Print 53 comment(s) - last by The Raven.. on Jan 30 at 1:07 PM

  (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).

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 JasonMick on 1/26/2012 12:53:38 PM , Rating: 5
Was just about to say that. In Phoenix, it would get to 120F. Generally at that point we just cover the cars but cars left out don't usually have this issue. It's the plastic, not the windows.
True, but that's 120F AIR TEMPERATURE. Thus your heat transfer problem is a matter of convective heating.

By contrast here you have semi-direct solar radiation .

I'm guessing if the owners aren't faking this, then any black plastic ABS car mirror would see similar melting. Toyota's mirrors aren't exactly special to my knowledge.

I would say the video (see the source link) tends to support their claims as it shows small dimples as melting first. Typically molded plastics have pockets of poorly set plastic -- structural weak points. If exposed to a large amount of heat, theses would go first, hence the dimpled look.

Would it help if Toyota applied a glossier finish? Say silver? Sure. But the victim's car (and its mirrors) were black.

At the end of the day, the key problem here IS the windows, if the results are confirmed. After all, do you really want your neighbors melting your kids' sandbox and toy trucks? Are you going to blame Tonka for "poor quality" in that they didn't protect their plastics against an intense solar beam?

And you can be sure that if you have a lawn and/or backyard garden/landscaping, a 120 F beam will do a pretty good job cooking them. Is it the plants fault for not being designed well enough?

The current incident showcases the problem nicely as its the worst case scenario -- a black plastic. This makes it the perfect color to absorb the majority of the visible and near-visible spectrum. Anyone who's run outside on a sunny day in a black T-shirt knows this. Basic physics.

From what I understand there are alternative gloss treatments that reflect a more diffuse, scattered light.

RE: Umm
By tastyratz on 1/26/2012 1:13:10 PM , Rating: 2
Precisely on point
To the original OP... abs plastic has been used to cast a majority of automotive plastics from bumpers to mirrors to window trims or antenna flashing for 20+ years. The same abs plastic mirror having the "issue" is likely no different in composition than cars nearing antique status. This does present a quite unique situation though. Maybe it would be wise in hotter regions to enact ordinances on special reflective treatments that have a scatter pattern (diffusing the light). Otherwise yea, it's like lining your house with mirrors.

RE: Umm
By bupkus on 1/26/2012 2:50:59 PM , Rating: 1
Maybe it would be wise in hotter regions to enact ordinances on special reflective treatments that have a scatter pattern (diffusing the light).
What?! No resentful opines about more government interference? Where's the damning references to liberals, Democrats, socialists, Obama controlling all facets of our lives?... <Inaudible sigh>

RE: Umm
By Reclaimer77 on 1/26/2012 2:53:49 PM , Rating: 1
Are you serious or just trolling?

A state or neighborhood ordinance for something like this is entirely acceptable and, frankly, preferred. States rights, look it up. What in the hell does that have to do with Obama or the "government"?

RE: Umm
By The Raven on 1/30/2012 1:07:51 PM , Rating: 2
You forgot Republicans.

Actually this would preferably be kept between the parties involved and keep even the local gov't out if possible. It should be my right to reflex light wherever I want and for whatever reason if it doesn't hurt anyone else. What if there was a solar panel where the car was? That would be a good reason to do it.

Do we need an ordinance for excessive <insert problem here>? No. You can call the cops to help with your neighbors even if there isn't a law. And if it elevates higher than that we have a court system.

And if that fails, set up a mirror to reflect the same light at their car ;-)

RE: Umm
By mlmiller1 on 1/26/2012 1:22:39 PM , Rating: 2
The open carport receives enough radiant heat to raise the air from 77 to 120 degrees? Peak solar about 1kw per meter sq. So 1KW direct from sun and assume 1kw for reflection. With 120 degree ambient. So at what point does the black body mirror housing obtain convective heat balance with the incident radiation of 2kw/meter? Yep about 200C, good melting point for most PVC's

RE: Umm
By AnnihilatorX on 1/26/2012 5:02:38 PM , Rating: 1
Your figure is way too lax.

The black body mirror cannot have 1kw per sq. meter surface area, that's a huge mirror housing.
More like 250cm^2= 0.025m^2.

Reflection is not 100% efficient either, I'd say 90% since you are assuming a 1sq. meter window project all it's reflection on the mirror with no missed beam.

So the radiation input is 0.925kW

RE: Umm
By mlmiller1 on 1/26/2012 5:53:37 PM , Rating: 2
Yep the 2KW / meter sq. is general, but is the rate that a surface receives heat, regardless of the surface area (assuming no lens or focusing effect). This basically cancels area out of this, "back of the envelope" type "is it possible," calculation. Area cancels because convective heat transfer (cooling) very proportional to surface area, as is heating (the area exposed to the radiation (light)).

To be more accurate looks like 85% of infrared ration is reflected for the below film:
PVC melts from 100-260C

So 1.85KW/meter sq. is still enough to melt some PVC. (1kw from sun, .85 from reflection)

Solar Absorption for black paint is 0.98 (white is like 0.25)

From this we can see that if painted white it wouldn't hit over least on the back of the envelope.

From the pic, looks like the convective currents (at the more vertical parts) get cooled enough. Its just the top has a slower moving air currents and then heats up, then melts.

RE: Umm
By drycrust3 on 1/26/2012 2:14:41 PM , Rating: 2
The interesting thing here is that the damage is outside of the car. There doesn't appear to be any internal damage too, which is what one would expect.
Looking at the video, it appears another car which also uses the same car port also has the same damage; and it also appears the light is focused and not an even spread, which would point to either a manufacturing defect in the window concerned or the way the reflective coating was applied caused the window to become slightly concave.
As a thought, if the thermal expansion and contraction of the reflective coating was significantly different from that of glass, then it could cause the window to focus light under the right conditions. E.g. if the coating was internally applied and the thermal expansion of the coating was greater, then when the window and the coating are warmer than when the coating was originally applied then the reflective coating would actually "suck" on the window causing it to focus sunlight.

RE: Umm
By Iketh on 1/27/2012 12:35:55 AM , Rating: 2
I think interiors are built to withstand a significant amount of heat already.

RE: Umm
By JediJeb on 1/27/2012 3:54:39 PM , Rating: 2
The interesting thing here is that the damage is outside of the car. There doesn't appear to be any internal damage too, which is what one would expect.

I was thinking about this. Conclusion is that glass transmits UV radiation very well but transmits IR radiation poorly. In direct sun your interior heats up because the UV heats the components inside the vehicle which then radiate off IR radiation as heat which does not get transmitted back through the glass and causes the interior temperature of a vehicle to rise far above the outside air temperature. If the coating on the building is reflecting more IR than UV then it is going to heat up the outside of the vehicle more than the inside since the glass on the vehicle will not transmit it.

RE: Umm
By Trisped on 1/26/2012 5:35:17 PM , Rating: 2
I don't believe it is 100% the window. In fact, I would be surprised if the window was at fault at all.

You can tell from the video that the reflected light is rather dispersed by the time it hits the ground, and since the window is not concave the light would not have passed its focal point so the mirror would have received even less light.
There is no other direct light hitting the car because the car port is covered, so the only source of light is from the relatively small window.
The window is transparent, so not all of the suns light is being reflected as some will continue through the glass.
The melting on the other car was at a strange angle compared to the window (which is located on a wall above it). I would have expected the melt to have covered the whole area exposed to the glass, not just a small stretch of it.

While I do agree that the mirror damage looks heat related, the window does not look like the source.

“So far we have not seen a single Android device that does not infringe on our patents." -- Microsoft General Counsel Brad Smith

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