in with plans to build other rooms on to it in the future. I am living in it at this time. 2/3 of the building has a loft. This part has Styrofoam insulation attached to the rafters. The other 1/3 has a ceiling that follows the barn style lines. The roof is built on 2 x 6's. The roof is covered with a lightweight metal (not steel) that I believe to be called galvalume. The ceiling in the part that does not have a loft is covered in 1 x 10 boards with fiberglass batting between the boards and the metal. There is nothing else up there. My problem is that since I have started using space heaters water is starting to drip through the insulation and boards when the weather is cold and condensation or frost has formed outside. The roof does not leak when it rains. What is the best solution for this other than tearing the metal off and replacing it with a different type of roof? There is no ridge vent or any other type of attic ventilation. Since there is only six inches between the metal and the wood and it is filled with batting insulation, would a ridge vent help? I had a roofer to come out and look at it and his recommendation was to put what amounts to a new three part roof over the existing one. This would cost quite a bit of money. Is there any other option? Would ridge vents help? Would attaching foam sheets to the underside of the metal help?
ROSEMARY CAGLE

12/12/2014
Nothing is wrong with the roof. The issue with the condensation that is the result of the warm air migrating up around the unsealed insulation and kitting the cold underside of the metal roof. You need to address that air leakage around the insulation by any numbers of methods (i.e. spray foam, new insulation, rigid foam, etc.). If you decide to vent the roof, you will have to take down the insulation regardless. Eric Novotny
Eric Novotny
An informed customer is the Best Customer!

12/12/2014
Are you saying that if the roof is ventilated I shouldn't have the batting insulation there? Also I read somewhere that rigid Styrofoam could be installed on the underside of the roof between the rafters. The writer suggested keeping it in place with spray foam around the edges of the Styrofoam. Do you think that this is a adequate solution? Would there be a need for any type of roof ventilation if I did this? Thank you so much for your reply.
ROSEMARY CAGLE

12/12/2014
No. The roof is, in all likelihood, not vented, however, the insulation layer across the roof is not complete or air tight. Installing rigid foam in the rafters bays will work. Any insulation you install needs to be sealed so that inside air cannot reach the underside of the roof and for the resultant condensation. Eric Novotny
Eric Novotny
An informed customer is the Best Customer!

12/14/2014
Thank you.
ROSEMARY CAGLE

12/14/2014
I have a Steel framed house with a steel purlin roof system on 5' spacings. I built house with10'of insulation between purlins, and then 2'' over the top of purlins in opposite direction. Then have standing seam metal over this. house is 12 years old and I notice a small drip from my ceiling in one area of the house with cathedral ceilings. I am concerned that this has been going on for years without notice. How to determine a problem, as house is going to be for sale shorthly. Thanks Steve
Steven Swearingin

1/1/2015
Steve, What are the vapor control layers like? Is there drywall? Any vapor barrier? Eric Novotny
Eric Novotny
An informed customer is the Best Customer!

1/3/2015

If you would like to reply to this thread, please log in. If you do not have an Ask the Experts forum user account, create one here.