Drip stop membrane on metal roof/purlins needed with vinyl face insulation?

tlmartin84 · Oct 2, 2014

My metal roof is on purlins, I have always been under the impression that as long as there was a good vapor barrier (vinyl faced insulation) between the heated shop and metal roof there would be no condensation.

The metal guys are trying to sell me on metal that has a layer of essientally foam film on the backside that reduces condensation. Is it needed?

Hoping some of you all with metal roof/pole barn setups can comment......

maynard9089 · Oct 2, 2014

I have it on my new building and so far so good. I don't believe it added much cost, looks good and has worked as it was advertised. The building is uninsulated right now and its in the high 70's during the day in full sun and into the 40's at night. Glad I used it.

readhead · Oct 2, 2014

You said it yourself, "reduces condensation". It all depends on how much moisture is introduced into your building. The more insulation, the less condensation. Air movement will help but unless you can change the air for colder outside air you won't reduce the moisture and of course now you are loosing heat.
Short answer, reduce moisture and add insulation. Another way to say it is "control the dew point".

tlmartin84 · Oct 2, 2014

I can deinately see it being needed if there is no insulation, but with Vinyl Faced R30 is it needed?

Don't a lot of guys just put in insulation with the fiberglass part right against the steel and the vinyl face down? .......... with no issues?

It is going to be an extra $1000.

readhead · Oct 2, 2014

If you are already doing faced insulation you don't need the extra on the sheet. If you are doing R30 it will be in two layers. Usually a R11 faced over the purlins loosely and then an unfaced R19 running between the purlins.

Leaflessshadetree · Oct 2, 2014

The coating doesn't reduce moisture (or condensation). It does hold the moisture and keep it from collecting thus reducing water dripping from condensation.
I used it for my roof and it seems to work well.

readhead · Oct 2, 2014

Leaf. Not trying to be a smartass but how do you know?

Rookie2 · Oct 2, 2014

anyone have a product name, can't find any by doing a search . sounds promising but suspect !

volleyball · Oct 2, 2014

I have the old shingles under mine so it is no concern. But I thought that the pitch of the roof metal would make the condensation if there is any run down and off the outside edge.

maynard9089 · Oct 2, 2014

http://dripstop.net Is the stuff my metal came with

Leaflessshadetree · Oct 2, 2014

readhead said:
Leaf. Not trying to be a smartass but how do you know?

How do I know it works? Pretty easy. On cool humid mornings with a heavy dew. The concrete floors and anything metal in my garage and shed will be wet (actual water droplets). I can actually see water beading and running along the underside of the roof and dripping from the metal roof in my neighbors shed.
The floor in the shed with the condenstop barrier will be moist and if you go up and feel the underside of the roof it feels like a damp sponge. That building dries faster and the condenstop will be dry that same afternoon.
BTW: None of these buildings are insulated at this time.

readhead · Oct 2, 2014

Thanks. From the info I have read that is what it is supposed to do, stop the drips. Sounds like a good solution in an uninsulated building. I have never erected an uninsulated building here.

volleyball · Oct 2, 2014

When I did my shed, I put 1/2" blue foam board under the metal mostly to deaden the sound of rain. It has practically no pitch. I get no indication there is moisture collecting on it. Maybe I am smarter than I think.

Drip stop membrane on metal roof/purlins needed with vinyl face insulation?

tlmartin84

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maynard9089

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readhead

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tlmartin84

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readhead

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Leaflessshadetree

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readhead

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Rookie2

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volleyball

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maynard9089

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readhead

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