Stopping Condensation Metal Roof

I’m closing in a covered back porch to make a future office. I was hoping the insulation would stop the condensation, but as it got pretty cold last night, and warmed up this morning, the bottom of the metal panels began pouring water through the insulation.

To stop the condensation, I’m thinking I can

(1) Take up the metal panels, put plywood down over the purlins, then tar paper over the plywood, then re-install the metal panels, or

(2) Take up the metal panels, install 1/2 inch foam board insulation panels on the purlins, then re-install the metal panels.

I’ve researched a little about spray foam, but not sure how effective it would be.

Any suggestions would be greatly appreciated

Once you insulate and condition the inside air it will stop. You will be changing the dew point.
Is this location going to be in conditioned air?
Vinyl backed insulation is your best bet.
I wouldn’t let the insulation come in contact with the metal. It need to be ventilated.

Or you could buy this…
I’ve seen people use the Thermo-ply, but I’m not sure if it will work in your case.

I like plan 1. :wink:

He does not understand (thunder storms) When cold temps meets warm temps ya have rain!!!;-):shock:

The spray foam is a good idea. I’ve seen it used on many commercial metal buildings.

Seeing a lot of spray foam around here.

Check this out…
Insulating Metal Buildings with Spray Foam

Roy, my brother, the inside is conditioned and insulated (see pictures). The insulation is not contacting the the metal. There is about a 2 or 3 inch void over the insulation for air space. The metal is getting cold, then heating up from the sun in the morning, causing it to sweat. The insulation is catching the dew. I need to stop it from condensating on the underside.

I’m sure I understand thunderstorms, Red Hat, I’m just not sure how to stop them from occuring INSIDE my house, lol!

I’d do the foam…Yep!
What is the size of the metal roof area.

Your condensation is created before the sun has a chance to hit the metal. The metal is cold and dew point is reached from within. That Batt insulation is a poor choice they allow inside temp to reach the metal causing condensation.

Just blow foam and be done with it. Ya want me to come and inspect it for ya. I will bring my Red Hat and give you one.;-);-):mrgreen:


I would have solid sheathing and good water barrier underlayment under that metal roof. I see problems with that j-box too.

:wink: That was the first thing I noticed.

ah, good catch. The JBox is temporary. There are going to be can lights where the Jboxes are. You’d croak if you saw the one with no jbox, just wires, wire nutted to a pigtail. :stuck_out_tongue:

Thanks, Charlie, I guess maybe the spray foam is best at this point. And you can come to WV any time. The wife is a GREAT cook! :wink:

That sounds like it will be even more interesting.:stuck_out_tongue:

You might want to let the roof remain a little wet. :mrgreen:

The thing that is causing condensation is the lack of an air/vapor barrier on the warm side, most of the suggestions above will work, closed cell foam is also an air barrier, and is probably the best option, (but what about off gassing UF?) 6 mil poly over the batt insulation (on the warm side) is the cheapest, it will also require some ventilation to the exterior, so that any air that gets in the batts and under the steel roof will be outside air.