Low-E Glass and Fire Risks

Heat generated from double paned low-e window reflected sunlight has been measured in excess of 200 degrees Fahrenheit (93 celcius). While the use of vinyl siding is not common in Australia, the use of low-e glass is increasing. The generated reflected heat is the same.

See explanation below (remembering that in the northern hemisphere both rise and set positions are displaced towards the north in summer, and towards the south for the winter track. In the southern hemisphere both rise and set positions are displaced towards the south in summer, and towards the north for the winter track.)

 

 

What is the problem, and why is this of concern to the fire service? Simply, energy efficient windows (low-e glass) are designed primarily to deflect heat away from the window. When the pane on the outside buckles slightly, caused by differences in air pressure between the inside and outside environments, the result is a window primed to concentrate and divert sunlight in a manner similar to a magnifying glass. Those firefighters out there who fried bugs as a kid completely understand this concept.

Low-e glass is the glass to be used in the Salta developments, and has probably been used in most new apartment buildings. There is a growing and widely recognised problem with its use in the USA and the UK.

The radiant heat from low-e glass can melt vinyl, has burnt people, and there is a real fire risk in high ambient temperatures. (Proven by a Mass.Fire Dept Investigative Unit report).

“Energy efficient Low-e windows work by reflecting a greater percentage of sunlight, especially in the infrared “heat” wavelengths. Insulating glass units are made of two or more panes of glass that are hermetically sealed at the edge, trapping an insulating layer of air or other gas in between. When the pressure between the panes of glass is different from the atmospheric pressure, the glass is designed to bend slightly. When the glass deflects inward, this creates a concave reflective surface that concentrates the reflected beam of sunlight. Objects in the path of the beam may be subjected to temperatures well in excess of those from normal exposure to the sun.” source: VSI Report 2010

Solar radiation that reflects off e-glass is represented by reflectance (the ratio of reflected radiant energy to incident radiant energy). The total solar reflectance of clear glass is typically around 13% of the incident solar radiation. Some low-e glass can reach reflectance greater than 50%…Any concavity will concentrate refleced solar energy at a corresponding focal length. source: University of California, Berkely National Laboratory, report on Glass Solar Reflectance and Vinyl Siding.

“Glass in double paned windows may on occasion slightly warp or deflect due to a difference in barometric pressure between the interior of the glass panes and the outside air pressure. This can create a concavity in the glass. Such a concavity is a normal response to pressure differences, does not affect the performance of the window, and does not constitute a defective window condition. However, the concavity may focus sunlight reflected from the window in a fashion similar to the effect seen when light passes through a magnifying glass. The heat generated by the focused reflected sunlight has proven sufficient to visibly damage and distort vinyl siding on nearby houses. Any double paned window may cause this effect, but double paned low-e windows have a higher reflectivity quotient which can exacerbate the reflected light/vinyl distortion phenomenon.

Heat generated from double paned low-e window reflected sunlight has been measured in excess of 200 degrees Fahrenheit (93 celcius),  more than sufficient to soften and distort any normal grade or color of vinyl siding. There have been some reports of reflected sunlight damage to materials other than vinyl siding. Occasional wood discoloration and charring, and damage to paint and other plastics (e.g.,decking, window lineals, trim), have all been reported.”

source: Lieutenant John Shafer, 18 year veteran of the fire service, and currently the Training Officer for the Greencastle Fire Department, and an Indiana regionally recognized instructor on building construction, fireground search and command management who delivers specialized training programs on building construction, fireground search and firefighter safety.

 

Several articles are available from Fire Chief Kevin Gallagher from Massachusetts:

“Back in October 2013, I wrote an article for this column on the very real phenomenon of sunlight reflecting off energy efficient windows and causing damage to vinyl siding. As that article noted, the nationwide push for greater energy efficiency has resulted in the adoption of stricter energy codes. Reducing our carbon footprint is the goal, but sometimes this can result in unexpected consequences.

What is the problem, and why is this of concern to the fire service? Simply, energy efficient windows are designed primarily to deflect heat away from the window. When the pane on the outside buckles slightly, caused by differences in air pressure between the inside and outside environments, the result is a window primed to concentrate and divert sunlight in a manner similar to a magnifying glass. Those firefighters out there who fried bugs as a kid completely understand this concept.

The October 2013 article discussed several examples of vinyl siding becoming distorted in some cases and melted in others. The amount of heat reflected off these windows is—in some cases—great enough to cause damage from considerable distances.

Captain Ed Collins of the MFD Investigative Unit, and Captain John White produced an investigative report that gives evidence of a structure fire caused by reflected sunlight.

In part, it states: “sunlight reflecting off of one energy-efficient window generates enough concentrated heat energy to burn a dried-out area of lawn. The occupant will not see smoke or fire but notes the smell of burning brush during the day. Smoldering continues during the next 15 hours until it reaches shrubs. Enough heat energy is present to ignite the shrubs with the subsequent fire extending to the exterior of the house. Extension to the interior stopped by civilian extinguishment actions. (The MFD fire report states that, while battery smoke detectors were present, they would have failed to work because of the batteries having been removed.)”

source: Kevin A. Gallagher has served with the Acushnet (MA) Fire & EMS Department since 1986, where he was appointed as chief in 2003. Gallagher has an associate degree in fire science and a bachelor’s degree in political science. He is an adjunct instructor in the Fire Science Program at Bristol Community College. Gallagher serves as the Fire Chiefs Association of Massachusetts representative to the Board of Building Regulations and Standards, the Massachusetts board responsible for overseeing the state’s building code. He has contributed articles to Fire Engineering and has taught several classes at FDIC on the issue of modular construction.

The real problems with the low-e glass to be used are that as well as the possibility of the large expanses of low-e glass starting fires on the opposite bank, and making it a much more unpleasant environment for recreational users because the radiant heat will effectively make the entire river corridor hotter, this is going to cause huge problems for animals, birds and reptiles.

The building also uses aluminium on its surfaces. Aluminium reflects 90% of sunlight, causing excessive glare and reflected heat.

Some other links/souces :

“The Effect of Reflected Sunlight from Low-e and Other Double Paned Window Glass on Vinyl Siding,” prepared by the National Association of Home Builders (NAHB, February 2010).

The Vinyl Siding Institute (VIS) issued an advisory on solar reflection and heat distortion in July 2010.

In 2010 the Board of Building Regulations and Standards, the state board that promulgates the Massachusetts State Building code, issued an advisory stating in part that, “Under certain circumstances, vinyl siding, in the presence of window reflected sunlight, can distort, and in some instances significantly distort.”

2011 University of California (Berkely National Laboratory) report titled Research Needs: Glass Solar Reflectance and Vinyl Siding,    authors: R.Hart, C.Curcija, D.Arasteh,H.Goudey,C.Kohler, S.Selkowitz.

2014 US television report: http://www.wral.com/glare-from-energy-efficient-windows-can-melt-siding-vehicles/13614716/

2015 London Fire Brigade Report: http://www.london-fire.gov.uk/news/LatestNewsReleases_warningassunstunscelebrity.asp

2013 UK news article: http://news.nationalpost.com/news/london-skyscrapers-deathray-reflection-is-melting-cars-burning-businesses-but-also-cooking-eggs

2013 BBC News ‘Walkie-Talkie’ skyscraper melts Jaguar car parts

http://www.bbc.com/news/uk-england-london-23930675

 

 

We would like to thank local residents and concerned river users for these contributions. If you have more environmental information about the area, please contact us. We will publish your information, with attribution, or you may remain anonymous if you wish.

Residents and river users have valuable insights and information to share and these deserve to be heard by our politicians and the wider community.

 

 

 

 

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