Dear Readers,
Today I was removing kraft-paper-faced fiberglass bats from between the rafters behind my kneewall (cape cod house). They were draft with no signs of water stains. When I pulled the fiberglass bats away from the roof deck, there was frost on the roof deck and some frost on the bat as well (25 deg was high temp today). I've no idea how many years this may have been happening. I let it dry, but looked like mold so I sprayed Tilex (chlorine bleach & water mixture). After it dried, some of the white stains disappeared, but the dark stains still remain. Is this just stained wood, or ??? I can't imagine mold living after Tilex.

Before
http://i899.photobucket.com/albums/a...psb30b76b6.jpg

After
http://i899.photobucket.com/albums/a...psb0c50e0b.jpg

Comments appreciated.
Regards,
Theodore

On Sun, 27 Jan 2013 21:11:47 -0800 (PST), wrote:

Dear Readers,
Today I was removing kraft-paper-faced fiberglass bats from between the rafters behind my kneewall (cape cod house). They were draft with no signs of water stains. When I pulled the fiberglass bats away from the roof deck, there was frost on the roof deck and some frost on the bat as well (25 deg was high temp today). I've no idea how many years this may have been happening. I let it dry, but looked like mold so I sprayed Tilex (chlorine bleach & water mixture). After it dried, some of the white stains disappeared, but the dark stains still remain. Is this just stained wood, or ??? I can't imagine mold living after Tilex.

Before
http://i899.photobucket.com/albums/a...psb30b76b6.jpg

After
http://i899.photobucket.com/albums/a...psb0c50e0b.jpg

Comments appreciated.
Regards,
Theodore
Wait and see what it looks like when it is fully dry. Doesn't really
look like mould to me from here. Looks like wet wood - possibly with a
bit of rot? Is it soft where it is dark????

On Monday, January 28, 2013 12:11:47 AM UTC-5, wrote:
They were draft with no signs of water stains.
Meant to say "They were DRY with no signs of water stains."

The tilex is going to dry out a lot faster than the wood will. That's because the tilex is just on the surface of the wood, whereas the moisture in the wood has had the time to penetrate into the wood cells, and it takes a lot longer for water to evaporate through the wood cells walls than it does for Tilex to evaporate directly into the air.

That just looks like wet wood to me as well.

Really, what you need to do is scratch at that wet wood with your finger nail. If you can scratch that wood away with a fingernail, it's rotted. Otherwise, it's fine. Wood, being a natural material, stands up to occasional wetting much better than most building materials (like plaster or drywall).

I wouldn't bother with Tilex. I'd spray bleach straight out of the jug on that wood to kill any mildew or mold that might be there.

You can avoid further wetting of that wood by providing for an air gap between the insulation and the roofing boards, and allowing cold outside air to get in at the eves of your house, and out through a ridge vent along the ridge of the roof. The idea here is that the unavoidable heat loss through your insulation drive a convective air current from the eves to the ridge vent. That convective air current dries out any frost or condensation that forms on the underside of the roof.

The other side of the argument would be: If the house is 50 years old (I'm thinking because they used lumber for the roof sheathing instead of plywood or OSB), and there's no wood rot, then why not put the existing fiberglass insulation back in, and we're good for another 50 years. And, I would have difficulty giving a good reason NOT to do that. Millions of houses across North America don't have any roof ventilation at all, and yet most of them never have any serious problems with wood rotting in their roofs.

On Monday, January 28, 2013 2:12:09 PM UTC-5, nestork wrote:
.. -- nestork

Nestork,
Thanks for reply. Yes, I took a scraper to it and most scraped right off. It felt/looked/acted like a thin layer of rotten wood. This roof is on the north side of the house. My intention in this work is to air seal the attic and ventillate the deck as it's currently without any soffit vents. I understand your comment on leaving it for another 50years, but previous owner never lived in upstairs for all that time and it can get pretty hot/cold in summer/winter so I'm trying to be meticulous in my air sealing.
THANKS SO MUCH for your insight and opinion.
Regards,
Theodore.

Theodo

If you're wanting to convert that attic into living space, then consider replacing that fiberglass insulation with 2 1/2 or 3 inch thick slabs of extruded polystyrene foam.

There are two kinds of polystyrene foam; expanded and extruded. Expanded polystyrene foam is the stuff that looks like it's made of "beads":



Extruded polystyrene foam is most commonly blue or pink in colour and is sold under the trade names of Dow "Roofmate" or Owen's Corning "Pink" polystyrene insulation:



Not only does extruded polystyrene foam have an R value of 5 per inch, compared to about 3.5 for fiberglas and 4.5 for expanded polystyrene insulation, but since extruded polystyrene foam is impermeable to air, humidity can't get into it and condense into water or freeze into frost. So, extruded polystyrene foam is it's own vapour barrier and doesn't require that polyethylene vapour barrier sheeting be installed over it.

Both Dow and Owens Corning make all kinds of metal channels that nail or even staple onto the sides of the rafters to hold the foam panels in place. You caulk around each panel with expanding foam (like that Great Stuff stuff) and then trim off the excess expanding foam before installing your drywall. In this way, you establish an air gap between the insulation and the roof decking from the eve to the ridge.

Extruded polystyrene foam is more expensive than expanded or fiberglas, but it will pay for itself in energy savings in both summer and winter.