I’m almost finished with my new metal building. It’s basically a wood post and beam, metal sheathed garage…no insulation, no interior finish, no plywood roof decking. The metal is exposed on both sides. The top two feet of the side walls are screened for light and ventilation. (In fact, one end wall is still open.) I know about the principles of condensation, but did not expect it to occur because the temperature above and below the metal roof is equal and there’s plenty of air flow. Do you think interior roof insulation with a vent space above would solve the problem or merely catch the drips?
Dave
Discussion Forum
Discussion Forum
Up Next
Video Shorts
Featured Story
Key proposals for the next edition of the International Residential Code tackle room sizes, stair specs, emergency egress, and deck guards, among other requirements.
Featured Video
Highlights
Fine Homebuilding Magazine
Fine Home Building
Follow
-
Fine Homebuilding
Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.
Start Free Trial Now -
GBA Prime
Get instant access to the latest developments in green building, research, and reports from the field.
Start Free Trial Now
- Home Group
- Antique Trader
- Arts & Crafts Homes
- Bank Note Reporter
- Cabin Life
- Cuisine at Home
- Fine Gardening
- Fine Woodworking
- Green Building Advisor
- Garden Gate
- Horticulture
- Keep Craft Alive
- Log Home Living
- Military Trader/Vehicles
- Numismatic News
- Numismaster
- Old Cars Weekly
- Old House Journal
- Period Homes
- Popular Woodworking
- Script
- ShopNotes
- Sports Collectors Digest
- Threads
- Timber Home Living
- Traditional Building
- Woodsmith
- World Coin News
- Writer's Digest
Replies
Although the air is presumably quite close in temperature above and below, the metal is often not the same temperature as the surrounding air as it heats and cools more slowly.
Airflow only does so much to eliminate condensation, that's why the standard detailing for metal roofs has moved away from skip sheathing to sheet underlayments in direct contact with the underside, which appears to be more effective - sort of like the insulated roof of a car.
Before you go too far trying to remedy the problem you might want to watch it for a while. We built a metal shop that had heavy enough condensation that it rained inside for the first month, but has never had any problem since.
I've dealt with this a couple of times for one customer--remove the metal roofing (installed over purlins with no felt), remove the purlins, install a CDX deck, install Ice and Water Shield over the entire deck, and reinstall the metal roofing. It solves the dripping problem.
Google 'night sky radiation'... interesting reading.