My pool is burning

[merc123]

It's not clear to me why this is happening. It doesn't seem like the reflection from a flat pane of glass would magnify the sun. Is it because the area being affected is receiving sun directly and from the reflection, in effect getting almost "two full doses?" Does it only happen when the affected area gets both, or can something melt from just the reflection that wouldn't ordinarily melt from just being in the direct sun?

It's the low-e. This article explains it better than me. Also it's winter time here so the angle of the sun is different than summer causing it to be more reflective toward the ground. It does a magnifying glass type effect.

Reflections of a Product Defect - Safety Research & Strategies, Inc.

Some homeowners try to reduce their maintenance time and costs by cladding their homes with vinyl. Others try to reduce their heating and cooling bills by installing energy efficient low-e windows. And if one of these types of homeowners lives close enough to the other, and the angle of the sun...

www.safetyresearch.net

 

[JoyfulNoise]

It's not clear to me why this is happening. It doesn't seem like the reflection from a flat pane of glass would magnify the sun. Is it because the area being affected is receiving sun directly and from the reflection, in effect getting almost "two full doses?" Does it only happen when the affected area gets both, or can something melt from just the reflection that wouldn't ordinarily melt from just being in the direct sun?

No glass pane is truly flat, especially a large pane like that. Even minor curvatures over a long enough distance will act like a magnifying glass. The coating reflects the infrared part of the light spectrum only. That is where most of the sun’s energy output is. It is also the wavelength(s) of light that cause direct heating. Normally IR light would be diffuse and randomly reflected (specular reflection), but the glass is “selecting” the hottest portions of the sunlight and directing it onto a surface. That will easily cause heating and melting even if the glass were perfectly flat.

 

[merc123]

Wow... you guys have already mentioned all the ideas I had with the exception of one.. grow a hedge. They look nice, add privacy and block the sun too.

Unfortunately we aren't able to grow a hedge in a location that would block it from the window.

 

[JamesW]

The window is concave due to a difference in the pressure between the interior of the glass panes and the outside air pressure. This effect is more pronounced in the cooler months, as the gases between the panes of glass contract and pull the outer pane in.

A report of fire damage in January 2015 on the north exterior wall of a home in Whitman, Mass. The state Fire Marshall determined that the mostly likely cause was the concentrated reflection of sunlight coming from an adjacent home’s second floor windows. The building’s homeowners told fire officials that it was the second time the vinyl siding on that side of the house had been melted and replaced.

In November 2016, a neighbor’s low-e window burned a four-foot square patch of mulch, in Waxhaw, North Carolina.

On January 28, 2017, the state Forest Service extinguished a fire at an Advance, North Carolina residence that destroyed an old dog house and burned a patch of ground covered in pine straw. Four days later, the department responded to another fire in the same area and determined that it was set by the reflection of sunlight off the neighbor’s second-story window. Fire investigators measured the temperature at the cross-shaped reflection at 341 ºF.

On January 6, 2018, low-e windows were blamed for burning through the wooden shingles of an adjacent house in Somerville, Mass. through to the framing underneath. It was the second incident in six years.

In Las Vegas, the Vdara Hotel’s 57-story structure with a curved exterior threw a concentrated beam of heat, burning hotel guests arrayed around the swimming pool area below, causing one news outlet to dub it a “death ray.”

 

[Homebrewale]

Wow... you guys have already mentioned all the ideas I had with the exception of one.. grow a hedge. They look nice, add privacy and block the sun too.

You'll now have a burning hedge instead of a burning pool.

 

[Dirk]

It's the low-e. This article explains it better than me. Also it's winter time here so the angle of the sun is different than summer causing it to be more reflective toward the ground. It does a magnifying glass type effect.

Reflections of a Product Defect - Safety Research & Strategies, Inc.

Some homeowners try to reduce their maintenance time and costs by cladding their homes with vinyl. Others try to reduce their heating and cooling bills by installing energy efficient low-e windows. And if one of these types of homeowners lives close enough to the other, and the angle of the sun...

www.safetyresearch.net

Got my answer, thanks guys. The angle of the sun plays a part, in the aiming. The panes are not reflecting all of the sun's energy, as you'd expect, but temperature differentials between the outside air, inside air, and especially between the panes of the dual- or triple-pane windows are pulling at the glass and curving it, which explains how the now focused rays exceed the normal rays. So it's not a factor of both the reflected energy and the direct rays hitting something, it could happen from just the reflection. Crazy.

Interesting how this phenomenon made it out into the wild without any manufacturer being aware of the possibility...

 

[Newdude]

So if I am reading the pics right, how about a hedge between the pool and the house. That way it will block the sun from reflecting on the pool

I can attest to this solving one problem and creating another. That same laser beam reflection will burn the hedge instead. It took me 7 years to realize that my pool was reflecting and killing whatever I planted on the back side. The only thing that would last was Hostas which I initially chaulked up to them being the dandelions of plants that can live anywhere. Anything else would take root and be good for a year but once they were 18 inches tall they would fry in the sun reflection off the pool. The front and sides of the pool had no problems growing anything. The shorter Hostas never grew tall enough to get burned on the backside. In this instance the hedge would be between A and B so it would take the brunt from day 1.

 

[Dirk]

All that makes me think just putting a sticky film on the glass might not solve the problem, as the curve would still be there.

I offered up the idea of the louvered storm shudder, which could work. Which I now regret: because ever since I googled "storm shudders" to come up with the image I posted, every webpage I now visit has an ad for storm shudders!! Talk about strange forces!

 

[markayash]

I

 

[mgtfp]

Reflect that heat to my pool

Just don't forget to remove the pool cover first. I read somewhere that that could burn a hole in your cover

 

[mguzzy]

You'll now have a burning hedge instead of a burning pool.

Well, I was thinking the hedge would be positioned to block the light that would be incident on the window.. not after it got reflected from the window.. but ok!. Then put in a solar collector there and use all that energy to charge your Tesla or something

 

[red-beard]

No glass pane is truly flat, especially a large pane like that. Even minor curvatures over a long enough distance will act like a magnifying glass. The coating reflects the infrared part of the light spectrum only. That is where most of the sun’s energy output is. It is also the wavelength(s) of light that cause direct heating. Normally IR light would be diffuse and randomly reflected (specular reflection), but the glass is “selecting” the hottest portions of the sunlight and directing it onto a surface. That will easily cause heating and melting even if the glass were perfectly flat.

Some "Low-E" are also "Low UV". They also reflect UV light, which can help reduce the chance wood and other interior products are not faded by UV. According to this article, it is the same coating, just thicker for UV protection.

Low-E Glass vs. Low-E UV Glass: What’s the Difference? - Omaha Door & Window

 

[JoyfulNoise]

Some "Low-E" are also "Low UV". They also reflect UV light, which can help reduce the chance wood and other interior products are not faded by UV. According to this article, it is the same coating, just thicker for UV protection.

Low-E Glass vs. Low-E UV Glass: What’s the Difference? - Omaha Door & Window

Probably not worth the additional cost to most homeowners. UV-B and UV-C radiation are completely absorbed by standard soda-lime glass that windows are made of. SL glass can transmit up to 70% of UV-A that hits it depending on additives used in the glass. There’s not a lot of energy in the solar UV part of the spectrum so heating from UV is insignificant (it mostly causes chemical reactions to occur because the UV photons directly excite electron transitions in atoms and molecules). So it’s probably cheaper to just treat your wood furniture with a good wood polish and frame pictures in UV blocking glass frames then spend the extra money on thicker glass coatings which I’m sure they charge a lot for ...

 

[red-beard]

Can Reflective Buildings That Produce 'Death Rays' Be Prevented?
A recent car-melting incident in London is not the first time a building has produced high-temperature beams.


Imagine parking your car downtown for an hour and coming back to find parts of it melted. That's what happened to London motorist Martin Lindsay, who told the BBC that the wing mirror and badge portions of his Jaguar had melted due to intense sun rays reflecting off the Walkie Talkie tower. The 37-story skyscraper, due for completion in 2014, has a mildly curved facade, which results in a convergence of sunlight and extremely strong beams.



The building's developers, Land Securities Group PLC and Canary Wharf Group PLC, were quick to respond, releasing a statement blaming the car-melting rays on a particular elevation of the sun in the sky that day. Based on preliminary computer modeling, they say the phenomenon happens two hours per day and expect it to go on for two or three more weeks.



The developers have already paid for the Jaguar's repairs and have blocked three parking spaces near the building. They're now working with the city of London to find solutions. According to the BBC, some possibilities may be applying a finish to the glass to reduce reflection or realigning the window frames slightly.



Can Reflective Buildings That Produce 'Death Rays' Be Prevented? - Bloomberg

 

[JamesW]

The architect responsible for the Vdara hotel, Rafael Viñoly, is, not coincidentally, the same architect behind London's Walkie Talkie tower.

So, apparently, the architect likes creating "Death-Ray" buildings.

The building's design is responsible for the problems in the above referenced buildings whereas the flat glass panes are concave due to low pressure between the panes of glass in double or triple pane windows.

So, two different causes of similar problems.

 

[superuser]

In my last house I lost all my patio furniture cushions over time due to the same effect. A wall of Low E3 glass and a west facing patio meant smoking cusions

 

[merc123]

All that makes me think just putting a sticky film on the glass might not solve the problem, as the curve would still be there.

I offered up the idea of the louvered storm shudder, which could work. Which I now regret: because ever since I googled "storm shudders" to come up with the image I posted, every webpage I now visit has an ad for storm shudders!! Talk about strange forces!

If you place it on the exterior of the glass it will, just like a louvered shutter.

 

[Dirk]

Sounds good. Have you done it yet? Keep us posted...

 

[merc123]

Going up today. So far it seems beneficial. However one problem solved with another arising. The window to the right is also doing it, albeit with a lot less intensity. The screen may disperse some of the heat. I’m surprised it hasn’t melted.
You can stand in front of that with the beam on your head. It feels warm but not burning. I have left over I may cover that one as well.

 

[Newdude]

The screen may disperse some of the heat

That’s a GREAT idea !!! What about actual screens ? It would scatter the ray of sunshine before it hits the window and scatter it even more on the way back out, hopefully making it less laser-y and more shotgun of sunshine.

you would probably only need them for a few weeks now and in 6 months when the sun hits that magical angle again.