Ceiling Mould & Attic Insulation

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Posted by: from Vaughan
11/25/2011 at 11:15:39 AM

Our house is a semi-detached two storey house. We added some insulation in the attic early last year (2010). Some mould appeared on the ceilings of the corner of one bedroom from last winter. It got our real attention recently when the mould spread to another bedroom, all along the ceiling edges near the outside walls.

I'm not sure whether it's because of improper installation of the attic insulation? Or it's kind of the natural result since the house is sealed better than before, with more insulation at attic and also a replacement of the patio door and windows?

Thanks a lot!

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Date/Time11/25/2011 at 12:35:57 PM

Hi Qiong,

This is just a guess but when you added the insulation, you probably covered the soffit vents and stopped the air circulation in the attic. You should have baffles on the underside of the rafters that extend down to the soffit and allow air to come up and out the top. This air circulation carries away any water vapour before it turns into condensation. It is the condensation that is running down the rafters and dripping onto the insulation and then coming through onto your ceilings and is causing the mould.

It is possible that you have tightened up your house enough that it doesn't breath like it used to and eliminate water vapour. In that case, you did a great job!

A temporary solution is just to crack a couple of windows 1/16" to allow a little air to move. A better solution is to install an ERV (energy recovery ventilator) and continuously circulate the air in your whole house through it.

Good luck with it!

Jim Kuzma

Kettleby Handyman Services

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Date/Time11/29/2011 at 1:09:45 PM

Hi Qiong,

Jim is 100% right.

But you should be removing the area's affected by the mold and replacing it. Once mold starts it keeps growing, it's spores go every where and have been circulating through the house. Change the affected area, and get a couple new furnace filters to replace over the next few months. It's pretty damp this time of year, and dark, dampness is growth heaven for mold.

Do you hear any weird noises at night in the attic? A critter could have also opened up an entrance in your roof for a nice well insulated winter hide out. This is the time these little critter's plan for winter and I have run into this situation in the past.

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