OT: insulating metal building celing

JayinNY · Dec 5, 2011

My neighbor is putting up no faced insulation under the roof panales of his metal building, than putting Dow foam board up under the insulation. So looking up, it's foam board, insulation than the metal roof. I asked if the insulation was touching the roof and he said in some places it does. Do you think he will have moisture problems? He also heats the building!

Stephen Newell · Dec 5, 2011

I'm having trouble understanding your question. I have a pole barn with a dirt floor where part of it is not insulated. During cold and damp weather the roof literally rains inside the building from condensation. Other areas of the building I have vinyl faced fiberglass insulation and the ceiling stays dry except where I have fiberglass skylights. If I were using foam board instead of the fiberglass insulation I would put it between the rafters and the sheetmetal. The areas of my building that rain inside, the rafters are rotting somewhat from the condensation because the water runs between the rafter and metal.

paul · Dec 5, 2011

Some foam boards are moistureproof, some are open & moisture moves through.

If it's the right foam board, should be ok, but I'm no expert, just a general observation...

You don't want vapor moving through the insulation from the hot room to the cold side of it, the board better stop the moisture.

If enough insulation, the cold side of the insulation and the roof tin should be the same temp and no longer condense any moisture, so won't matter.

_Unless_ moiture is moving through from the hot side to the cold side....

--->Paul

Earl Gray · Dec 5, 2011

The corrugation of the metal should allow some ventilation, but the most important thing is to stop the moisture from getting into the building. There is a material called condensation stop that should be used right under the steel that should reduce the problem. I used scrap wet felt (like a heavy wool blanket) from a paper machine on ours and it works great. We also have the class 5 gravel floor covered with poly and then dryer felt.

Lloyd In South Carolina · Dec 5, 2011

I just put up a new metal buidlig, used a insulation that the metal supplier provided, foil on one side, white vinyl on the other, came in 6'x125'x 3/8" thick blanket like material. All the seams were peal off sticky tape, when done the entire roof was sealed. The metal sits directly ontop of this material.

This was recomended by the metal supplier.It was not cheap, $255 per roll.

L.

johndeerefan · Dec 5, 2011

They sell foam vent sheets you put against the metal for ventilation. They make a trough for the air to go to the peak. They use these on houses when the rafters or trusses meet at the wall where airflow gets blocked.

Chances are he might not have the rain effect in the building, but the insulation will become damp and may cause problems in the long term.

Carpenter once told me when building a house. "Build it tight and vent it right".

El Toro · Dec 5, 2011

One of my retired co-worker's has a big metal building and he had foam insulation sprayed on the walls and ceiling. I was over last March when it was still cold and he has an oil furnace
in there and when he turned that on it was very comfortable in there. It was tall enough and he built an office space in one corner. You need to climb steps to get up there. Hal

JayinNY · Dec 5, 2011

Ya I used those proper vents or whatever there called in my
attic, so there air could flow over and out. Oh well it's too late
for him to do that now

gene bender · Dec 5, 2011

It probably will sag and not touch the fiberglass but the condensation will be a problem shoulda put the foam board first.

OT: insulating metal building celing

JayinNY

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Stephen Newell

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paul

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Earl Gray

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Lloyd In South Carolina

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johndeerefan

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El Toro

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JayinNY

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gene bender

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