| Author |
Message |
Brett Wilbur
Member
Username: brett_wilbur
Post Number: 3
Registered: 09-2022
| | Posted on Thursday, September 29, 2022 - 05:16 pm: |    |
Late to the party again. Lots of great conversation here in 2016 to 2020, and the previous post in 2006. Correct me if I'm wrong but heat-soak requirements were only added to MasterSpec in Q2 2019 even though it appears to have been around in the industry a lot longer. I'm curious, barely any mention of warranties for heat-soaking in these threads, which was also added to MasterSpec at the same time.
We have a fabricator(design-build glazer) that is balking at the warranty for heat-soaked glass. I see several glass manufacturer's, Viracon and OldCastle, that will provide the warranty, so we are not sure what their issue is yet. In fact, the language added to MasterSpec is the exact language in Viracon's heat-soak warranty. They are also unwilling to run a thermal stress analysis even though the contract is delegated design / design-build.
There is also a requirement in MasterSpec for a manufacturer's certificate stating that their "products meet the specified glass breakage probability requirements for indicated applied loads, that expected thermal stressing of products is acceptable and that glazing details (if required by glass fabrication manufacturer) have been reviewed and are approved." This seems to have more meat than the warranty but not sure beyond certification if it can be held against them in court. It also says that thermal analysis is requried. The contractor is saying the Architect should do that in design.
I'm also curious how they forensically determine glass brakeage due to enlarged NiS inclusions due to thermal stress on the glass. If the certification covers thermal stresses, shouldn't it cover breakage due to inclusions since thermal stress causes the inclusions to break the glass? There are other ways the glass could fail, but I know of no other way the inclusions could break the glass without thermal stress being the cause. I welcome any new thoughts, especially on the heat-soak warranty for glass required to be heat-soaked. |
William C. Pegues
Senior Member
Username: wpegues
Post Number: 993
Registered: 10-2002
| | Posted on Thursday, September 29, 2022 - 05:33 pm: | |
Brett,
Late is always better than never!
Spontaneous breakage can be caused by crystals that grow in the glass. Heat may start the process, but it does not have to be present for it to happen. It is typically in tempered glass that this happens since tempered glass has a surface tension aspect to it.
But, its very rare. In 40 years of doing more than 400 projects in various parts of the country, none of my projects ever had a problem. But I have seen it happen personally twice. Once was on a project that due to exposure had tempered glass on the exterior light of an insulating unit. After a few years, some of the exterior panels started to spontaneously break. A glass professional easily identified the crystals, and with his magnifying loop you could see the crystals easily.
The other location was personally experienced by my wife. She was outside an exterior office at work when there was a ‘bam’ from an the office (unoccupied at the time) and looking inside a huge slab of glass was cracked. You could see the starting locations. This too was inspected by the building owner and a glass specialist and photos easily revealed the crystal.
As I noted several year ago in the earlier part of this thread, I have never specified the heat soaking process UNLESS this is structural glass glazing - where the glass is a structural element. You don’t want that to break then.
On other projects when this topic came up, the glass manufacturer always offered an addition to the warranty to cover any breakage due to crystal inclusions in the glass.
William C. Pegues, FCSI, CCS, SCIP |
Dan Helphrey
Senior Member
Username: dbhelphrey
Post Number: 115
Registered: 12-2018
| | Posted on Thursday, September 29, 2022 - 06:07 pm: | |
"Spontaneous breakage can be caused by crystals that grow in the glass. Heat may start the process, but it does not have to be present for it to happen. It is typically in tempered glass that this happens since tempered glass has a surface tension aspect to it."
Currently replacing the infill of several (formerly) glass guardrails with steel pickets over this issue - it only happened a couple times, but the client has decided to replace all the glass guardrails they own due to potential liability. |
William C. Pegues
Senior Member
Username: wpegues
Post Number: 994
Registered: 10-2002
| | Posted on Thursday, September 29, 2022 - 10:08 pm: | |
Dan,
Yes, handrails do seem to be more of a problem. I think because many get their tempered glass from a source other than a major glass fabricator. The crystals come from a contamination in the furnace making the original sheet of glass. I have no evidence of that specifically, just that I seem (over time) to hear about handrail problems more than window glass.
William C. Pegues, FCSI, CCS, SCIP |
ken hercenberg
Senior Member
Username: khercenberg
Post Number: 1519
Registered: 12-2006
| | Posted on Friday, September 30, 2022 - 07:49 am: | |
From a recent discussion with Kuraray, Code now requires the use of structural interlayers at glass guardrails. Tempered laminated is what most railing manufacturers seem to default to. While that allows either structural PVB or ionoplast, I only use ionoplast (SentryGlas) interlayers at railings at this point since structural PVB sags when the glass breaks, potentially allowing a person to fall.
Like William I typically only advocate heat soaking when using structural glazing at fenestrations though we do have clients that request it. |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 832
Registered: 08-2004
| | Posted on Friday, September 30, 2022 - 11:43 am: | |
Ken: Which code version? So, 1/2 inch tempered is no longer acceptable for railings? |
Brian Payne
Senior Member
Username: brian_payne
Post Number: 283
Registered: 01-2014
| | Posted on Friday, September 30, 2022 - 04:54 pm: | |
Since 2015 IBC. Glass infill can use 1/2” temp, but laminate required for structural glass railings where the glass is the guard. |
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