>On Sun, 07 Nov 2010 00:09:05 -0400, clare@snyder.on.ca wrote:
>>On Sat, 6 Nov 2010 17:27:23 -0700, "ghelf"
>>
>>>So are you saying the window film broke the glass; that the film shrinking
>>>and expanding put too much pressure on the glass?
>> No, the rejected heat from the film mounted on the inner glass
>>cracked the outer glass. There was likely a minor stress/chip at the
>>edge of the glass that broke - which may have caused the glass to
>>greak in the next couple of years - but the glass had lasted about 2
>>years without the film, and only a matter of hours after the film was
>>installed.
>>
>>Apparently NOT an un-common occurrence.
>Snipped from link below:
>Will Window Films Cause Glass To Break?
>Glass breaks when stressed. There are five types of stress which may
>cause glass breakage:
>1. Thermal Stress--from absorption of solar radiation.
>2. Tensile Stress--from the weight of the glass itself.
>3. Mechanical Flexing Stress--from wind.
>4. Impact Stress--from flying objects, hail, baseballs.
>5. Twisting Stress--from building or window frame sagging or
>settling.
>The first type, thermal stress, is the only one which film may affect.
>The use of window films will increase the thermal stress on sunlit
>glass. However, there are also other factors which will increase
>thermal stress such as: partial shading of windows from overhangs,
>tightly fitting drapes or blinds, signs or decals on windows, heating
>and cooling vents directed at glass. In addition, different types of
>glass (annealed versus tempered, clear versus tinted) have different
>solar absorption rates and will withstand different degrees of thermal
>stress.
>The window film manufacturers have recommended film-to-glass tables
>for use by factory-trained dealer installers. If a consumer is ever in
>doubt, he/she should request a copy of such guidelines. Listed are
>some glass types or conditions where the use of a solar control (not
>clear safety) type of window film is not recommended without extreme
>caution.
>SINGLE PANE GLASS LARGER THAN 100 SQUARE FEET.
>DOUBLE PANE GLASS LARGER THAN 40 SQUARE FEET.
>CLEAR GLASS THICKER THAN 3/8 INCH.
>TINTED GLASS THICKER THAN 1/4 INCH.
>WINDOW FRAMING SYSTEMS OF CONCRETE, SOLID ALUMINUM, OR SOLID STEEL .
>GLASS WHERE SEALANT OR GLAZING COMPOUND HAS HARDENED.
>VISIBLY CHIPPED, CRACKED OR OTHERWISE DAMAGED GLASS.
>REFLECTIVE, WIRED, TEXTURED, OR PATTERNED GLASS.
>TRIPLE PANE GLASS.
>LAMINATED GLASS WINDOWS
>http://www.iwfa.com/iwfa/Consumer_Info/qa.html
These windows were pushing the 40 sq ft limit - but some slightly
larger windows didn't break, while some of the slightly smaller ones
did.
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>>On Sat, 6 Nov 2010 17:27:23 -0700, "ghelf"
>>
>>>So are you saying the window film broke the glass; that the film shrinking
>>>and expanding put too much pressure on the glass?
>> No, the rejected heat from the film mounted on the inner glass
>>cracked the outer glass. There was likely a minor stress/chip at the
>>edge of the glass that broke - which may have caused the glass to
>>greak in the next couple of years - but the glass had lasted about 2
>>years without the film, and only a matter of hours after the film was
>>installed.
>>
>>Apparently NOT an un-common occurrence.
>Snipped from link below:
>Will Window Films Cause Glass To Break?
>Glass breaks when stressed. There are five types of stress which may
>cause glass breakage:
>1. Thermal Stress--from absorption of solar radiation.
>2. Tensile Stress--from the weight of the glass itself.
>3. Mechanical Flexing Stress--from wind.
>4. Impact Stress--from flying objects, hail, baseballs.
>5. Twisting Stress--from building or window frame sagging or
>settling.
>The first type, thermal stress, is the only one which film may affect.
>The use of window films will increase the thermal stress on sunlit
>glass. However, there are also other factors which will increase
>thermal stress such as: partial shading of windows from overhangs,
>tightly fitting drapes or blinds, signs or decals on windows, heating
>and cooling vents directed at glass. In addition, different types of
>glass (annealed versus tempered, clear versus tinted) have different
>solar absorption rates and will withstand different degrees of thermal
>stress.
>The window film manufacturers have recommended film-to-glass tables
>for use by factory-trained dealer installers. If a consumer is ever in
>doubt, he/she should request a copy of such guidelines. Listed are
>some glass types or conditions where the use of a solar control (not
>clear safety) type of window film is not recommended without extreme
>caution.
>SINGLE PANE GLASS LARGER THAN 100 SQUARE FEET.
>DOUBLE PANE GLASS LARGER THAN 40 SQUARE FEET.
>CLEAR GLASS THICKER THAN 3/8 INCH.
>TINTED GLASS THICKER THAN 1/4 INCH.
>WINDOW FRAMING SYSTEMS OF CONCRETE, SOLID ALUMINUM, OR SOLID STEEL .
>GLASS WHERE SEALANT OR GLAZING COMPOUND HAS HARDENED.
>VISIBLY CHIPPED, CRACKED OR OTHERWISE DAMAGED GLASS.
>REFLECTIVE, WIRED, TEXTURED, OR PATTERNED GLASS.
>TRIPLE PANE GLASS.
>LAMINATED GLASS WINDOWS
>http://www.iwfa.com/iwfa/Consumer_Info/qa.html