To Temper or Not to Temper – that is the question
idahobuild
| Posted in General Questions on
Hey all,
We’re preparing to order our windows and need some feedback on interpreting the “Glass and Glazing” section of the 2018 IBC (atch’d). The window manufacturer/sales rep has made recommendations, but has admitted to having issues. My local inspector isn’t returning my call.
Great Room Window Sill – 19″ above floor
Master Shower Window Sill – 5′ 6″ above floor
Master Tub Window Sill – 4’3″ above floor
All 3040 Window Sills – 2′ 9″ above floor
Where do we need safety/tempered glass?
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Replies
Can you make your question and your supporting info a little more clear? I'm up in Canada, so our code language is a little different. But I read the attached IBC screenshot and I'm not sure why you're asking about tempered glass.
Tempered glass is a process iny the manufacturing to which the end result is it makes it stronger in general but if you break the glass it breaks into tiny particles instead of very sharp shards. This is safer I'm the sense that you don't get major cuts or any sever any major arteries. It doesn't stop you from falling through the glass, say from a 3rd storey.
When you say safety glass, and give a bunch of measurements to the bottom of sills, I think you are referring to laminated glass, to which it'll stop you from fallening through the glass.
Moreover, in my land of code, non-laminated glass is ok to be used when the sill is under 36", however you have to limit the operation of the window range of motion to prevent any accidental falling. Window manufacturers have a metal string mechanism that they can provide to meet this. Basically the window only opens a crack. Unless you use a double action to disable it.
I hope this helps.
Deleted
jberks,
From what I can see in the BC building code, laminated and tempered are both approved as safety glass where it is required.
Malcolm,
I had this conversation recently with a rep for a high-end European window brand. He confirmed that both laminated and tempered could work as safety glass.
I don't recall all the ins and outs of why he recommended tempered instead of laminated in our case (triple pane steel windows), but he did caution that there was a slight, if barely perceptible, difference in how light moved through and reflected off of laminated or tempered compared to non-safety glass. For that reason, we went with laminated throughout the house, so all the window glass would look the same.
Might be something to consider, idahobuild - unfortunately, I don't have the numbers to know what going all-tempered added to the order's cost.
In the IRC model codes that most of the US uses for its local codes, glazing in "hazardous locations" must be "safety glass." It could be laminated safety glass but in almost all situations it's tempered glass so as a rule we just say "tempered."
The code language is precise yet confusing: https://codes.iccsafe.org/content/IRC2018/chapter-3-building-planning#IRC2018_Pt03_Ch03_SecR308.4.
Here's my take, though as always it's the AHJ's opinion that matters:
Great Room Window:
Doesn't meet ALL the criteria for "hazardous location," R308.4.3 IRC / 2406.4.3 IBC Glazing in Windows
So, you should be good here without safety glazing.
Master Shower Window:
Looks to me like the window is not actually in the shower? It's a bit hard to tell from the plan screenshot. It's adjacent to and within 60" horizontally of the shower, but the bottom of glazing is 66" above the floor, so according to R308.4.5 IRC / 2406.4.5 IBC Glazing & Wet Surfaces, it's NOT considered to be in a wet location, so also not a hazardous location, so does NOT require safety glazing.
I can't tell if you have a door on that shower, but if you do, then that window is within 24" of the door (IBC 2406.4.2), however the code says that to require safety glazing the window must be within 24" of a door AND have the bottom edge of glass less than 60" above the floor. So because you don't meet both criteria, you should be okay.
Master Tub Window:
Unlike above for the master shower, must be safety glazing because it's adjacent to a wet location, AND the bottom of glass is less than 60" above the floor. So, safety glazing required here (for every pane of the window).
You have some options for "safety glazing," namely laminated glass or tempered glass. If I'm incorrect there, someone please jump in. Oberon recently wrote a great Part One article about laminated glass:
https://www.greenbuildingadvisor.com/article/laminated-glass-part-1
Well worth a look:
https://www.greenbuildingadvisor.com/article/what-to-know-about-tempered-glass
https://www.greenbuildingadvisor.com/article/laminated-glass-part-1
"Where do we need safety/tempered glass?"
Great Room Window Sill – 19″ above floor
>Not required if glazing itself (not the wood sill or window frame) is 18" or more above the finished floor. Some manufacturers will automatically make larger glass panes tempered anyway, though.
Master Shower Window Sill – 5′ 6″ above floor
>Not required where the bottom edge of the glazing is 60" or more above the floor. So not required here.
Master Tub Window Sill – 4’3″ above floor
>Required
All 3040 Window Sills – 2′ 9″ above floor
>If that's what is in your guest bath, it would be required there.
Otherwise I don't see anyplace else it should be required. But in my experience, AHJs don't always understand the fine points as well as they could.
I think we have the Master and Guest bathroom as well as Great Room sorted out.
What about the two windows closest to the front door? Both are 3040 and sill is 2'9" above floor. There are interior walls between each of those wondows and the door.
Then the kitchen window (near the back door)
Which is 42 " above floor (about 6" above sink). The back door is within 2 feet of some of the pains.
Do these windows need to be tempered?
I don't see any windows near the front door. R308.4.2 exception 2 says that if there is a wall between a door and a window, it's not a hazardous location. So that clears the back door as well.
You're always free to make as many windows tempered as you want, if you're concerned about safety.
I used to be concerned with the difference in how light comes through regular glass vs. tempered glass, but resident window expert Oberon/Greg Novak has convinced me that it's only an issue if you're wearing polarized lenses indoors, which would be pretty unusual.
Michael - It seems like I breezed over the "...windows near the front door" part of your response. There is one on either side of the front door. Both are just under 5 feet away (image atch'd). But there are interior walls between each and the front door -- that is why I was asking about whether the walls being 'interior' made a difference.
Thanks Michael - so the walls between the door and windows is interior not exterior - correct?
Where tempered is not required, I can consider the cost savings there and use the funds in other locations where not required, but close. For example, the Great Room window sills are pretty low and if we ever have little ones around we might want thosee tempered.
Either way, there are walls between the door and the glass. As I understand it, the reason for tempering glass within 24" of a door is mainly so that if the door is slammed shut, it won't break the adjacent glass. Any wall will dampen the vibrations enough that it shouldn't be a problem.
Some or most window manufacturers temper larger panes of glass anyway, because the extra strength helps during manufacturing and shipping, and probably in part for liability reasons after installation. If you're worried about kids getting hurt, tempering is pretty affordable insurance.
I dont know where your structure is being built but there is also the issue of Wildland urban interface which requires all glazing to be tempered for fire resistance. It may be worth it even if you are just worried about it and it is not required.
freyr_design,
Glad to see you posting again. You add a lot to the discussions.
Ya, busy outdoor summer, just getting back to computer work. Thanks for the comment.