• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). There are daily reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Vacuum Insulated Window Glass

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
Reducing background noise is one of the most effective means to improve domestic audio quality, as we all know when we listen late at night. Apart from various appliances such as heating systems, the biggest problem is external noise from traffic. Current double glazing can help, and particularly if designed for optimum sound proofing, by having two glass sheets of different thickness and with a somewhat wider cavity between them. This does not really cost much, and it helps, up to a point.
The quest for better thermal insulation has recently become much more important with our concern about global warming, and now also rising heating bills. So people have increasingly begun to use triple glazing for better thermal insulation, and sometimes this is mandated for new construction. Unfortunately the resulting package is thick and heavy, usually requiring new window frames when applied to existing homes. That is expensive, and often ugly, particularly in nice old houses (or modern ones like ours where the architect was very particular about the slim design of the window frames). So the glass industry has now come with an alternative: vacuum insulated double window glass. This has an ultra thin cavity that is no longer filled with some noble gas, but is a vacuum, like a thermos bottle. This new glass has a thermal insulation that is at least as good as triple glass, or even better, is much thinner and lighter so will fit in historic houses, very hard to break for burglars, and it also, and that is why I am posting on a audio forum, has much better sound proofing properties.
There are three disadvantages, and I suspect that all three will be largely temporary. First, it is a new technology, so there may be quality problems that will only surface in the future. However, manufacturers seem willing to give a fifteen year warranty. Second, thus far really large windows are impossible, so in our case we shall have to wait. Third, the glass is still expensive, although in practice it may well be cheaper than triple glazing if that would require new window frames.
 

JSmith

Major Contributor
Joined
Feb 8, 2021
Messages
2,921
Likes
6,545
Location
Algol Perseus
So the glass industry has now come with an alternative: vacuum insulated double window glass.
I didn't think this was anything new?

what-is-vacuum-glazing.jpg




JSmith
 
OP
W

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
True, from what I read various companies have been working on this for a number of years, but it seems it is only now getting more traction. I have been looking into better double glazing for a while as our current and pretty decent double glazing is now 24 years old, and I just noticed this option for the first time. Equally, it is rarely ever mentioned in current discussions of better thermal home insulation. We have just finished a major home insulation project with our 24 year old modernist house, and after some research and external advice decided to leave replacing the window glass until technology had improved even further and there would be something that insulates a lot better than what we have now and would still fit our elegant slim window frames. So I was pretty excited that there is now something that nobody had mentioned to us, even if as yet the glass is not available for most of our rather larger windows. And the sound proofing benefits are an unexpected benefit, even for a residence in a leafy suburb.
 

BJL

Member
Joined
Mar 11, 2022
Messages
36
Likes
30
I have windows 7/16" thick, two layers of glass laminated to some kind of plastic interlayer. This provides excellent sound reduction compared with conventional glass. Insulated windows described in the first post wouldn't work for me here in a hurricane zone, they are too delicate, but using heavier glass with an interlayer blocks most sound. This is an important (for me) side benefit to the primary purpose of protection from hurricane force winds and flying objects. I would use windows of this type even if I lived outside of a hurricane zone, and perhaps insulated as well, if safe.
 

BlackTalon

Senior Member
Joined
Apr 14, 2021
Messages
302
Likes
466
Location
DC
Make sure to read up on the expected U-value retention over time. With the vacuum insulated roof insulation panels they can lose 50% of the insulating value over 25 years.
 

DVDdoug

Major Contributor
Joined
May 27, 2021
Messages
1,240
Likes
1,532
Theoretically it seems perfect! But the supports between the layers are probably "better" at transmitting vibration than air (or other gas). With full atmospheric pressure the pains would bend together and touch, or break if they are far-enough apart.
 
OP
W

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
I would use windows of this type even if I lived outside of a hurricane zone
We don't live in a hurricane zone. although our climate is changing and we now sometimes have very strong winds. The advantage of these vacuum windows is, of course, that they can be used in existing slim window frames. And they sport very high insulation values, which is crucial in this day and age.
 
Last edited:
OP
W

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
Make sure to read up on the expected U-value retention over time.
The EU has recently formulated standards for this kind of glass. From what I understand experts expect these windows to last longer than traditional double glazing.
 

Hipper

Addicted to Fun and Learning
Joined
Jun 16, 2019
Messages
741
Likes
603
Location
Herts., England
I added a third layer of removeable glazing to existing conventional double glazing (which I understand is air filled) and measured the sonic results - see my post 25:

https://www.audiosciencereview.com/...w-quite-is-your-room.15922/page-2#post-511337

The gap between the double and third layer is about 20cm. It doesn't stop the low noise from buses or lorries (which I don't notice when listening to music), or boy racers and motorbikes, but it does allow me to hear significant improvements in the finer details of music - percussion for example. I highly recommend it for those living on busy roads.

https://clearviewsg.co.uk/wp-content/uploads/2018/06/3-Panel-Horizontal-Slider.pdf

I had 6.4mm glazing fitted in the reveal.

Of course if your existing glazing is coming up for renewal it would certainly be worth considering this vacuum filled system. However with double glazing it is not just the glazing that could be an issue. The rubber seals can deteriorate over time and somehow the hinges can be warped or otherwise damaged such that windows don't close properly, both allowing in drafts and therefore sound too. That's my experience anyway.
 
Last edited:

MinMan

Member
Joined
Nov 1, 2020
Messages
39
Likes
34
The conventional method of reducing sound transmission through glass includes at least one layer of laminated glass. Performance is specified by STC ratings with higher numbers transmitting less sound. https://www.soundproofwindows.com/stc-ratings/
I have worked directly with a few of acoustical engineers - all will agree with this assertion.
 
Last edited:

Lambda

Major Contributor
Joined
Mar 22, 2020
Messages
1,606
Likes
1,339
I thought all modem windows are filed with low pressure inert gas.
At what point a low pressure is called vacuum is arbitrary.

But a significant vacuum would cause lot of force over large area windows.
 

sq225917

Major Contributor
Joined
Jun 23, 2019
Messages
1,043
Likes
1,138
It's just lower than atmospheric pressure, it's not a vacuum as in 0mg Mercury.
 

Lambda

Major Contributor
Joined
Mar 22, 2020
Messages
1,606
Likes
1,339
It's just lower than atmospheric pressure, it's not a vacuum as in 0mg Mercury.
But technically nothing is ideal vacuum. not even space.
So at what point call it "vacuum"?

In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is considerably lower than atmospheric pressure.
In Marketing and promotional material vacuum refers to any pressure slightly lower than atmospheric pressure.
 
OP
W

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
Traditional double glazing uses inert gas, but in this case a vacuum, just like in a modern vacuum Thermos bottle. Will it be a theoretically perfect vacuum, no, of course not, but how much does that matter? The measured thermal and sound insulation numbers of the most recent versions of the technology are pretty impressive (U=0.4). Seals are glass solder, and are expected to outlast the various seals used on traditional double glazing. I am sure there are other technologies to produce even better sound insulation, but this is primarily for better thermal insulation such as we are now all desperately looking into, with rather better sound insulation as a bonus (-36 dB), and also for use in existing window frames. Our own double glazing is now 24 years old (U=1.4), and we already had to replace one large window. So I know the rest may well have to be replaced sometime over the next five or ten years. Triple glazing is the new norm (and mandated for new houses in the Netherlands), but usually demands new and heavier window frames. That is not only expensive, but in our case would look pretty ugly in a very sharply designed modernist house. So I have been keeping an eye open for new emerging technologies, and found this one that both serves to give just about the best thermal insualtion currently possible, but also rather better sound proofing than traditional double glazing.
 

kthulhutu

Active Member
Joined
Mar 15, 2022
Messages
105
Likes
85
Unfortunately, this is all a bit useless to me as air quality is important so I always have a window open. Otherwise I get CO2 levels in excess of 2000 ppm.
 
  • Like
Reactions: BJL
OP
W

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
Of course I agree with you that air quality is important, and I know nothing about your situation, but 2000 ppm is certainly far too much. Modern Dutch houses have a mandatory central ventilation system and sound insulated ventilation openings, mostly in the window frames. Research has shown that a large proportion of CO2 production in the home is the product of cooking on a gas stove. As part of our project to transition to a heat pump system for heating our home instead of using a gas boiler, we have already replaced our gas stove with an electrical induction stove (while we are waiting for a heat pump, but those are currently in short supply). This also significanrtly reduces the quantity of fine particles. The resulting improvement in air quality is obvious, and was indeed predicted by research. You do need new pots and pans, however.
 

BJL

Member
Joined
Mar 11, 2022
Messages
36
Likes
30
Unfortunately, this is all a bit useless to me as air quality is important so I always have a window open. Otherwise I get CO2 levels in excess of 2000 ppm.
I agree with this as a general statement. I've never tried to measure CO2 or other pollutants, but I always leave a few windows cracked open a an inch or two, when using A/C. This doesn't cause any noticeable increase in electric use and it improves the indoor air. The heavy duty windows still reduce outside noise considerably, but I certainly agree that to prevent indoor air pollution it is best to have some cross ventilation.

I don't use any gas appliances, but simply cooking, even on an electric stove, will create indoor pollution. I have air purifiers strategically placed (to cover the entire house), and frequently when cooking their sensors go red to indicate particulate pollution, and the fans go high.
 

kthulhutu

Active Member
Joined
Mar 15, 2022
Messages
105
Likes
85
Of course I agree with you that air quality is important, and I know nothing about your situation, but 2000 ppm is certainly far too much. Modern Dutch houses have a mandatory central ventilation system and sound insulated ventilation openings, mostly in the window frames. Research has shown that a large proportion of CO2 production in the home is the product of cooking on a gas stove. As part of our project to transition to a heat pump system for heating our home instead of using a gas boiler, we have already replaced our gas stove with an electrical induction stove (while we are waiting for a heat pump, but those are currently in short supply). This also significanrtly reduces the quantity of fine particles. The resulting improvement in air quality is obvious, and was indeed predicted by research. You do need new pots and pans, however.
It's a 30 year old or so small British house with pretty poor ventilation, no fancy A/C or central ventilation systems. I would love to get a vent for my listening room at least so I don't have to deal with the increased noise floor but I'm not sure of the cost or considerations of doing it yet.
 
OP
W

Willem

Major Contributor
Joined
Jan 8, 2019
Messages
2,907
Likes
4,354
It's a 30 year old or so small British house with pretty poor ventilation, no fancy A/C or central ventilation systems. I would love to get a vent for my listening room at least so I don't have to deal with the increased noise floor but I'm not sure of the cost or considerations of doing it yet.
Such measures though effective are rarely economical until the window glass/heating system/roof insulation etc have to be replaced anyway. But it is worth being aware that if and when such moment occurs, there is new technology, and particularly now that we all have to cut our use of fossil fuel. Current prices for oil and gas are certainly a painful incentive. When I first did the sums for a new heating system the economic case for a heat pump based all electrtic system was marginal, but I expected rising fuel prices. By now at Dutch pirces you earn back the investment in a heat pump in four or five years. The same logic also applies to insulation.
 

BJL

Member
Joined
Mar 11, 2022
Messages
36
Likes
30
It's a 30 year old or so small British house with pretty poor ventilation, no fancy A/C or central ventilation systems. I would love to get a vent for my listening room at least so I don't have to deal with the increased noise floor but I'm not sure of the cost or considerations of doing it yet.
There's another approach vs. A/C, if it is practical for you. I also have a ceiling fan in my listening room. It is nearly silent, but even operating a low or medium speed, it is sufficient to draw fresh air with a couple of windows open just a couple of inches. I use it frequently when A/C isn't needed and during the week or two when I have to heat the house.
 
Top Bottom