question??? Metal roof sweating

A customer of mine is asking for your help!: said his 18x50 warehouse roof is sweating with condensation inside the building.

It is a metal (shed type) roof with what sounds like aluminum backed insulation. not sure of thickness.

Floor to roof is open like a cathedral~ with 2 partitions making 3 separate rooms ( like a stall)
he says this never happened before. I asked him what changed. he said he installed a vent-less heater system thats when the problems happened. (now its a heated space)

So any ideas. this is open for discussion.
Thanks in advance.
Matt from Johnson Home Inspection. :shock:


The word’s “vent-less” implies that it’s a gas heater system. One of the by products of gas combustion is water vapor. My guess is that the mositure from this heating system is in the building, and condensing on the colder surfaces.

I don’t know if the vent-less sytem has an option to actually install a vent or not. If so, that’s what I would try first. If not, then I’d try a de-humidifier and see if that helps.

Others may have some other/better suggestions…that just my quick two second conclusion.

Hope it helps.

He’s got heat inside (ventless is the worst), and snow outside. The condensation is dripping because there’s no barrier between the heat and freezing cold snow build-up on the metal roofing.

Vent-less are not approved in many areas including Canada.
I think all instructions say they must have a window open to let in air.
I do not think they are approved as the only means of heating.
There has been considerable discussion on the NACHI site about them .
They use up oxygen and give of Moisture.

Thank you both for your input. I poersonaly have not seen his set up yet, but I am looking forward to it. also I apreciate the input on the ventless heating systems.

Matt …I have a vent less gas stove as an alternative heat source in a 3 season room at my home …the room also contains 12 large hi-efficiency windows…the vent less gas stove is a fast and effective way to get a lot of heat fast in case of a power failure but the colder it is outside the wetter the windows get while it is in operation…You would think there was a swimming pool in that room when it is operating …i think You can be pretty certain that is where your customers condensation troubles are coming from…

Excelent info All. I will forward this info to my customer. I apreciate the input a lot.