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Blackened Wood Windows 2


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I have broached this subject before in another post. I have to assume most HIs are seeing the same thing again and again on newer clad windows. I know I have. Mike O. has called it incipient rot.

These are 13 yr old wood sashes with an aluminum cladding at the exterior. Probing the black areas all around the sash edges shows no rot but does this mean there is rot deeper beneath - closer to the exterior cladding? Or is there no way of knowing without prying at the exterior cladding?

What is your boiler plate for this problem?

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The last photo, in particular, looks to me like condensation is forming on the window. Look at the gray coloration on the lower part of the interior frame. If it's solid under the window I can't see how there's a big problem with internal rot. Every metal-clad rot damaged window I've seen is soft on the bottom.

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Most of that damage is from condensation, but that doesn't mean there isn't more damage you can't see.

First, look at the 'gasket' around the glass. It's called a marine glazing boot and it's a U shaped channel that goes around the edge of the IG (Insulated Glass) unit. To keep condensation from pooling in it and degrading the IG seal it is perforated along its length and has big gaps where it is cut to bend around the corners. All of the condensation that occurs at the edge of the glass either spills onto the surface or is dumped into the groove plowed in the sash rail to accept the glass. All the water dumped into the sash has to migrate through the wood to dry and vapor drive takes much of this to the back of the cladding. Marine glazing is cheap and easy to manufacture so it is prevalent on builders grade windows. Think Malta, Crestline, Craftline, Vetter, Caradco, LP, etc.

Second, look at the glass. The airspace is thin. They might be low E, but they would be made with cheap old tech coatings, and the slight airspace means little or no argon. Or they might be plain old Insulated Glass. Either way they are inefficient by today's standards, which means there will be more condensation.

Now look at the weather seals. You can't see any in your pics but there are typically two in windows like that. The one around the perimeter of the sash is called a dust shield because it's primary function is to keep debris out of the concealed hardware. It provides very little in the way of draft protection. The second is on the frame and it is typically a very small hollow bulb or a tiny vinyl fin. Neither is very effective and there tends to be large gaps at the corners. They seal just well enough to allow water vapor to condense on the glass rather than escape to the outside. Some small condensation events can actually be resolved by simply unlocking the windows, loosening the weatherstrip enough to allow the moisture to escape before it condenses.

Finally, look at the cladding. On most of the windows I mentioned above the cladding is roll form aluminum (think seamless gutters, but much thinner) that gets clipped onto the wood sash rails and held in place with adhesive. In order for the rails to fit together the corners of the cladding are loose enough to slide past one another, which is loose enough to let wind and water and other stuff in too. The adhesive is a vapor retarder and we all know what vapor retarders do. When you see one of these windows with loose cladding it's usually because the wood has rotted out from behind the adhesive, often long before they look like the windows in your pics.

Now you understand why thy look like they do. Use that information to identify builders grade products and advise your clients that these things have a life expectancy of 15 years or so. They can spend lots of time on maintenance or replace them at regular intervals. Premium wood window products have much better water management details and may last 20-25 years.

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Now you understand why thy look like they do. Use that information to identify builders grade products and advise your clients that these things have a life expectancy of 15 years or so. They can spend lots of time on maintenance or replace them at regular intervals. Premium wood window products have much better water management details and may last 20-25 years.

The wood products in my house must be super duper premium; they're 160 years old.

I'll admit they require maintenance every 30-50 years.

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That's old growth timber. It's more robust. The windows are drafty enough that the dew point is several inches outside the house until the glass temps dip below 30 and condensing vapors skip the liquid phase and go straight to ice. And, when the sash exceed their carrying capacity they shed their paint so they can dry.

When we run out of white pine and start making windows out of plantation trees you can cut my service life estimates in half.

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... these things have a life expectancy of 15 years or so.

That's too bad.

Interestingly, studies in England show AL clad timber windows to have a life expectancy of about 45 yrs. The NAHB estimates less than half that.

LIFE CYCLE OF WINDOW MATERIALS - A COMPARATIVE ASSESSMENT

http://www.cibse.org/pdfs/Masif.pdf

Report for the Wood Window Alliance, June 2013.

http://woodwindowalliance.com/medialibr ... %20LCA.pdf

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20 year old wood windows in my "dry" climate. total of 10 on this house. Some so bad that the framing underneath is rotted and the siding is popping off from under the windows. I agree that some of that shown above is just condensation stains but that stain is a form of fungi. You can have rot there and not even realize it. When I opened the windows in the photos below there was rot in the sills that couldn't be seen from inside or outside unless the windows were opened.

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It is not just happening with the little window companies

http://www.windowsettlement.com/Default.aspx

I have recently seen 13 yr old Norco (Jeld Wen) windows rotting out. Since total house window replacement can run $20K to $40K it would be prudent for HI's to check windows very carefully.

About 10 years ago I received a call from an angry client who had about five sets of windows where the sashes were turning into sponges. He wanted me to replace them. This was 23 months after I had done the inspection on his house and I told him I would do no such thing. He told me he was going to sue me but nothing ever came of it. Anyway, I learned a lesson to not take the window inspection part of the job lightly.

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