Sid Hogan
hard way
6/13/2014
Need some guidance on using foam board on top of roof deck beneath metal panels. This is an unheated, uninsulated barn barn with pine board roof decking. I would like to cut some of the heat coming through the dark color roof in summer. In winter I will occasionally run a heater on the second floor while working inside. My roof pitch is 7/12. I'm planning ribbed 29 guage panels with external fasteners. I'm thinking the roof is going to leak a little eventually in big wind and snow conditions and I would like to shed water that gets beneath the panels. Should I use WIP over the foam board or beneath the foam? Any other options? I could use a foam board product recommendation as well. There are no valleys or dormers or cupula. Planning 1 x 6 nailers over the foam to screw down the panels. I'm not sure this 3/4 inch air space counts as roof ventilation. I sincerely appreciate your thoughts on this.
Info @windowsonwashington.net
An informed customer is our best customer.
6/14/2014
Go with the above deck ventilation as you are leaning towards. Putting some foam across the roof deck should help with the surface temps in the winter and keep condensation issues to a minimum. Use the underlayment over the foam board. I would also look into sealing the pine boards by applying a peal and stick membrane. This will keep any of the air movement and condensation on the underside of the panels to a minimum.
Sid Hogan
hard way
6/16/2014
Thanks For the foam board, any recommendations or types to avoid?
Info @windowsonwashington.net
An informed customer is our best customer.
6/16/2014
No types to avoid. XPS and PolyIso are the most common.
Guest User
7/25/2014
I am sitting here watching a Decra steel roof being installed but they did not install any foam insulation under the steel like my previous aluminum roof? We are concerned about our energy costs rising - they are very low in this home. We also want to know if it should have some. thanks!
Todd Miller
Classic Products, Inc.
7/25/2014
Deena, while the foam inserts did offer some energy efficiency, these products do have some efficiency without them. Is this a batten-mounted Decra product?
Guest User
7/25/2014
Yes they laid batten and a plastic sheet under that. Not sure what that us. Sorry. I'm no expert. Thanks!
Todd Miller
Classic Products, Inc.
7/25/2014
The battened systems are pretty energy efficient. My guess is that your overall efficiency may decline a little but probably not a huge amount. Anytime you change any components of the roof system, you are at risk of this. The system you had was one of the more energy efficient ones available.
Guest User
7/25/2014
Ug my roofer said this one would be more efficient. ??
Todd Miller
Classic Products, Inc.
7/25/2014
Do you know by chance if they put down vertical battens first followed by horizontal battens, or only the horizontal battens?
Guest User
7/25/2014
I'll go out and look. They are literally installing right now. Horizontal only.
Todd Miller
Classic Products, Inc.
7/25/2014
That is the normal method. The battens create a nice thermal break between the metal and the roof deck, which really is very similar to foam in terms of efficiency. There is a method of vertical battens first which allows for good passive ventilation airflow up the roof. It will be interested to see how the roof performs. Please let me know once it's up. My email is [email protected] My hunch is that it won't be hugely different from your previous roof. I don't expect it to be quite as good but I do not expect it to be hugely different. Good luck.
Info @windowsonwashington.net
An informed customer is our best customer.
7/26/2014
Deena, What panel did you select? The thermal brake should be in tack and there will be some convective air movement.
Guest User
7/26/2014
So I'lm attaching an image of the packaging so you'll know what we chose. I'll watch our bills and see if there's a big difference. We are in the peak of summer in Texas so it should be interesting. Thank you!
Info @windowsonwashington.net
An informed customer is our best customer.
7/27/2014
Going with the shake they do have an Energy Star color but that does not appear to be in that color range. There is still a decent bit of air movement under that panel so you should be good.
Guest User
8/12/2014
I am considering a metal roof. Their practice is to install a synthetic material (plastic type feel to it) which is water proof on the decking before the ag panel is installed. Is this enough noise barrier product or should it be an ice/shield or foam product which is thicker? When the ag panels are joined side to side shouldn't there be a lap sealant put underneath to keep moisture out? If they don't use a sealant to join couldn't this be a problem for leakage?
Todd Miller
Classic Products, Inc.
8/12/2014
Some panels are designed for sealant in the side lap and some are not. You do not want to add sealant to a panel not designed for it. The synthetic underlayment you described is not a noise barrier. Normally any additional sound from a metal roof is absorbed by attic space and insulation.

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