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Double or Triple Glazed Windows?

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(@trbob)
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Topic starter  

Firstly, apologies I cannot see an appropriate place to post this, I'm going with ASHP as that is what I have.

So far in our 1983 built house which we renovated and moved into last year we have replaced the two front bedroom windows with modern double glazed units, as they were letting air/noise in, one could just be opened even when locked. The rest of the house is double glazed with what looks to be quite old double glazed units which are ok for now but we aim to do everywhere as we can afford it.

When I started the renovation I was warned off triple glazing as apparently modern double is almost as good and is lighter/cheaper. I've read all sorts of different view points online and am interested to hear from people with ASHP.

The recent cold snap highlighted what needs to be done as a priority;

The lounge, a bay window - thinking about doing away with if it's not too much hassle as the top and bottom will not be insulated, gets condensation the worst by far. At the other end is a north facing, sliding patio door with metal frame that gets condensation. When we replace, we're not sure what to go with, bi-folds are nice, but I hear that they are very expensive. Personally I'm not that bothered about having the whole space open in summer.

The main bathroom, north facing window, two external walls, it got noticeably colder compared to the other upstairs rooms (the en-suite next door being the main basis for comparison) despite having a large new radiator that does get hot. I am considering a triple glazed unit here if no where else.

To address the condensation I mentioned, since the temperature dropped we got really bad condensation on the windows, so I got a heated PIV installed which cured the upstairs overnight, even when set to full which is supposedly for a much bigger home we still had a significant amount downstairs, so I've set it lower so that it keeps upstairs clear. My gut tells me that it's the old cold windows that are the issue, not the PIV as my study (was internal garage and now probably the most well insulated room in the house) which has a brand new double glazed unit is always bone dry and doesn't get overly warm as the radiator is at the end of the heating loop. Also we have powerful extractors in the bathrooms and always use the extractor when cooking. I've tried using the de-humidifier downstairs, but its reading a pretty low humidity after a short period.

 

Mitsubishi Ecodan 8.5kWh
4.4kW Solar PV
5.2 kWh Battery Storage
1983 build, 300mm loft insulation, cavity wall insulation (beads)


   
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(@bob77)
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292 kWhs
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In our recent renovation we put in triple-glazed bifold doors and I have been very impressed. During the recent cold spell there was frost on the outside of the glass which didn’t melt for several days, while the inside pane of glass didn’t even feel unpleasantly cold to the touch. 

They weren’t cheap though (about £3600 for a 2.1 metre 3-door unit) although I don’t believe triple glazing added a huge amount to the cost. 

My previous point of comparison was horrible 30 year old aluminium sliding doors which were constantly dripping with condensation in winter due to cold bridging problems. 


   
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(@batalto)
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Our upstairs is triple glazed and the windows are noticeably warmer to the touch than the downstairs double glazed. Only a few years between them, so I'd say very comparable. 

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
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(@benseb)
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Posts: 104
 

We're in the process of replacing all of ours. They are about 18 years old and whilst some are still ok, some aren't so we're going to do them all at once

We're replacing with Triple - my thinking is do the best you can now, as it will probably become the norm in the next 10 years or so (and already is in colder climates)

However we did find some companies sell 3x glazing and its not much better than 2x. We went to Green Building Store and they only sell 3x and it's very good - so just be careful to compare the U values to check what you're getting.

250sqm house. 30kWh Sunsynk/Pylontech battery system. 14kWp solar. Ecodan 14kW. BMW iX.


   
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 robl
(@robl)
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We changed the glass in our circa 1990 uPVC windows 11 years ago.  The double glazing units that were in were the standard of the time: 4mm glass/16mm air /4mm glass, aluminium spacer, air fill - giving a pretty ropey (by todays standards) Ug of 2.6W/m^2/degC with a lot of cold bridging, but all of the frame still seems fine. 

The replacement sealed glass units are 4/16/4, insulating spacer, argon fill, St Gobain Planitherm 1 coating on the inner pane - this is a "softcoat" giving an overall Ug-value of 1.0.  I think it's still pretty much the best that you can get, barring replacing the frames to get a bigger gap, and fitting 3G.  The plastic frames and windowsills themselves are now mostly foam filled by me, to improve their insulation further - being very careful not to fill anything associated with keeping the DG unit seal exposed to outside air, for a good long life.  Pilkington make a similar "softcoat", but I couldn't find anyone that would sell it - I was only offered Pilkinton-k, which is not quite as good.

Pilkington and St Gobain have free calculators, that will work out the glass performance of the glass - U value, clarity, sound attenuation, UV.  The St Gobain one now even gives the upfront CO2 emissions for making it.

https://calumenlive.com/

https://spectrum.pilkington.com/Main.aspx


   
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(@bretix)
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It's funny how things come around but we are just about to have new windows installed and have been told that new regs are that they must now have vents on them.

We were also told by 3 different salesman that there would be no great benefit going to triple glazed unless we lived near a road or noisier environment.

Windows getting replaced are about 20 years old with the seals degraded leading to condensation so if new windows don't help, I'll be changing my extractor fan to a blauberg decentralised MVHR unit to get rid of humidity in the bathroom.

2 10kw Grant Aerona3
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(@jpst21)
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We’ve changed the majority of our windows to triple glazed.

The original windows were only 11 years old but hardwood and had been neglected by the previous owner.  They were however very high spec units being 22mm rather than 17 or 19

The difference is phenomenal for insulation and sound with the added benefit of improved security 

I have a thermal picture I’ll dig out as that shows the heat loss difference as @bob77 above we had frost on the outside that didn’t melt even with 23 degree internal temperatures 

another plus for us on the south facing side was slightly lower solar thermal gain from triple as we have a lot of glass on that side and it’s too hot in the summer 

 

edited to add the cost difference was 12% over double glazed

pictures attached, see the heat loss through 100mm hardwood and 22mm glass compared to the triple unit on the same room 

374B40CF CF34 4988 BD5B 270EBE87D918
DD7A99B7 27DE 40DC A1F6 0A82A462A426
CF1F5772 9D2A 4A7E 9186 491B6FB575F0

 


   
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(@trbob)
Trusted Member Member
254 kWhs
Joined: 1 year ago
Posts: 29
Topic starter  

Thank you all for the replies and information, food for thought, interesting JPST21, a cost difference of 12% over double glazing, I suspect that the insulating properties will be greater.

Mitsubishi Ecodan 8.5kWh
4.4kW Solar PV
5.2 kWh Battery Storage
1983 build, 300mm loft insulation, cavity wall insulation (beads)


   
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