Need Advice for Mold in Attic!

I have just discovered some mould in my attic on the inside of some of the roof sheathing boards. This is new … almost certainly in the last year or two. House is 36 years old. Roof has a 12-12 pitch with about 8’ sloped ceiling with dormers. Located near Ottawa Canada.
Two years ago we had a steel shingle roof installed. We opted for a continuous ridge vent and closed off the multiple mushroom cap type vents we had always had. The ridge venting is a continuous plastic tubular material (Quarrix product) under the ridge shingles with a strip of the top sheathing board having been first removed from each side of the ridge board.
One year ago I added additional insulation to the attic. Blown in cellulose on top of the original fiberglass batts. l was careful not to block the foam baffles between the rafters in the sloped roof. I did not notice any mold at this time. The soffit has a continuous aluminum vent strip front and back, not blocked. Nothing has changed on the inlet air side since the house was built.
Most of what I read indicates ridge venting should work well… and adding other types of exit venting to this is not a good idea. Im considering blocking off the ridge vent and adding 2 or 3 maxi vents.
Once I get the mold removed I need to be confident it won’t return.
Any other thoughts or suggestions??
Thx
Garth

Heavy condensation from the metal roof
Or the ridge hole is too wide.

Do you have a dryer or bathroom vented into your attic? Any obvious signs of leaking, waterlogged or rotting wood? There should be an underlayment that would prevent transfer of condensation.

Even if water cold not get thru the underlayment, the condensation could happen with the temperature difference between the house and the roof.

In theory it’s possible. I haven’t come across this just yet. Have you seen this happen? I am referring to metal roofs only. I have seen similar condensation in asphalt roofing caused by poor ventilation. But, have you seen an increase in condensation on interior attic ceilings due to metal roofing?

Condensation is very possible, especially in Canada where you can severe cold. Check your insulation and make sure the soffit vents are not closed off by the blown in insulation. Should be baffles there. Sometimes, it is just a result of the severe cold unless you have everything perfectly insulated.

Mix some bleach with water and spray it several times. If there is no moisture to feed it, the mold will die and not return. Keep an eye on it. Likely not something to panic about but watch it.

Nothing vents into the attic. Plastic vapor barrier on inside of ceiling insulation may not be 100%, but has not changed whereas the mold is new. thx.

“Check your insulation and make sure the soffit vents are closed off by the blown in insulation.”

I’ve never heard of blocking off soffit vents with installation. How exactly does reducing air flow help reduce condensation? Is this a typo?

I suspect this rrefers to 'access to" the soffit vents, via the insulated sloped section.

Intake vents frequently get blocked/plugged by blown in insulation.

One of the primary purposes of ventilation is to remove moisture from the attic space.

Ventilation is not there to keep your shingles from “baking”, that is an industry wide falsehood cooked up by manufacturers with the intention to cover for bad organic shingles.

Plz stop with the little internet wars.

I was actually asking a sincere question. I thought AD’s response was likely a typo. I probably should have pm’ed him about it? I didn’t intend this to be rude.

I agree with you completely. Assuming it was a typo. I agree with AD as well

It was a typo. I post a lot using an iPad, it sometimes has a mind of its own.

I post mostly on my phone. That’s why I have to edit pretty much all my post. I know I have seen your username before, AD. Do you post on any body building forums? I stalk those frequently trying to turn my keg into a 6 pack. Heck, I’d settle for a pony keg.

I don’t post on any body building forums.

That’s too bad…it would have been nice to get advise on roofing and the best brand of protein shake on the same forum! :wink:

Dairy Queen chocolate malt is my favorite protein shake.

Hahahahahaha! Touche’