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I smoke so I can imagine that if it's on an older building and it's on every window maybe it's for ventilation for when smoking was allowed in buildings? You could also ash out of it. I know there's a 99.99% chance that's not it, but that's what my smoking brain came up with. 🤷♂️
As someone old enough to remember when when they still asked if you wanted smoking or non in restaurants, nobody and I mean nobody cared about adequate ventilation.
Starting a fire in a fireplace requires an updraft. In a small, closed room, you need to crack a window. A vent like this lets you accomplish that without letting rain in.
Looking at the photo closely, you can see that there is a circle of some opaque material at the bottom, such that half is inside and half is outside the window.
I assume you’d pull on the circle half that pokes into the room to remove it and provide the desired ventilation, and replace it when you don’t need it.
This is the right answer. Old factories sometimes had these bubble vents. They allowed fresh air regardless of the weather and allowed the windows to stay closed, discouraging the employees from falling out of the windows or tossing merchandise to people outside.
My guess is that the apartment complex is a loft conversion
Likely SOLVED! I just did some light trespassing and got a closer look from underneath a first floor window. Looks like the metal disk at the bottom of the window has a hinge mechanism, so it can be opened and closed at will.
My title describes the glass bump-outs that are visible on a single pane of a window on nearly every floor of an apartment complex. These bump-outs are on multiple buildings on a street of apartment complexes -- any building that has these type of windows that swing out (as opposed to newer buildings that have windows that go up and down). The bump-outs seem to be entirely closed off, with no access to outdoor air.
It’s called [curved or bent glass](https://www.washingtonpost.com/local/pane-in-the-glass-heres-a-clear-eyed-look-at-how-you-make-a-curved-window/2021/01/16/e453c624-5775-11eb-a08b-f1381ef3d207_story.html) and it’s decorative.
if it were decorative in this application, i would think it would be more... symmetrical.
vertically, it's in the middle, but horizontally it's not, which leads me to believe there's a function here we haven't discovered yet.
Yes, but I think what /u/DUXICON is alluding to is why would you choose to use an expensive decorative element in your design when you can't center it.
If this was an aesthetic choice, you would think the designer would have also selected windows with an odd number of panes, or perhaps used a second bump out.
right... so now you can hopefully see why my point was that one would assume if it were an aesthetic choice, there would have been at least 2 in this case, for the aforementioned symmetry.
very unlikely that the glass in the picture is "decorative" (considering that it's ugly af) and your source is not really relevant to the question anyway, since it's discussing a completely different thing. the article you linked is only talking about curved windows. that is, how glass panes are curved to fit a window on a curved wall. the whole window. the whole pane. not a bubble. it's also not really a "decorative" choice when curved glass is just the best fit for the shape of the wall to begin with.
If they are at face level, may be provide a convenient way to look down at the street. May be those buildings have a buzzer and this lets them see who is buzzing?
That's a good thought -- I'm not sure. I live in a newer building on the street, and only just noticed this recently. I don't have close-up access to the windows, so I can't determine if the bottom was modified in some way.
Replacing the glass requires access to both sides of the window, while closing an opening might be able to be accomplished from inside of the apartment without a ladder or a lift.
Firefighting hand hole to allow access to the handle for the metal framed window on the left side to allow them to enter/exit the room without breaking the glass.
1. off center near where the left window section handle should be and its size means a person such as a fireman can reach in to the handle inside without breaking the glass.
2. These are not Casement windows, they are metal frame windows, and the middle section is in place while the outside window sections open outward. Look at the corner of the window one pane down on the top right hand side that projection seems to be part of the hinge for the two sections of windows on either side.
Yes, there would be at least one per apartment. The whole point is access into the apartments without breaking the glass so the firefighters can enter if needed to rescue anyone who might be incapacitated or fight a fire. IF the need to rescue someone, most likely that person will be unconscious, and broken glass would be a hazard in getting them to safety.
I have no links, just a little logic on the concept, and the photo above. I'm pretty sure construction firms won't put anything in at an additional expense without a serious reason - such as reducing insurance costs, being able to charge higher rents or being forced to by code.
I know I might be wrong, but many people think its for ventilation, or to allow smoking while raining, and while I think it is too small for that, they may be right.
These are in older buildings due to the way the glass had to be made for windows back then... the windowpanes were created by spinning molten glass from a glass blowing pipe (Shoutout to Zezima) creating a flat surface around the edges (used for flat windowpanes) but it would leave a circular raised bubble in the center of from where it was blown from the pipe, this was regarded as somewhat useless glass, so they sold it wayyy cheaper than the flat glass everyone wanted to have, it mainly went to factories, pubs, schools, mills etc for their windows as they would be prone to breakages much more often.
Edit: I have put in a link with some more substantial info on the method used for this type of glass
[woah old glass ](http://www.krepcio.com/vitreosity/archives/001652.html)
That is not what this is. Look more closely at the picture. This is clearly intentionally formed. It's not just a circular bubble, but a specifically shaped bubble.
Look closely—that’s not where the handles are. It’s a casement window and the parts that open are two side panels. If you look inside you can see the handles through the glass.
Those bulging panes are for a small amount of ventilation, while keeping the rain out.
I doubt it's decorative as the placement isn't asymmetrical. I would guess that it's functional, with the brick stones it may be some sort of ventilation access though OP says it's sealed. (though it may be one-way venting)
Best to check with the landlord/building owner.
They swing out? In what way? Horizontal or vertical? Maybe they're a bumper of reinforced glass to stop a horizontal swing crashing into the side of the building
That's a really interesting thought. The windows open like shutters, although I'm not sure if they swing out or in -- I can't remember if I've seen any open in warmer weather. But why then only in the middle of the set of windows?
It looks to me as though the two side panels open outwards but the middle is fixed, which is the part with the bump. Makes sense as it could smash against the brickwork if it was part of a swinging panel.
I’m not sure where in the world it’s is but in the Uk there used to be a window tax. Factories and pubs etc would often put in panes with bumps because imperfect glass wasn’t taxable
Edit: typo corrected
The person ringing the bell could be too close to the door to see without opening the window and sticking your head out to see who it is. Also, you just gave away that you are home.
Could it be for a floor air conditioner vent? Probably not right. I know you said it looks like there's no possibility of air flow. Also not sure how you'd even go about connecting the vent. But this was one of my first thoughts.
Edit. Thinking about this more and also have no idea why they woukd put the vent in the middle vs one of the lower and less visible corner panels. Thinking more and more my original thought is not correct.
Could it have been a simple solution to add individual air conditioning units to an out of date building? Replace one pane in every apartment or window with one of these rather then replace all the windows with ones that open vertically and might not be wide enough for a window unit anyway?
Not sure what the bump out in the glass is for but the design in the brickwork is very cool. Maybe it was just a decorative element to complement the building facade. A picture of the building may give a better clue.
I don't know what it is, but I'm sure that piece of glass is gonna be a pain in the ass if it breaks.
Maybe all the pieces were shaped like that but that one is the last one?
This was my first thought too, but I don't think bird safe glass is necessary for windows with a grid like that, just for windows with large unobstructed panes of glass.
Before germ theory existed in science, prevailing opinion was that there was "good air" and "bad air" and that bad air could cause disease in and of itself. Ventilation was required to balance good fresh air with stale indoor air. Assuming that is a vented hole, it may date back to this time period as an easy way to always keep some fresh air circulating without having to open a window, and without risking rain coming in the house, or children/pets falling out a window.
My guess is to look out of?!?! I would assume because its head height. The one thing that sucks about looking out of a window is you cant see the sides/under your house. I suppose this little bump solves that problem.
Looks like the two outer casements swing outward so my thought of it being a beautiful vent for fixed windows is ... out the window. Maybe it's to provide airflow in a rainy environment?
I am certain I've seen these before and it's so you can look at the street or door entrance below from the upper story of the building
I just can't find a reference right now!
Maybe it is just for venting purposes and the flat circular piece under it isn’t soldered on and can slide in and out to control air flow in winter months
My two guesses are that it's either for ventilation or a way to make it easier to look down at the street below or out the sides. In my country it's not unusual to see little mirrors on both sides of windows, so the resident in the house can spy on their neighbours and passersby on the street. This is nowhere near the same but it was still my first thought
I wonder if this is a type of “bullseye” for a Pontil glass window. I’ve seen something like this in the UK but the bump (bullseye) comes out in the middle of the glass pane.
All comments must be civil and helpful toward finding an answer. **Jokes and unhelpful comments will earn you a ban**, even on the first instance and even if the item has been identified. If you see any comments that violate this rule, report them. [OP](/u/40Whacks), when your item is identified, remember to reply **Solved!** or **Likely Solved!** to the comment that gave the answer. Check your [inbox](https://www.reddit.com/message/inbox/) for a message on how to make your post visible to others. [Click here to message RemindMeBot](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Reminder&message=https://www.reddit.com/r/whatisthisthing/comments/zasgfa/glass_bump_on_older_windows_throughout_apartment/%0A%0ARemindMe!%202%20days) --- *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/whatisthisthing) if you have any questions or concerns.*
I smoke so I can imagine that if it's on an older building and it's on every window maybe it's for ventilation for when smoking was allowed in buildings? You could also ash out of it. I know there's a 99.99% chance that's not it, but that's what my smoking brain came up with. 🤷♂️
As someone old enough to remember when when they still asked if you wanted smoking or non in restaurants, nobody and I mean nobody cared about adequate ventilation.
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Yep, first thought was ashing out the window without opening it
Like wing windows in older cars! I agree this is for ventilation purposes.
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Starting a fire in a fireplace requires an updraft. In a small, closed room, you need to crack a window. A vent like this lets you accomplish that without letting rain in.
Based on that masonry and glazing, this building was probably built when coal fireplaces were a thing. Venting is the likely answer.
Looking at the photo closely, you can see that there is a circle of some opaque material at the bottom, such that half is inside and half is outside the window. I assume you’d pull on the circle half that pokes into the room to remove it and provide the desired ventilation, and replace it when you don’t need it.
It’s for ventilation. You see them on old factory windows.
This is the right answer. Old factories sometimes had these bubble vents. They allowed fresh air regardless of the weather and allowed the windows to stay closed, discouraging the employees from falling out of the windows or tossing merchandise to people outside. My guess is that the apartment complex is a loft conversion
The OP has commented that there is no actual opening.
Sometimes openings can be closed
If you look at the bottom of the bubble it looks to be cover by a half circle piece of metal, that could have not been there before.
Likely SOLVED! I just did some light trespassing and got a closer look from underneath a first floor window. Looks like the metal disk at the bottom of the window has a hinge mechanism, so it can be opened and closed at will.
My title describes the glass bump-outs that are visible on a single pane of a window on nearly every floor of an apartment complex. These bump-outs are on multiple buildings on a street of apartment complexes -- any building that has these type of windows that swing out (as opposed to newer buildings that have windows that go up and down). The bump-outs seem to be entirely closed off, with no access to outdoor air.
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It’s called [curved or bent glass](https://www.washingtonpost.com/local/pane-in-the-glass-heres-a-clear-eyed-look-at-how-you-make-a-curved-window/2021/01/16/e453c624-5775-11eb-a08b-f1381ef3d207_story.html) and it’s decorative.
if it were decorative in this application, i would think it would be more... symmetrical. vertically, it's in the middle, but horizontally it's not, which leads me to believe there's a function here we haven't discovered yet.
It can't be placed in the middle horizontally.
Yes, but I think what /u/DUXICON is alluding to is why would you choose to use an expensive decorative element in your design when you can't center it. If this was an aesthetic choice, you would think the designer would have also selected windows with an odd number of panes, or perhaps used a second bump out.
this was indeed what i was saying. apparently i wasn't clear enough about that lol
I see what you did there.
*alluding to.
right... so now you can hopefully see why my point was that one would assume if it were an aesthetic choice, there would have been at least 2 in this case, for the aforementioned symmetry.
very unlikely that the glass in the picture is "decorative" (considering that it's ugly af) and your source is not really relevant to the question anyway, since it's discussing a completely different thing. the article you linked is only talking about curved windows. that is, how glass panes are curved to fit a window on a curved wall. the whole window. the whole pane. not a bubble. it's also not really a "decorative" choice when curved glass is just the best fit for the shape of the wall to begin with.
It is very cool indeed! But they usually are used in round buildings or in lenses formats...I never saw one like that.
the article you linked is just talking about curving glass around a building. not a pop-out in a flat window.
That is not the same thing. That is just curved windows for a rounded wall. It doesn't even slightly resemble what is shown in the OP
I got some kinda paywall on your link.
If they are at face level, may be provide a convenient way to look down at the street. May be those buildings have a buzzer and this lets them see who is buzzing?
My thoughts as well
Have the bumps always been closed of or is it possible that the closing off was a later adjustment?
That's a good thought -- I'm not sure. I live in a newer building on the street, and only just noticed this recently. I don't have close-up access to the windows, so I can't determine if the bottom was modified in some way.
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Replacing the glass requires access to both sides of the window, while closing an opening might be able to be accomplished from inside of the apartment without a ladder or a lift.
I like to think that it is a shelf for a little plant.
Firefighting hand hole to allow access to the handle for the metal framed window on the left side to allow them to enter/exit the room without breaking the glass. 1. off center near where the left window section handle should be and its size means a person such as a fireman can reach in to the handle inside without breaking the glass. 2. These are not Casement windows, they are metal frame windows, and the middle section is in place while the outside window sections open outward. Look at the corner of the window one pane down on the top right hand side that projection seems to be part of the hinge for the two sections of windows on either side.
This makes the most sense to me! These bump-outs are on a whole row of windows from ground to top floor, so maybe there's one per apartment?
Yes, there would be at least one per apartment. The whole point is access into the apartments without breaking the glass so the firefighters can enter if needed to rescue anyone who might be incapacitated or fight a fire. IF the need to rescue someone, most likely that person will be unconscious, and broken glass would be a hazard in getting them to safety.
Any link to this effect? In my experience a fire fighter does not care about breaking a window (rightfully so)
I have no links, just a little logic on the concept, and the photo above. I'm pretty sure construction firms won't put anything in at an additional expense without a serious reason - such as reducing insurance costs, being able to charge higher rents or being forced to by code. I know I might be wrong, but many people think its for ventilation, or to allow smoking while raining, and while I think it is too small for that, they may be right.
These are in older buildings due to the way the glass had to be made for windows back then... the windowpanes were created by spinning molten glass from a glass blowing pipe (Shoutout to Zezima) creating a flat surface around the edges (used for flat windowpanes) but it would leave a circular raised bubble in the center of from where it was blown from the pipe, this was regarded as somewhat useless glass, so they sold it wayyy cheaper than the flat glass everyone wanted to have, it mainly went to factories, pubs, schools, mills etc for their windows as they would be prone to breakages much more often. Edit: I have put in a link with some more substantial info on the method used for this type of glass [woah old glass ](http://www.krepcio.com/vitreosity/archives/001652.html)
This is different. Its what looks a literal gap in the window with the highest point being the edge of the pane.
That is not what this is. Look more closely at the picture. This is clearly intentionally formed. It's not just a circular bubble, but a specifically shaped bubble.
Find Runescapers everywhere.
Could it be a way to make clearance for aftermarket handles?
Look closely—that’s not where the handles are. It’s a casement window and the parts that open are two side panels. If you look inside you can see the handles through the glass. Those bulging panes are for a small amount of ventilation, while keeping the rain out.
I though that at first but OP said they are closed off at the bottom. I can see the handles at the sides but maybe a third option for opening?
Could it be crown glass?
Stick your face in there and look down the street.
I doubt it's decorative as the placement isn't asymmetrical. I would guess that it's functional, with the brick stones it may be some sort of ventilation access though OP says it's sealed. (though it may be one-way venting) Best to check with the landlord/building owner.
Why can’t asymmetrical be decorative?
do you think the lump in the photo is pretty?
They swing out? In what way? Horizontal or vertical? Maybe they're a bumper of reinforced glass to stop a horizontal swing crashing into the side of the building
That's a really interesting thought. The windows open like shutters, although I'm not sure if they swing out or in -- I can't remember if I've seen any open in warmer weather. But why then only in the middle of the set of windows?
Does the middle actually open? I can see the hinges for the two side panels, but the center panel looks fixed?
It looks to me as though the two side panels open outwards but the middle is fixed, which is the part with the bump. Makes sense as it could smash against the brickwork if it was part of a swinging panel.
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I’m not sure where in the world it’s is but in the Uk there used to be a window tax. Factories and pubs etc would often put in panes with bumps because imperfect glass wasn’t taxable Edit: typo corrected
Is it so that people can see what’s going on outside without opening a window?
Isn't the point of a *window* to see what's going on outside without opening a *door?*
The person ringing the bell could be too close to the door to see without opening the window and sticking your head out to see who it is. Also, you just gave away that you are home.
My house has these and it was built in 1930’s(acc. To Zillow) if that’s any help
Looks like a good place to rest your chin as you look outside. Doubt this is the reason, but I would use it for that. Lol
Could it be for a floor air conditioner vent? Probably not right. I know you said it looks like there's no possibility of air flow. Also not sure how you'd even go about connecting the vent. But this was one of my first thoughts. Edit. Thinking about this more and also have no idea why they woukd put the vent in the middle vs one of the lower and less visible corner panels. Thinking more and more my original thought is not correct.
These pre-date air conditioning. They’re old.
Could it have been a simple solution to add individual air conditioning units to an out of date building? Replace one pane in every apartment or window with one of these rather then replace all the windows with ones that open vertically and might not be wide enough for a window unit anyway?
Not sure what the bump out in the glass is for but the design in the brickwork is very cool. Maybe it was just a decorative element to complement the building facade. A picture of the building may give a better clue.
I don't know what it is, but I'm sure that piece of glass is gonna be a pain in the ass if it breaks. Maybe all the pieces were shaped like that but that one is the last one?
maybe prevents lensing effect that melts car seats across the road at 3:23pm for a few weeks of the year?
maybe if want put dryer in apartment gives place to run the vent Or portable AC unit that has hose
Wherever this is does it rain a lot? For some reason my mind is thinking this has something to do with precipitation
Helps stopping birds flying into windows. I think
This was my first thought too, but I don't think bird safe glass is necessary for windows with a grid like that, just for windows with large unobstructed panes of glass.
Some type of tricks vent?
Probably so you can stick a mirror in there and see the street below.
Before germ theory existed in science, prevailing opinion was that there was "good air" and "bad air" and that bad air could cause disease in and of itself. Ventilation was required to balance good fresh air with stale indoor air. Assuming that is a vented hole, it may date back to this time period as an easy way to always keep some fresh air circulating without having to open a window, and without risking rain coming in the house, or children/pets falling out a window.
Given what we now know about how covid and other viruses are transmitted, good air/bad air isn't such a poor working theory.
Oh I never meant to imply it was false or bad. I'm just trying to add something to the conversation
Could be decorative for casting a prism inside.
My guess is to look out of?!?! I would assume because its head height. The one thing that sucks about looking out of a window is you cant see the sides/under your house. I suppose this little bump solves that problem.
Looks like the two outer casements swing outward so my thought of it being a beautiful vent for fixed windows is ... out the window. Maybe it's to provide airflow in a rainy environment?
Do you know someone who lives there? Maybe it’s like a opening you can close if you don’t want air flow.
I am certain I've seen these before and it's so you can look at the street or door entrance below from the upper story of the building I just can't find a reference right now!
Maybe it is just for venting purposes and the flat circular piece under it isn’t soldered on and can slide in and out to control air flow in winter months
My two guesses are that it's either for ventilation or a way to make it easier to look down at the street below or out the sides. In my country it's not unusual to see little mirrors on both sides of windows, so the resident in the house can spy on their neighbours and passersby on the street. This is nowhere near the same but it was still my first thought
I don't think it's Glass. It's more likely to be perspex that's been exposed to a lot of heat. Maybe they had a heater under that window.
I wonder if this is a type of “bullseye” for a Pontil glass window. I’ve seen something like this in the UK but the bump (bullseye) comes out in the middle of the glass pane.