I have a full size double-pane all-glass patio door that I'd like to put a hole in for an air conditioner exhaust hose. I plan to drill a hole with a glass drill bit and then use a carbide rod saw to saw out the 5" diameter hole. I realize this will be a pain in the butt but there are no other places in the apartment I can cut the hole.

How likely is this door (or one like it) to be made of tempered glass? It looks to be at least 10 years old. Not sure how common tempered glass is in these kinds of applications. The apartment isn't really well-built.

The glass is SGG Climalit. I can't find one shred of contact info on their web site to ask them, though it looks like they do offer tempered glass options. This is in Spain. https://www.climalit.es/

Glass logo Better view of door pane construction View of entire door

  • 5
    Even if it's not tempered, do you realize that it is a double-pane insulating window and cutting a hole in it will allow normal air in and defeat its purpose? It'll also get dirt and condensation inside which you'll never be able to clean.
    – brhans
    Jul 4 '18 at 14:30
  • 2
    Large sheets of window glass are (almost?) always tempered, especially when used as a door. Jul 4 '18 at 14:51
  • 2
    Yeah, don't cut a hole in your door. It's just a bad idea for several reasons. It is probably tempered.
    – isherwood
    Jul 4 '18 at 14:59
  • 2
    1) You'll have moisture and dust inside the glass unit, making your door look perpetually filthy, and 2) it's probably tempered (being a door), and will explode when you try to cut it.
    – isherwood
    Jul 4 '18 at 16:00
  • 2
    Yes it is tempered. Don’t drill a hole in it, it will explode the minute you manage to nick the surface. And I don’t believe you - there has to be another place to put a hole to the outside.
    – paul
    Jul 4 '18 at 22:07

Since you clearly are not interested in advise on how to accomplish your task and you only want to know if your glass door is tempered or not AND since we can not answer this question for you then here is a test you can perform.

Step 1, - Cut a hole in the glass of your door.

Step 2, - After the glass breaks, look at the size of the pieces. If it shatters into a million little pieces it is tempered. If it breaks into larger jagged pieces and shards it is not tempered.

You can avoid steps 1 and 2 if you like and proceed directly to step 3 but this will result in you not knowing if your glass is tempered or not

Step 3, - Buy a new door with a half-length window and cut a hole in the non window section.

(This test is for entertainment proposes only, mostly mine although I am sure those who have been tersely rebuked by you for offering advice will probably get a kick out it. IF you do perform this test then I am not responsible for you breaking your glass, cutting yourself or feeling embarrassed for not taking advice offered.)


I would say it is 100% tempered glass if built to code, both the glass in the door and any next to the door are required to be tempered (I don't remember the distance from the door before non tempered is ok) . Added some code references: found a reference from the international building code, 2015 date, 2406.4.1 and 2406.4.2 swinging, sliding and bifold doors require safety glass, if I read it right glass within 24" of a door. Tried to copy and paste but could not do it on my phone , earlier in the article it did specify the type of marking and things like wire embedded , plastic layers like windshields or tempered are all acceptable.

  • There's nothing code about this apartment. But be that as it may, do you have any suggestion on how to find out if this is tempered?
    – Maddix
    Jul 4 '18 at 15:25
  • +1 For @JimStewart , Yes, it will shatter when you start drilling a hole if it’s tempered. In the U.S., there is a small engraved icon or numbers in the corner of the glass.
    – Lee Sam
    Jul 4 '18 at 16:40
  • @JimStewart As I mentioned, this is in Spain, not the US. I also included the engraving in the photos.
    – Maddix
    Jul 4 '18 at 17:09

Get a pair of polarized sunglasses and look at the window (as well as a car rear window for reference)

The strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses.

If it is tempered, you will see a pattern like this:

  • 1
    I believe that will only tell you whether or not it is polarized glass or not but i am not sure.
    – Alaska Man
    Jul 4 '18 at 19:19
  • I agree with Alaska man, however all auto glass is safety glass of one kind or another.+
    – Ed Beal
    Jul 4 '18 at 19:25
  • 1
    Car windscreens are not tempered, just laminated, but all other windows are tempered. The polarization pattern is an intrinsic characteristic of the internal stresses in tempered glass, and I've updated my answer to reflect that.
    – user60561
    Jul 4 '18 at 20:03

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.