We’ve noticed some mold on one side of the peak of our cathedral ceiling. The roof has baffles under the sheathing going from soffit to ridge vent, then blown-in cellulose insulation. The interior finish is Armstrong – the stuff that looks like wood, but isn’t – can’t remember the exact product name. Based on some of the other issues we’ve had in this house, I’m not going to assume that any of this was installed properly. We also have a major draft coming in, but haven’t been able to pinpoint where.
This is a vacation home, so when we’re away the temperature is set back pretty far. There’s no air conditioning, so the moisture level inside during the year is pretty wide-ranging. Not sure if either of these is contributing to the problem. I haven’t noticed any leaks in the roof, and the “wood” ceiling isn’t bubbling or warped – just the mold. So…. we need help in trying to figure out the source of the mold, and what to do to correct it.
Any help is appreciated, and let me know if more info is needed. The contractor (I’m being generous here) isn’t in business anymore, but I can probably figure out any missing info.
Thanks!
Replies
How do you know it's mold, vs moisture staining or efflorescence?
Luna
Is there taped drywall behind the Armstrong faux plank?
are there any penetrations in the ceiling (cans, ceiling fans, other)?
thanks
No, there's nothing behind the Armstrong. There is a ceiling fan at the peak. The "mold" area is to one side of the fan, and right at the peak. I tried to get a couple pictures, so hopefully that helps.
As to whether it's mold or something else, I won't know until I can get all the way up there, but it looks like mold as far as I can tell. I need to buy two more sets of scaffolding because, of course, the area I need to reach is right where the loft ends. We'll have to put three sets in the living room, one in the loft, then use one to bridge them. Ugh.
Yeah, does look like mold, though it could be some sort of chemical thing going on. (Kinda weird that the stuff would so readily support mold growth.)
Those kinda look like drip lines running cross-wise on the planks (up and down on the ceiling). Are they drip lines or part of the wood pattern?
Took me a minute to see what you meant, but I think you're seeing the end joints. The ends of each plank have a slight bevel.
I'm going to head up to the roof and double-check the ridge vent in a bit. I thought my better half had already done that, but I was mistaken.
No, I'm seeing streaks run across the planks, at right angles to the grain, every couple of inches. They aren't quite vertical but seem to run slightly diagonal.
OK, I see -- there are some right below the light -- 3 lines. And then in the plank down 2 from there the exact same pattern repeated, so I guess they're fake tool marks.
Is that stuff covering the (strange looking) cells solid plastic, or is it netting?
You Have Good Eyes
I missed the 'tool marks', but see what you mean now. There's netting over the blown-in insulation.
I went up onto the roof. Never want to do that again!! Whose crazy idea was it to make the roof 10/12? Anyway, I couldn't really see anything without pulling up the capping shingles, so it was hard to see what was going on underneath. What I could see was a layer of what looked like fabric embedded with hair from my dog. It runs parallel to the vent. It didn't seem to be attached to either the roofing shingles, or to the vent, along the outer edges, but I'm supposing that it's attached to the vent somewhere inside.
In one section, the roofing shingles started where the ridge vent ended, and I could see the nail holding it in place. It appears as though there's another shingle underneath that one - but they're obviously lapped wrong. Surprisingly, this wasn't the same area of the roof as where the mold is, though it seems to be close.
Looks like mold to me.
My guess is that warm, moisture laden air is condensing on the surface of these planks and microrganisms are feeding on the surface finish and/or dust. The mold condition could be deeper, but hard to say without probing or invasive techniques. My guess is that the mold mostly propogates when it is very cold outside and lack of proper insulation/air infiltration allows a dew point temperature to be reached at the ceiling surface.
You might want to check the surface of your ceiling finish with a laser thermometer to see what kind of differences you are getting in certain areas during times of extremely cold temperatures outside. You might also want to check the moisture content of the ceiling materia itself with a moisture meterl. Most decent moisture meters have setting for building materials other than real wood.. YOu'll also probably want to investigate the answers to the following questions:
1. What is the R-value of your ceiling insulation and is that value code and consistent?
2. What is the temperature and relative humidty in your second home when it is occupied and unoccupied?
3. Do you have the mechanical means with which to change moisture conditions that can will avoid conditions for propogating mold spores?
4. Could wind washing be reducing the effective R-value of your fiberglass insulation.
Yeah, basically it would be just like moisture condensing on a windowpane.
it can be very difficult at times to see if there is a "leak" from examining the top side of the roof. If you have not obvious evidence of a leaky roof causing additional moisture then you should keep your heat on at a higher temp when not there.
It looks and sounds like mold due to high levels of humidity. Your heat will help keep those levels down, if heating the place for prolonged periods is to costly then you should consider a dehumidifier.
Note that if there were a leak you'd probably see more evidence of water staining, and there would likely be some warping of the planks.