| Author |
Message |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 553
Registered: 08-2004
| | Posted on Thursday, August 07, 2014 - 10:26 pm: |    |
Resurrecting this thread...I was told by a skylight manufacturer that laminated glass cannot be made with 2 lites of tempered glass, but only HS glass. I have read many references to laminated glass using tempered. Any input from anyone one this? |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 554
Registered: 08-2004
| | Posted on Thursday, August 07, 2014 - 10:43 pm: | |
Resurrecting this thread...I was told by a skylight manufacturer that laminated glass cannot be made with 2 lites of tempered glass, but only HS glass. I have read many references to laminated glass using tempered. Any input from anyone one this? |
William C. Pegues, FCSI, CCS
Senior Member
Username: wpegues
Post Number: 916
Registered: 10-2002
| | Posted on Thursday, August 07, 2014 - 11:16 pm: | |
Robin,
Is this a skylight or a canopy? That is, is the space on the inside an interior space that is conditioned, or is it an unconditioned space.
If a conditioned space, lets call it a skylight for terminology. You would be talking about an insulated glass unit where the lite to the exterior would be tempered, but not laminated. the glass lite in the insulating unit that faces the interior would be laminated. The tempered would face any impact but if it broke with enough force that it also caused the inner laminated lite to break the laminated light would act as a 'basket', not release from its glazing and catch and hold the broken tempered lite.
If it is a canopy where it is not an insulating unit, then it is just a single laminated unit with the outer lite being tempered for impact and the underside of the laminated unit being heat strengthened (typically due to size and loading requirements. Technically I guess it could be annealed, but I don't think anyone would want to go there.
In my own specs, I don't actually state whether any glass in the laminated unit (in either skylight or canopy configuration) needs to be heat strengthened or tempered, but state that it needs to comply with performance requirements based on the building conditions for the local jurisdiction for the size of the glass. The outer light of canopy configuration (laminated unit) though is always tempered.
Have never gotten a question or comment on either the skylight or canopy configuration in 37 years.
William
William C. Pegues, FCSI, CCS, SCIP Affiliate
WDG Architecture, Washington, DC | Dallas, TX |
Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP
Senior Member
Username: specman
Post Number: 1251
Registered: 03-2003
| | Posted on Friday, August 08, 2014 - 02:15 am: | |
Laminated glass can be made with tempered glass, but it's not easy. Once laminated, the edges cannot be finished and polished--the edges will be "as is." There's really no need to laminate tempered glass, because laminated annealed or heat-strengthened glass will likely pass the safety glazing standard, depending on lite and interlayer thicknesses.
Ron Geren, FCSI, AIA, CCS, CCCA, SCIP
www.specsandcodes.com |
Brett Scarfino (Unregistered Guest)
Unregistered guest
| | Posted on Friday, August 08, 2014 - 05:40 pm: | |
I highly doubt a tempered-tempered laminated lite is needed for stress considerations if your working with 6mm plies of glass...perhaps for large snow loads. One could quickly determine the need for this makeup using ASTM E1300. Very simple math, pull a few values out of the tables/graphs and multiple together and compare to the project wind/snow loads.
Furthermore, I would caution unnecessarily using tempered material where it is not required for safety or strength due to the potential for spontaneous breakage.
In light of this, I would add an unsanctioned fourth "state" of glass: annealed, heat strengthened, tempered, and heat soak tempered. The later being safer safety glass. |
Randall A Chapple, CSI, CCS, AIA, SE, LEED AP
Senior Member
Username: rachapple
Post Number: 86
Registered: 12-2005
| | Posted on Thursday, August 14, 2014 - 03:46 pm: | |
Another consideration if both lites of the laminated unit are tempered and both lites break, will the unit remain in the frame? |
Mark Gilligan SE,
Senior Member
Username: mark_gilligan
Post Number: 680
Registered: 10-2007
| | Posted on Thursday, August 14, 2014 - 03:50 pm: | |
I believe that the ability of fractured laminated glass to stay in the frame depends on the interlayer and the ability of the frame to clamp onto the glass. |
Bill Coady CSI, CCPR
Senior Member
Username: billcoady
Post Number: 8
Registered: 06-2006
| | Posted on Tuesday, August 19, 2014 - 02:19 pm: | |
Laminated glass can be made from two lites of tempered glass. The optical clarity is not as good as if two lites of annealed were used because of the roll wave distortion inherent in heat treated (heat strengthened or fully tempered) glass. In an insulating glass unit used in a skylight in most installations (there are some exceptions) the inboard lite has to be laminated or a screen has to be in place that will catch the glass if it breaks. Whether that laminated glass is annealed, heat strengthened, or fully tempered depends on may factors including size, thickness, presence of tints or low E coatings, etc. Glass for an exterior canopy will have laminated glass that is commonly tempered for the top lite in the laminated configuration and heat strengthened for the lower/underside lite. The tempered upper surface is a bit tougher and resistant to impact breakage while the heat strengthened lower/underside lite will prevent or minimize sagging if the total laminated lite is broken. If both lites in the laminated configuration were tempered and both broke the lite might sag like a wet blanket and potentially pull out of the glazing pocket and fall out of the opening.
Corrections to my old 2009 post in this thread:
**Heat strengthened glass is 3500 to 7500 psi not 2500 to 7500. Not sure if I was just stupid when I wrote that or had fat fingers.
**"Lehr" is not the name of the guy that invented the annealing lehr process. I had been told that by someone I thought knew what she was talking about but have since learned otherwise. |
Dave Metzger
Senior Member
Username: davemetzger
Post Number: 527
Registered: 07-2001
| | Posted on Tuesday, August 19, 2014 - 02:52 pm: | |
We Lehrn something new every day. |
Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP
Senior Member
Username: specman
Post Number: 1253
Registered: 03-2003
| | Posted on Tuesday, August 19, 2014 - 03:00 pm: | |
Oh, that was pane-ful.
Ron Geren, FCSI, AIA, CCS, CCCA, SCIP
www.specsandcodes.com |
Lynn Javoroski FCSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski
Post Number: 1880
Registered: 07-2002
| | Posted on Tuesday, August 19, 2014 - 03:27 pm: | |
But we are en-lite-ened...and de-lite-d |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 680
Registered: 01-2008
| | Posted on Tuesday, August 19, 2014 - 03:35 pm: | |
Busy eh? |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 681
Registered: 01-2008
| | Posted on Tuesday, August 19, 2014 - 03:52 pm: | |
Are you guys stooping low-e-nough? |
Lynn Javoroski FCSI CCS LEEDŽ AP SCIP Affiliate
Senior Member
Username: lynn_javoroski
Post Number: 1882
Registered: 07-2002
| | Posted on Tuesday, August 19, 2014 - 06:22 pm: | |
Can I just float off into the sunset in my little pink dress with the purple sash before losing my temper? I'll wave as I go! |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 572
Registered: 08-2004
| | Posted on Tuesday, October 14, 2014 - 11:18 am: | |
Bill Coady - would you mind emailing me - robin@spectraspecs.com (or Colin -can you email him and ask if you can forward his contact info). I have a glass issue I could use some input on. |
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