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reflection damage on siding


John Dirks Jr
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This is the first time I found reflection damage on siding. My client asked how something like this could be prevented.

1: Change to a different siding product that doesn't melt when it gets hot.

2: Change out the insulated glass panel & hope that the new one doesn't go concave the way the first one did.

3: Install a barrier to block reflected light from that window to that section of siding. Alternatively, install a barrier to prevent sunlight from hitting that window at such an angle that it will be reflected to that particular area of siding. Plants, screens, & vegetation all work.

When you know the potential is there, what can you do to prevent siding damage due to sunlight reflecting off of windows?

If there's no damage, I don't say anything. It's hard enough to get people to believe that this can actually happen when the evidence is right there in front of their eyes.

- Jim Katen, Oregon

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Jim mentioned the concave pane. I understand how that can concentrate the light and heat.

In cases where siding is being melted, would you always need concave glass?

Will the sealed double panes flex in and out as they change temperatures, thus moving through cycles of more and less deformation?

I've read a number of pieces on this issue and have yet to see anything conclusive on the offending glass. Factors mentioned are low-e glass, thin glass, temperature effects on the airspace between the glass, time of year, and argon depletion. I've read of at least one case where newly installed replacement windows caused the problem fairly quickly, which would appear to rule out argon depletion as a necessary cause, but it sure is an interesting phenomenon anyway.

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Jim mentioned the concave pane. In cases where siding is being melted, would you always need concave glass?[/

All window glass is concave since it is annealed, and is affected by the Earths gravity during the process. The glass is further distorted by the location of the low E film (if it is on face 2 or 3 of the IGU).

Will the sealed double panes flex in and out as they change temperatures, thus moving through cycles of more and less deformation?

Yes

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That's a great place to install a shutter. 'Plastic' shutters are made of polypropylene and have much higher melting point than vinyl. They're also much easier to replace than the siding. Problem solved in fifteen minutes for around $50.

John, the problem is the glass. Most windows on the market are made with single strength glass that measures just over 1/16" thick. When the glazing area gets too large to be reliable, usually around 4 square feet for insulated glass, manufacturers switch to single strength annealed (Andersen places annealed only on the outer pane to reduce costs). Eventually the glazing area will get large enough to require double strength glass, and still larger units need to be tempered. Single strength and annealed glass are going to be more susceptable to collapse than thicker double strength and harder tempered glazings. The heat treating processes of annealing and tempering can distort the glass being treated, though I would think that the uniform ripple distortion of tempered glass would also prevent the fine focus that seems to exacerbate the phenomena, but that's just an educated guess.

Collapsed glass has alot of variables. Thin glazings contribute, but so does the thickness of the air space, the overall size of the IG unit, the type and placement of the low e coatings, and the spacer system used. I think this problem would disappear in large part if the window manufacturers would use double strength glass with a ridged spacer, an overall thickness of no less than 3/4", with the low e coatings on the inner pane of glass. The impacts on thermal performance and production costs would be minimal, about .03 shift in U factor and 3-5 cents per square foot of IG unit, the latter would easily be recouped with the reduced failure rates of thicker glazings.

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This is the first time I found reflection damage on siding. My client asked how something like this could be prevented.

When you know the potential is there, what can you do to prevent siding damage due to sunlight reflecting off of windows?

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Solar screens on every window including the neighbors and the school bus parked next door.

Or don't use cheap siding.

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I was sitting at my desk this morning and it hit me that this would be a good example of the reflective capabilities of low e glass.

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My computer screen is directly under that reflection off the interior of a high performance window sitting in front of my desk in the middle of my showroom. The source is passing through and being filtered by two high performance low e windows and two approximately 10' air spaces. Each window has a visible transmittance of about 55% (roughly half the visible light that hits the glass goes through it) and reflective coefficient of .60 or better (40% or less of the remaining spectrum passes through). The light reflected in the photo has been roughly halved at each of the three low e units.

That should put a little perspective on how much energy is involved in this phenomena.

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My computer screen is directly under that reflection off the interior of a high performance window sitting in front of my desk in the middle of my showroom. The source is passing through and being filtered by two high performance low e windows and two approximately 10' air spaces. Each window has a visible transmittance of about 55% (roughly half the visible light that hits the glass goes through it) and reflective coefficient of .60 or better (40% or less of the remaining spectrum passes through). The light reflected in the photo has been roughly halved at each of the three low e units.

That should put a little perspective on how much energy is involved in this phenomena.

Here's what I got from all that: you're being paid to post on TIJ

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My computer screen is directly under that reflection off the interior of a high performance window sitting in front of my desk in the middle of my showroom. The source is passing through and being filtered by two high performance low e windows and two approximately 10' air spaces. Each window has a visible transmittance of about 55% (roughly half the visible light that hits the glass goes through it) and reflective coefficient of .60 or better (40% or less of the remaining spectrum passes through). The light reflected in the photo has been roughly halved at each of the three low e units.

That should put a little perspective on how much energy is involved in this phenomena.

Here's what I got from all that: you're being paid to post on TIJ

Kewl!

Hey Tom, ask whoever is paying you whether Mike and Rose and I can be added to the payroll.

ONE TEAM - ONE FIGHT!!!

Mike

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Part of my day job involves sitting at a desk essentially waiting for someone to walk in the door or for the phone to ring. Usually it's only a very small part of my day; 30-40 minutes in the morning, lunch at my desk(that is frequently interrupted), and 20-30 minutes in the afternoon. Today it was by design. The boss and his wife (the office manager) are on their way to the remodeler's show, one of our salesmen is on vacation this week and it is another's scheduled day off. Poor planning on their part has me scheduled for seat time with precious little to work on, so I'm hangin' here. If I had a report to write I'd be doing that instead. I'll probably do an RRP module or two after lunch.

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Part of my day job involves sitting at a desk essentially waiting for someone to walk in the door or for the phone to ring. Usually it's only a very small part of my day; 30-40 minutes in the morning, lunch at my desk(that is frequently interrupted), and 20-30 minutes in the afternoon. Today it was by design. The boss and his wife (the office manager) are on their way to the remodeler's show, one of our salesmen is on vacation this week and it is another's scheduled day off. Poor planning on their part has me scheduled for seat time with precious little to work on, so I'm hangin' here. If I had a report to write I'd be doing that instead. I'll probably do an RRP module or two after lunch.

Start making cold calls or grab a broom, mister! [;)]

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  • 1 month later...

I ran into this yesterday, and I'm having a hell of a time writing about it. The pics don't show the damage clearly enough to bother posting.

The diagonal pattern was there, the south facing windows from the house across the driveway, the whole setup was perfect.

How would you write it without proof, without starting a war between neighbors, and ultimately ending up in a world of crap over it?

It walks like a duck. It quacks like a duck.

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I ran into this yesterday, and I'm having a hell of a time writing about it. The pics don't show the damage clearly enough to bother posting.

The diagonal pattern was there, the south facing windows from the house across the driveway, the whole setup was perfect.

How would you write it without proof, without starting a war between neighbors, and ultimately ending up in a world of crap over it?

It walks like a duck. It quacks like a duck.

I had the opposite situation earlier this year. The house I was inspecting had been damaging the neighbor's siding.

I've attached that page from my report to show how I dealt with it, if that helps.

My approach is to just tell them what's going on.

- Jim Katen, Oregon

Download Attachment: icon_adobe.gif Melty Vinyl.pdf

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Thanks, Jim.

My problem is, it was pouring out. At least you were able to show what was going on.

Here's what I have so far.

"The vinyl siding on the northwest side of the home is deformed in a diagonal pattern that looks like the same pattern known to occur as a result of thermal distortion caused by the reflection of radiant heat.

Because of the weather conditions at the time of the inspection, I was unable to confirm this was the cause."

Tear it up. Fix it. All are welcome.

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