Michelle Melton
1/13/2014
We had a metal roof installed this summer. At the first snow this winter, we noticed the plywood in the attic was wet. It seems to be condensation, since it was fairly uniformly wet over all areas of the plywood. Now mold is growing on the plywood already. The house is 960 square feet, so it is a small home. We run a wood stove for heat in the winter, along with a supporting heat pump. We have a drop down door/ladder to access the attic, with a small area floored for storage. We have blown insulation along the floor of the attic, along with rolled insulation on top of that. We have soffit vents that run along the edge of the bottom of the roof, and a ridge vent that runs along the top. We do have a bathroom fan that is vented directly into the attic (which we have now learned is a mistake). When the metal roof was installed, they removed the asphalt shingles, put down tar/felt paper and then the metal. The condensation only seems to appear when it snows, and there is snow sitting on top of the metal roof. We have researched possible causes and have found a lot of information online, making it difficult to discern what the cause actually is, and therefore how to begin to try to fix it. Our primary issue with much of the information about ventilation and sealing off the living space from the attic to prevent moisture from getting up there is that the condensation never occurred with the asphalt shingles. It only began with the addition of the metal roof. Our roofer said he had never seen anything like this and could not provide any information on what might be the cause or how to fix it. We have talked to some energy efficiency people who said we need to seal off the living space air tight from the attic to prevent the moist air from getting up there. But we live in a climate that is extremely humid, so the outside air coming in through the soffit is already moist. And the condensation only started with the installation of the metal roof. We have found lots of information online about causes and solutions, but feel like we're not sure what is the most likely issue and fix and could really use some help with finding the best course of action to take. We're not sure if the roofer did something incorrectly and just does not want to deal with it, or if it is a separate issue altogether. Any help you can provide would be most appreciated!
Todd Miller
Classic Products, Inc.
1/13/2014
This very much sounds like a situation where the metal is transmitting cold to the roof deck and it's just enough to hit dewpoint, causing condensation in the attic. I do not run into this often but I have on occasion. Solutions include increasing ventilation in the attic (or making sure the current ventilation is working). You can test for airflow in the attic using a smoke pen or even a light piece of tissue paper held near the ridge. Reducing the moisture level in the home would also be helpful. And, of course, that bathroom vent needs to be vented outside. Now, sealing off the living space is also a very good idea but, if you have insulation down and no vapor barrier, it's hard to do that 100%. Sealing around your attic access would be good. Using an oil base moisture resistant paint on ceilings and walls would also be helpful. But, for now, I'd check the ventilation, vent the bathroom vent to the outside, and see if moisture levels inside the home can be dropped perhaps by a dehumidifier.
Info @windowsonwashington.net
An informed customer is our best customer.
1/14/2014
The air entering the attic in the winter months is not moisture laden and certainly not with enough that would create a condensation issue in the absence of any other moisture. You have, as Todd indicated, two things going on. 1. Too much moisture (via air leakage and bulk directed air via bath fan) getting into the attic. The attic floor needs to be air sealed and properly insulated and the bath fan needs to be vented to outside of the home ASAP. 2. Not enough ventilation. The second part of the equation might take care of itself if the moisture is reduced but you need to check that the soffits are open and the ridge vent is unobstructed.
Guest User
8/3/2017
I lived in Valrico, Florida located 45 minutes from Tampa, wanted to ask about metal roofs. I currently have a solar fan installed in our roof and is all covered with NASA aluminum for AC efficiency and keep the house cooler. This new installation reduced our electric bill almost in half and $100 less in the summer. Now we are exploring replacing out roof and would like to know the benefit of metal over shingle. Have read about it and to many contradict opinions about the matter. Would like to hear from experts on the field.
Todd Miller
Classic Products, Inc.
8/3/2017
Alma, I do not usually do this but, since you are seeking energy efficiency, I am going to give you a link to an article I have published on my company's website about energy and metal roofing. https://www.classicmetalroofingsystems.com/blog/energy-metal-roofing/ Other than that, metal is known for its resistance to the elements, its durability, its fire safety and low weight, and its ability to add curb appeal and value to a home. Please let us know if you have additional questions.

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