TOPIC: I Have An Existing Metal Roof and Have A Question
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We had a metal roof installed last June to replace a shingle roof that was well past its sell by date. The roofers took it down to the decking and installed the metal roof on that. The house was built in 1938 and we had lived here 12 years prior to the roof installation and had never had a mold issue in the attic. I went up in the attic last night to bring down a box and noticed white mold growing throughout the attic space.
As noted, this has to have something to do with the metal roof installation as it has never been a problem before. What can it be? Who do I need to contact in my area (Brownsville TN about an hour from Memphis) to find out what is causing it and then to remedy it? I have contacted my insurance agent to see if he can recommend anybody but thought I would ask here as well. I haven't contacted the roofer yet but I'm sure that when I do he will be slow to return calls of this nature. We thought a metal roof installation would sort our problems but it appears to only have created one-a huge one.
I desperately need some guidance here about what to do and how to proceed. I don't like this stuff flourishing in the attic!
I would connect with the installing contractor. Was the ventilation in the attic changed any with the new roof? It sounds like what you need is ventilation. Metal roofs can drop the roof deck temperature a bit and cause condensation that did not occur before but normally this only happens in situations with inadequate ventilation. I will also add -- if anything else has been done to the home such as new windows or siding, those things also made the house "tighter" and increased the need for attic ventilation.
I contacted the installing contractor today and he is supposed to come out tomorrow. They removed four layers of shingle roof material and went down to the bare deck. Nothing about the house has changed subsequent to the roof installation. It is definitely a post-roof installation issue. Something has fundamentally changed with respect to the ventilation/circulation in my attic.
The roof could have been inadequately vented previously, but warmer as a result of the shingles. A metal roof will get as cold as the ambient air temperature in this case which may be the reason that the interior is condensating where it didn't previously.
Thanks for that Eric.
I am hoping that the contractor shows tomorrow and then has an idea as to how to proceed.
Still waiting on the contractor.
When we had the roof installed we had them leave the two turbines that were on the house off to minimise holes through the roof. I am wondering now if this may have been a mistake on our part but it looks like the roofer would have advised us if it were.
That is a very dramatic change and likely would have caused condensation even if the roof had not been replaced. Good ventilation requires intake and exhaust vents, ideally a pretty even balance of the two. A good source of basic venting information can be found at www.airvent.com
Just an update.
The roofer came out and agreed it was a ventilation issue. He's proposed replacing the turbines. The reason we left them off was to minimise holes cut in the roof and improve the sightline of the roof--the latter being purely an aesthetic consideration. Would gable vent fans work just as well as the turbines? If so how large would they have to be? Or should we just stick with the turbines?
I also have a technician coming to check the house to advise on the mold's removal.
The gable vents likely will not move as much air as the turbines. They also will likely not create as good of airflow through the attic. All vents will carry an NFA (Net Free Air) rating which indicates a rating as to how much air can move through them. What you ideally want is a system that is pretty much evenly balanced in terms of NFA of intake (soffit) vents and exhaust vents. If the turbines worked before, then I would go back to that and hope it works now as well. As Eric and I both mentioned, a metal roof (plus removal of the old shingles) can drop the temperature of your roof deck, and that creates a challenge in that it increases the potential for condensation. So, we need the air movement to get the warm moist air from inside the home exhausted out. Looking for air leaks from the living space into the attic and sealing them will be helpful as well -- look for leaks around light fixtures, and also for things like bathroom, kitchen, and laundry vents that may be vented into the attic rather than to the outside.
Thanks for that Todd. The turbines were working before so, ugly as they are, I guess we will go back to them then.
Do the turbines really exhaust more air than the fans? I would have never thought but at least they don't have to wired into the electrics.
We have a technician coming in the morning for an estimate. I will need to call the roofer back about the turbine installation.
Also my attic space is desperately wanting in insulation in spots. A lot of it has compressed over the years and in places I noticed there was none. Presumably getting the insulation up to the mark would also help.
Also, this house doesn't have any soffit vents-never has-so I suppose I should look into that.
Thanks for the update. Proper ventilation requires intake and exhaust. I may have mentioned this earlier but a good source of ventilation information is www.airvent.com. Vents all have an NFA (net free air) rating that ranks how much air can move through them. The turbines will probably mean you can move as much air as can come in through the gable vents, at the speed driven by the turbines. Adding a power fan to one of the gable vents will limit you to how much air the other vent can allow as intake, again, limited as well by the fan speed. Gable vents also do not do a great job of mixing up the air in the attic though they do a decent job of taking advantage of convective (hot air rises) air flow in the attic. The turbines probably will perform better but are not easy to get watertight on a standing seam roof. I forget ... have you discussed whether a ridge vent could be added? (Likely pretty difficult at this point.) Chances are at this point you have very high moisture levels in your insulation. That really diminishes its effectiveness. As the insulation dries out, most of the original effectiveness will return. Still, more insulation is not a bad idea.
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