TOPIC: I Have An Existing Metal Roof and Have A Question
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Hello. We have recently had a small two story 24' x 30' cabin built with a standing seam metal roof. The contractor advised installing the metal bare over wood purlins, without underlayment or plastic bubble type barriors, in anticipation of using closed cell spray foam as vapor barrior/insulation. We have since decided against using the spray foam and would like to know how to go about insulating? The unvented roof will be directly over a conditioned small loft bedroom. Any help will be greatly appreciated!
Is there an attic space that can be insulated or vented? Additionally, I strong encourage the inclusion of a very good vapor barrier on the bottom side of the insulation. In a small space like this, you are at great risk of moisture generated inside the structure reaching the bottom side of the metal and condensing, especially during spring and fall seasons when the evenings are cool but ambient humidity levels are high.
Hopefully they did use the bubble underlayment/radiant barrier here and were careful about their seam details.
Can you post up a picture of the interior?
Here are a few pics. Bubble underlayment was not used...can this be added after the fact?
Hmmm...are you going to be dry walling the walls and ceilings?
+1 to Todd's response. Unless you are going to spray foam this, you are going to be best suited to drywall this ceiling.
It looks like you might have soffit vents for intake at the bottom? Is there a ridge vent for exhaust? My recommendation would be just normal construction after that ... drywall with a good layer of polyethylene behind that as a complete vapor barrier and then insulation on top of that. Or else go back to the previous spray foam idea you'd ruled out I believe you said?
The area will be finished completely with drywall. My concern was in condensation forming behind the drywall, even with a polyethylene barrier to the interior side as it is such a close space. Is this not the case? Would it be beneficial to use a rigid foam panel insulation against the metal surface with a mineral wool batt insulation and a polyethylene vapor barrier against the drywall? There is a ridge vent of sorts, however the soffit vents are minimal. I could increase the soffit ventilation or close the ridge vent and treat as unvented. Can you advise which would be a better scenario and if venting, how much of a gap would be needed for air flow as the horizontal purlins disrupt the flow.
My roof was constructed like these photos 12 years ago, then insulated with fiberglass batts, then drywall. The drywall is attached directly under the ridge and rafters without an extra air space. No other vapor barrier used, or underlayment between the metal and purlins. The ridge is vented with a mesh, and screens are installed along the underside of the soffits for airflow. We have a 10/12 pitch. However, the intense seasonal winds have driven rain up under ridge and through the mesh, and caused water damage on cathedral ceiling. I also suspect the winds pushing through the soffit screens have shifted the insulation where it meets the wall so we are losing indoor climate control. It has been suggested we completely seal the ridge vent and soffits to solve this problem. Would that fix our issues, or cause more? We live in the midwest with hot humid summers and cold winters. Looking for a solution that doesn't entail removing the roof.
Michelle, I am sorry ... somehow we missed a response to you back in August. Are you still seeking responses? To the author on 10/2, without a vapor barrier inside the home, I'd be concerned about just closing off the ventilation. When you do that, all the moisture that is generated inside the home (by cooking, showering, house plants, on and on) will be held inside the home and when it finds a cool surface on the inside of the home's outer skin, it will condense.
Need solution with right way to insulate a non insulated pole barn coverted into a home. Do not want to use spray foam.
I strongly suggest some sort of complete vapor barrier directly behind the drywall. Is there any way to ventilate the space above that?
I have an old cabin on my property that I want to improve the insulation. There is currently cellulose on the floor of the attic. It has metal roof on batten boards but no other insulation. There is no evidence of water damage. Should I make the floor insulation better, spray foam the ceiling, or other suggestion
Thanks Trent. What is your intended use of the cabin? Yes, spray foam is not a bad idea but if you do not intend to heat this space or use it as living space, it may be unnecessary. Also, if the space is already heated, you may start to have condensation issues if you tighten up the walls, windows, and doors. In that case, the closed cell spray foam would be helpful.
We are going to live in it
Condensation occurs in the building envelope when warm moist air originating inside the living space is trying to drive its way out and it reaches a cool surface. As the air "shrinks" moisture is forced out of it and condensation occurs. Condensation is avoided through vapor barriers, insulation, and ventilation. The closed cell foam creates a vapor barrier and is also a very good insulator. I think that would be a good idea.
Thank you for your help, would you recommend putting foam on the ceiling or floor of attic?
Do you recommend spraying insulation to ceiling or floor of attic?
One key to spray foam is doing it well. Any breaks or voids where foam is not will become problems for moisture transfer and condensation. You could spray foam the attic floor or the back side of the roof. Or both. If done well, any of these options will be very helpful.
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