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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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How is reflected light concentrated?
By dgt224 on 1/26/2012 2:14:30 PM , Rating: 2
I don't think I've seen a condominium with windows that appear concave from the outside, so presumably the reflected light would be no more intense than direct sunlight. In fact, it would ordinarily be less intense, as energy-efficient windows are designed to pass a fraction of the light, at least in the visible spectrum, and reflect the rest - otherwise a sheet of plywood would work equally well and be a lot cheaper. So it seems likely that the reflected light from the window strikes the car at a time when the car is also exposed to direct sunlight; doubling the effect of solar heating might well be enough to cause ABS melting.

If that is the source of the problem, I would also expect to see some damage to plants on the ground that are exposed to light reflected from the window and to direct sunlight at the same time - any light source capable of melting ABS should also do detectable damage to most living plants. No indication that anyone has looked for that sort of damage, though.




By JediJeb on 1/26/2012 5:16:02 PM , Rating: 2
Only a very slight curvature is needed to focus the light that is reflected, or multiple windows with slightly different angles could also act to focus the light.

It also looks like the doubling effect would not come into play since the carport is shading the mirror from overhead sunlight.


"Young lady, in this house we obey the laws of thermodynamics!" -- Homer Simpson














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