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  (Source: CBS)
National Association of Home Builders has promised an investigation into heat-glare from window treatments

Heather Patron of Studio City (Los Angeles, Calif.) accuses her neighbors of a dastardly crime -- melting her Toyota Motor Comp. (TYO:7203Prius.  No, really.  This was no Hawaiian Baby Woodrose-induced optical illusion, her neighbors’ energy-efficient window treatment had melted the plastic molding of her Prius' mirror housings.

Los Angeles is a seasonable southern city on the west coast.  Its average monthly maximum temperatures are historically confined to the 64-77 ºF range year round [source].  Unsurprisingly, the big concern for residents in terms of energy efficiency is the cost of air conditioning.  One of the major sources of heat entering the house is through window light.  So southern Californians, like residents of other longitudinally southern U.S. states, have taken to applying reflective windows treatments, both as a cost-saving measure and as a "green" energy saver.

But in this case the approach backfired, as the neighbors' energy efficient reflective gloss created a brilliant beam during daytime hours that directed itself directly at the car port.

"The side view mirrors were melting.  Anything that was plastic on the car was melting," the Prius-owner recalls.

Melting Prius owner
Ms. Patron shows offer her damaged Prius.  She claims her neighbor's energy-efficient window treatment did the damage.  [Image Source: CBS]

And Ms. Patron says her Prius wasn't the only ones damaged -- a neighboring vehicle saw similar melting.  She comments, "I'm positive that this window is what is causing the damage to my car.  I just don't feel like it’s fair.  I feel like it needs to be known that this is happening. And a lot of people probably have damage out there, that they aren't aware that it’s the windows that are causing this."

She claims to have measured the temperature in the car port when it's exposed to the beam and found it to be 120 ºF.

Studio City
The damage occurred in Studio City, a suburb of southern California's biggest city, Los Angeles. [Image Source: Google Maps]

Similar claims of reflective windows burning people or plastics were leveled in Sept. 2010 by a lawyer staying at the Vdara hotel in Las Vegas, Nevada.  Reportedly in that case the situation was even more severe as the reflective windows were acting as a hyperbolic solar dish, focusing sunlight into a "death ray", which swept across the pool deck.

Reportedly other homeowners have also complained about plastic-melting reflective beams coming off windows with certain energy-efficient treatments.  The National Association of Home Builders has promised a thorough investigation into this problem.

What makes Ms. Patron's story more curious is that automotive mirror housings are usually primarily composed of ABS (acrylonitrile butadiene styrene) [source] -- the same type of plastic found in LEGO blocks and plastic pipes.  Pure ABS has a melting point of 221 ºF [source], so it's unclear how the beam was able to melt the plastic, even if the air temperature was 120 ºF.  

One possibility was that the black mirror plastic absorbed the light, and heated up to a temperature far hotter than the surrounding air (think of an Easy-Bake oven).

Prius
The Prius is the best-selling hybrid electric vehicle in the U.S. (and in the world). 
[Image Source: Jason Mick/DailyTech]

The Prius is the best-selling hybrid electric vehicle in the world.  As of March 2011, 3 million Prius vehicles had been sold worldwide, with 1 million sold in the U.S. alone by April 2011. 

Source: CBS



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RE: Umm
By geddarkstorm on 1/26/2012 1:02:15 PM , Rating: 2
You just contradicted yourself. If in Phoenix it gets to 120F and cars don't have a problem even when uncovered (I'm sure people in Phoenix have Priuses) then that supports the idea the glare from the windows was the cause, by focusing reflected heat on the black plastic casing and greatly heating it above air temperature. Also notice, her car was in a car port, and thus "covered".

Additionally, this also happened to another neighbor's car, but I didn't see where that type of car is listed. Still, that increases our sample size. And we have previous reports of similar things.

It really isn't a surprise: heat has to go somewhere, and if you aren't letting it in, but reflecting it tightly, it's going to go right where you're directing it. Remember, you can't destroy energy.

The real danger is a fire starting; especially in the dryer summer months if one of these reflected heat beams gets focused on dry grass. How would they fix this? Just make the reflective coating of these heat mirror windows simply disburse the light rather than gather and reflect.


RE: Umm
By JediJeb on 1/26/2012 1:50:06 PM , Rating: 2
Problem comes in the shape of the window/windows. If they total surface reflecting is concave then it will focus the sunlight, if it was convex then it would disperse it. If you have a four window set on that side of the building say in a two by two arrangement and it happens that the corners of those windows which are nearest the center of the grid all are recessed into the building slightly then you have a concave mirror which would focus the light reflecting from them, if those same corners are protruding from the building slightly then you would have a convex mirror and the sunlight would not be concentrated into a smaller area.

Seems here there is just the right combination of window shapes, direction the house is oriented and relative position of the neighboring carport to cause some serious problems.


RE: Umm
By spread on 1/26/2012 2:33:31 PM , Rating: 2
quote:
Problem comes in the shape of the window/windows.


Not an easy fix. Probably double pane windows sealed with argon or nitrogen in between. How much they flex and what shape they take depends on atmospheric pressure and temperature of the gas (and how much it expands or contracts relative to outside air). They are sealed TIGHT to prevent moisture from getting inside as well.

I agree that this is not Toyota's fault. If they made high temperature plastics you know what happens? They become brittle when temperatures are low. And if you put softer plastics that are more flexible in lower temperatures without shattering, they melt in the Phoneix sun.


RE: Umm
By MrTeal on 1/26/2012 3:50:39 PM , Rating: 3
Here's a fun fact that applies more for a circular piece of glass but should be similar for a square: if a 48" glass flat is ground to a saggita (depth of arc) of 1/8", it would have a focal point about 100' away. It wouldn't be a perfect focus for a couple reasons, but you could get a lot of light concentrated into a very small area even with a fairly small curvature. The plate glass would probably never distort by 1/8", but I could a lot of energy being dumped into a black mirror.


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