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Does Triple Glazing Make Sense?

Bit by bit, we are being encouraged to switch from double to triple glazing. You may not have noticed yet but the pressure is on to improve the energy performance of windows and we are now reaching the stage where mere double glazing will no longer be enough.

The rough and ready method of comparing the energy performance of windows is to use the U value measurement, just as we do with walls, floors and roofs. Traditional windows, with a single pane of glass in them, have a U value in excess of 5. Double glazing used to score over 3, but, over the years, the manufacturing process has undergone a number of improvements and currently the Building Regulations insist that any window you install today should have a U value no worse than 1.6.

These improvements have been brought about by the introduction of:

  • Wider cavities between the two glass panes 16mm is the optimum distance
  • Low-emissivity coatings being added to the glass to stop heat escaping
  • The cavity being filled with an inert gas, usually argon
  • Designing out cold bridges, such as aluminium spacers, surrounding the glazed units

Now, a U value of 1.8 may look good when compared to what we have been fitting relatively recently, but compared to the U value demanded for walls – currently less than 0.3 and due to fall even lower – you can see that windows remain weak spots in the overall thermal efficiency of a building envelope. Hence the tremendous pressure to improve their performance even further.

(MORE: Buyer's Guide to Rooflights)

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Should we switch to triple glazing?

Opinion is divided. Triple glazing is widely used in cold climate countries like Sweden and Norway, and the ultra-low energy PassivHaus standard requires triple glazed windows with a U value of no more than 0.8. To get a window with such a low U value, you have to not only switch to triple glazing but also insulate the frame itself, as well as using more expensive manufacturing techniques — the gas krypton tends to be used, instead of argon.

(MORE: Choosing Window Frames)

Now, though a U value as low as 0.8 sounds very impressive, the additional energy we are saving is minuscule whilst the payback time for triple glazing (like double glazing) is high compared to other energy-efficiency improvements. But there is a little more to it than this. 

The key benefits are really to do with comfort. If you insulate the walls, roof and floor of a house, and you ignore the glazing, you end up with cold spots surrounding the windows at night, which cause draughts, draw heat away from you if you sit next to them, and result in streams of condensation running down the panes. So, in essence, the standard of glazing has to match the standard of the insulation elsewhere in the house, so that the warm wrapping around the house performs consistently.

(MORE: How to Solve Condensation)

Which is where triple glazing comes in. Because if double glazing makes a modern house more comfortable to live in, triple glazing makes it even more so.

The physics involved here have been worked out in Germany by the PassivHaus Institute. It has shown what happens to surface temp­eratures on various forms of glazing when it gets really cold outside, and the internal air temperature is designed to be at 21°C:

  • Next to a single glazed window, the internal surface temperature is around 1°C.
  • Next to a double glazed window (2000 vintage), the surface temperature is around 11°C.
  • Next to a modern, energy-efficient double glazed window, the surface temperature is 16°C.
  • Next to a triple glazed window, with a centre-pane U value of just 0.65, the temperature is 18°C. 

So you can see that whilst a double glazed window is perfectly adequate, a triple glazed one is just that much more comfortable, because it hangs onto heat just that little bit better. So whilst triple glazing may make little difference to your heating bills, you will notice the difference inside the house.

The PassivHaus standard promotes the use of triple glazing for precisely this reason – i.e. comfort – although it also states that the frames themselves have to be insulated, and the windows need to be mounted in the correct location within the wall assembly.

Heat Absorption

To make things more complex, windows behave rather differently to walls and roofs in that, when the sun is shining, they are capable of absorbing heat. In fact, the very best double glazed windows are already capable of being net heat contributors over the course of a heating season. In contrast, triple glazed windows slightly reduce the heat absorption characteristics of a window.

To reflect these complexities, the British Fenestration Rating Council has devised a scheme for the energy labelling of windows, from A down to G. The top rating is reserved for windows that are reckoned to absorb as much heat as they lose, and they include both double and triple glazed windows.

The upshot of this is that there are many who argue that triple glazing simply doesn’t make sense in a climate like ours. Triple glazing is more costly to produce, produces much heavier sections and has an embodied energy approximately 50% higher than double glazing.

So why are we even thinking of going triple glazed? It’s all to do with the Code for Sustainable Homes, which the Government is using as a roadmap for us to move towards building zero-carbon homes by 2016. The Code more or less requires us to adopt the ultra-low-energy PassivHaus standard which demands windows with a U value no higher than 0.8 — triple glazing with insulated frames.

(MORE: What is the Code for Sustainable Homes?)

(MORE: CSH: How to Meet the Requirements)

 

Will it stop there?

Window manufacturer Scheiwiller in Switzerland is producing quadruple glazing (i.e. four panes; three cavities). There are, however, technical problems with simply adding more and more panes of glass: not only does the resulting window become ridiculously heavy, but the additional panes stop light coming through. In fact, in terms of energy efficiency, there may even be a fall-off as the amount of sunlight the window can absorb is reduced.

It is more likely that future developments in window technology will evolve around new coatings, or phase change materials which absorb heat in sunlight and release it at night. Look out for GlassX, produced by another Swiss company, which is already manufacturing a product that does this.

An alternative option that might make more sense is to revisit the traditional practice of drawing curtains across windows after dark. It may be low-tech, in comparison with glazed cavities filled with krypton, but it’s something of a natural British habit and it does cut down on heat loss. Perhaps it’s time we paid attention to improving the heat retention characteristics of curtains and blinds, rather than continuing to engineer glazing units to ever lower and lower U values.

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49 Comments

I read a blog today on a triple glazing website, well it broke down the U-Value method used to measure how energy efficient windows are. Now i am looking to get my windows done and Sureglaze say they sell a 0.8 triple glazed window but can achieve a 0.7 for me for an additional cost, if i am going to buy windows then i definitely want the best as i don't plan to replace them all the time, so does anyone know if i can get a U-Value lower than the 0.7. This is the information i read on this website http://sureglaze.co.uk/triple-glazed-windows/. It’s best I have found so far in England, going to do some more research before calling anybody out for quotes.

Triple glazing is in deed part of the solution. but what's the point in triple glazing when you have a massive chimney leaking all your heat into the sky or when you have breeze blowing in under your door or skimpy insulation in your attic?

Passive houses are the way forward and triple glazed argon filled windows are a big part of passive house construction. So if you are building a passive house or own a very well insulated, air tight house, then yes, triple glazing is the way forward for you and it will result in great energy savings and money saving

If you Live in the USA and want triple glazed windows that have ben constructed to a Passive house standard but you don’t want to pay an extortionate amount of money, then I would strongly recommend buying from Klearwall - Triple glazed windows for passive houses.

It might not be worth it for heat insulation but what about noise reduction? I am considering it for this purpose. Any comments?
Just had triple glazing installed and noticed that the windows have a noticable blue tint from the outside? The windows have a u value of 1.3. Is this normal? Not really keen on having blue tinted windows. I'm assuming that the windows have a thermal coating but should it be so noticeable?
First point: It wasn't updated in December 2011, unless you have a good handle on time travel. Second point: The section comparing the inside temperature of different types of glazing systems when the outside temperature was 'really cold' would have been even more helpful if you had told us the actual outside temperature. My final point is to do with the conclusion at the end - basically saying stick with double glazing and pull the curtains - which in my opinion very simplistic and confusing. This outgoing winter, even in the south-east of the UK we had consistent daytime temperatures of minus 5°C; it must have been much lower in the north of the country. It's medieval to suggest that we all draw the curtains during the day to keep comfortable. And what about the problem of condensation that you actually touched on earlier in the article? Closing the curtains is not going to stop that, day or night. Personally I've got a choice to make about the type of glazing I want in my extension to make it 'future proof'. 2°C doesn't sound a lot when comparing double and triple glazing inside glass temperatures, but you try turning down the heating by 2°C and you soon notice it - it's tangible. I almost wrote off triple glazing after reading the article, but after some thought I've decided to pursue it further. Of course it's going to be more expensive, but the thermal and acoustic advantages make sense - it just depends on the cost. The more we demand it, the more likely it is to reduce in relative cost over time. Sorry if I went on a bit. Thanks, Nick.
I can agree with the argument for triple glazing in Passive houses. In England, a vast proportion of domestic window installations require trickle ventilation to comply with FENSA/Building Regs, so to install triple glazing into a building where trickle ventilation is required - is this not just ridiculous? I sometimes cannot see the point in even installing fantastic A Rated double glazed windows, with good thermal and accoustic qualities, only to be told we must route a great big hole through the frame and fit a flimsy cover over it!? Many people want great A rated windows, only to have to install trickle vents which surely defeats the object? I have seen curtains blowing from the drafts through trickle vents on cold windy days, when the windows fitted are still technically stamped as A Rated. It seems to me that the Building Regs for Insulation and Ventilation are tripping over themselves, making a solution sometimes impossible. Until a better solution is reached for this area of the market (Im talking about your average 3 or 4 bed house, not an architect designed £500K type) I find it hard to even contemplate triple glazing.
Guys I retrofitted the Alfa GE quadruple glazing window from Skaala into my UK home. It has come in handy in this weather. I am fully quadruple glazed. My doors are from France. The U value for the windows is 0.7 throughout and for the doors it is 1.8 Daniel
The noise reduction is unbelievable over double glazing. I did a thorough study of noise and know almost everything, for I bought the windows principally for noise reduction (42 dB at a basket of frequencies) it is all tested by Skaala in Finland. Now they pay off for heat insulation. I live in Worcestershire and it was -14 C last night. I installed the windows last year right in time for Christmas and the benefits are enormous. When you re-trofit to a UK home there are some issues. You need to do it plasteboard to plasterboard rather than brick to brick I can explain it all. Send me your email and I can give you advice. Write to dr.daniel.howard AT gmail
hi i have recently had triple glazing installed on some of the windows in the morning and the evening there is a line of condensation along the bottoms of the windows but in some rooms its dripping on to the window sils is this normal or should this not be happening
It's good to see triple glazing is now becoming more mainstream in the UK and it's about time. I live in Bradford and live quite local to the Sureglaze factory; I have had triple glazing from them about 5 years ago. Was reading through the posts and was surprised to see their name come up, their website used to be sureglaze.com when i had my windows and doors done but it's the same company as I checked the www.sureglaze.co.uk out, same logo etc, just looks better so i guess they just changed web address. Considering i had my triple glazing done quite some time ago it is brilliant, very energy efficient and sound proof. Some guy above mentioned they've had it in Sweden for over 10 years so it's about time it got more mainstream in the UK. I think there is also a few more companies offering triple glazing now so it gives us more of a choice but quality wise Sureglaze are brilliant and if you’re looking for triple glazing or just windows and doors in general then they’re a good established company to use. I can't see anyone having a complaint as their quite a big setup and have a quality service. Either way i think triple glazing should have been mainstream in the UK a long time ago, i mean we get enough cold weather to justify it and it's much better all round except on price but that is to be expected compared to double glazing.
Got an idea to buy a house in France-- Down to -13 in winter-time Thanks for all your comments ..It will help me to decide HOW to combat the problems I know I will get! Triple glazing AND secondary seems the answer to me from all your comments Thankyou all Terry
Forgot to mention House is next to a main road also
thanks for your input a very important decision on double or triple. nice one. double for me.
I dont understand your review. You start by saying triple glazing is a waste of time as there are negligble benefits, yet contradict that with emprical data that suggests you actually get more than twice the heat loss from double glazing. You then reinforce your contradiction by suggesting people pull thier curtains instead, once again pointing to the fact that heat is lost through the window area. Are you trying to tell us that in Winter, when in a country which sees little sun at the best of times, triple glazing absorbing sunlight is a factor? Ive never heard such utter tosh. Then factor in windows which dont even face the sun. I reckon you must be a double glazing, or energy salesman. With the cost of energy garanteed to rise, anything that reduces consumption is a winner Finally, if there were so little to gain, then why do all the scandinavian countries already have it?
I've just recently had 5 windows and a secure fire-rated front door installed in my London flat by Rawington. I did a lot of homework on price vs quality and had many sales reps through my front door. Rawington blitzed them all in all levels of service and product. A major factor for me was customisation and triple glazing. I received colour and stain charts with loads of options, even for the handles. I live near by Brixton Road so security and noise control were major issues for me. I now live in a silent, mini, Fort Knox, and the window frames match the colour of my interior decoration!
Road in front of house very noisy. I have 15 year old double glazing with shutters inside. I'm considering treble glazing but am unsure if I will gain marked improvement in significant decibel reduction for the cost? Any comments welcome.
I lived in Sweden 1983-84 where I was told triple glazing was made mandatory in 1973 (!) after the Yom Kippur war and the first oil crisis. The two cavities were of different widths - one wide (40mm or so I think) for better sound insulation. Interestingly in the kitchen, above the solid fuel Raeburn was an extractor hood and warm air out of the kitchen passed through a heat exchanger, fresh air being drawn in from the loft space in winter, and by operating a simple flap, cool air drawn in from outside the house - on the North side, in summer! The insulation, loft, walls and floor, was unbelievable, and doors almost hermetically sealed, so no draughts. Going back to Edinburgh was a shock. I live in Tasmania at the moment the winters being like Scottish summers.
I have to make an iminent decision whether to go for double or triple glazing.We want a large area of glass (poss 2.3 x 2.6m)There seem to be so many things to consider and don't know which way to go. Floor and walls of the new kitchen/diner will be very well insulated. We will have underfloor heating (does this make a difference?) It seems the weight of the German triple glazed product we are looking at would indicate we have to have a smaller area of glass than we hoped for. Anyone got anything to add to the debate.
Is buying a new car makes sense? you loose 30% of value after one year. PEOPLE STILL BUY THEM. Why not to waste money on tripple gaze and have no condensation and cooler place in the summer?
I concur with most of the comments made here. However, it does ignore several basic important factors. Insulation of window areas is considerably lower than wall areas, and the absorption of solar heat can be improved significantly with absorbent coatings in the correct position. Also the real life situation of most homeowners. Just one inaccuracy, quadruple glazing units are not heavy when compared to other building materials currently used on the outside walls of a house. I know that the only times I notice the windows in my house is when it is cold or when there is too much heat from the sun, the latter is easily dealt with, I just open a window. The former is expensive to solve and involves me spending much more money on increasily expensive energy.
I was interested in triple glazing because our bedroom window faces North and during the winter we suffer from condensation most days. Do you have any suggestions?
Would everyone agree that skylights should be triple glazed? As I'm just deciding on this.. Thanks, Jeremy
A cheap way to convert to triple glazing is to apply shrink film insulation to double glazing. About £7 for 6SQM including tape to hold it to frame. It's only temporary but may last a few years if careful with it. E.g. Stormguard window insulation kit from b&q
Interesting and informative. Perhaps the way forward is to re-visit traditional shutters maybe constructed on a foam sandwich basis? Properly engineered and fitted they could offer a lightweight and efficient third barrier to heat transmission. Anyone tried it?
There's currently a lot of talk in the mainstream window industry trade press about triple glazing. At the moment, only around 1% of UK windows manufactured are triple glazed. But, I believe that this will increase steadily over the coming years. Our company recently went through a carbon footprint audit undertaken by SW Consulting and found that the carbon payback from installing upvc triple glazed windows, in place of double glazed ones with a U Value of 2.8 was less than three years. This is taking into account the embodied energy of of manufacture and installation, and comparing with the energy saving. The prices are coming down as more companies develop better systems, particularly in the uPVC sector. We've recently launched a website specifically for triple glazed windows: www.tripleglazingsuperheroes.com. Clearly, there's a bit of humour but the serious message is triple glazed windows are far superior to double glazed for energy saving and money saving. And there's more comfort, better security, less noise and so on. The German market with a similar climate has 40% windows fitted as triple glazed. Expect the UK market to develop this way over the coming years.
Triple glazed windows will result in a warmer bedroom and because of the argon gas in the triple glazed window, the pane that is facing inside wont get as cold and therefor moisture in the air wont condensate there as much. So yes it will solve the problem. If you have a a lot of condensation this could be down to poor ventilation. If this were the case then that would be a separate issue that would need to be addressed.
This may be a little late but I have just seen the question and the response may well help others. If good double glazing is fitted towards the exterior of the opening, well sealed secondary glazing flush with the inner wall surface can provide an extremely efficient solution. This is more or less the system used in Finland for decades (before triple glazing etc) When renovating a less than airtight Edwardian house with ornate multiple arches in the window frames I first restored the sashes retaining the beautiful float glass and then fitted Anglian secondary glazing (vertically sliding) with frames that did not obstruct the original frames. Now, in the coldest of winters I can sit in my bay window with curtains open and not feel any difference in temperature from other seats adjacent to radiators. The gap between old an new glazing is around 3". That arrangement was fitted in 1986 and still operates perfectly.
heh heh We have had a triple glazing for a century - come to visit Finland (or Sweden, Norway) .... ;-))
We have just moved into a new apartment, with all the latest Hi Tech equipment installed, however now that winter is nigh we are finding a serious problem with Condensation on every window in the place. can you tell me if triple glazing will make any difference or is this just another problem to be lived with ? FF.
We have both double and triple glazing installed in our house, we also have made use of secondary glazing units in our bedroom which gets no sunshine in winter. The secondary units which are installed 3inch from the double glazed units give better insulation than the triple glazed units in our garden room. suggest trying this befor the expense of triple glazing.
this will have at least 2 large fold away patio type doors to lead to 2different patio areas should these be triple glazed,obiviously i will have to getquotes but give me a ballpark figure for triple glazing the whole house (approx 2000sq ft)as compared with double glazing, iknow there will be hugh variations but that does not matter it will still give me a figure to work with
if you dont wish to go to the expence of a triple glazed window for your bedroom, a cheap alternative would be the diy option whereby you can buy kits of thick transparent sheets of plastic that come with an adhesive strip that you fit around the frames, the plastic sheet is then cut to size and attached to the adhesive strips, then a hairdryer is used to smooth ans seal the plastic sheets. as this is only for the bedroom and can be removed at anytime ,it seems like a cheap practical alternative. i believe these kits can be bought at good diy outlets like b&q hope this is helpful.
Triple glazing will certainly help this, however it is imperative that the glazing spacers are insulated. Also it is helpful that the window you choose has some sort of internal gasket otherwise any condensation will run down the face of the window and be absorbed by the glazing tape that protects the glass from shocks when the window is shut. If this absorbes moisture from condensation it can lead to the sash rotting! Antony Livingwood Windows LtdbatA6d
If the triple glazing is passive house certified by the passive house institute then it will help! Condensation results from warm air containing moisture, meeting a cold surface like a window. The moisture condenses from vapour to liquid. High quality triple glazing (or quadruple glazing) with U-Values as low as 0.5, will prevent heat transfer through your glass which means that your glass will actually be warm on the inner most pane and thus you wont get condensation! Although many manufacturers produce triple glazed windows, the best are the ones that have been certified by the Passive house institute such as these: Triple glazed windows Any triple glazing will help reduce condensation but certified windows are the best. Here is a thermal image of how these windows prevent heat loss: Energy Efficient Windows
George interesting comment about secondary glazing, can you tell me what ysstem you installed, how far from the window you installed it and how it has worked out at this stage? thanks Michael
we have a house on a busy main road and with triple glazing and in my opinion yes, the road noise is definately much reduced and our heating costs are also very cheap - this might also be due to other wall and roofing insulation options as well as the fact that its a stable conversion with thick walls and terraced. I do think however that the triple glazing also adds to the cost savings. we are in the south west of england btw.
To reduce your noise you need to install sound absorption glass as one of the panels to your new double or triple glazed unit, there are various thicknesses you can use. Unfortunately you have shutters which limits you to doing this - without the shutters you could have installed a sound absorption secondary glazed unit. Sound absorption glass works best with a large gap in between panels. Have a look at http://www.pilkington.com/cmsapplications/soundsimulator/simulator.html
Would like to get your ideas on retrofitting triple glazing on north facing block walls. Thanks
Hi i have just bought a 18th century cottage and need new windows, as A i am a very cold person and really feel the cold especially as our winters in England are getting worse, I would really appreciate the feedback as its just mind field buying new energy saving windows and doors, as I have downsized after my son and daughter have now left home. Budget really tight but this feel i need to make the best choice for my new cottage in the long term. Thanks much appreciated.
Hello Daniel Like you i have alot of road noise and heat loss through my existing double glazing windows. I have considered secondary windows. Would you mind giving me your views and anyother relevant information that would be of assistance. Noise is my biggest issue.Thank you for your help regards Michael
So -----noise an issue also!!!!!!!!!!!
Just replaced a 10 year old double glazed conservatory (which is open to the house)witha fully triple glazed 0.8 U value one. The difference is massive, we now have a lovely warm room with no cold spots. -8c outside and 20c inside, the roof was covered in frost which shows how good the insulation is. The conservatory is easily 5c warmer in cold weather and significantly quieter. It wasn't cheap (£10k) but the whole house is now warm and I am sure heating bills will be lower.
I have had a look at sureglaze.co.uk after reading your comment, by the looks of it they sell quite a premium product and a 0.7 is extremely energy efficient when it comes to u values. A double glazed A rated window is around 1.3-1.5 so if they are offering a 0.7-0.8 in triple glazing at a good price then I would say it is definitely worth it. Their website say's they are currently giving triple glazing for the price of double glazing so if you’re looking to buy it would be a good time. They are a national company so I don’t think your location would matter, I would get them out to quote and what the product and service is like. I think there are some other triple glazing companies also doing windows with u values of 0.8 but Sureglaze looks good.
Or, you know, curtains.
In 2005 I had the Internorm Edition 4 windows fitted in my flat in Edinburgh - it was cheaper to get these alu-timber windows imported from Austria than any of the local alternatives. The windows have double glazing towards the inside and an extra pane of glass towards the outside. A venetian blind is fitted into the gap. Significant noise reduction over double-glazed units AND ideal for bay windows where fitting curtains can be difficult. The latest Internorm windows achieve an U-value of 0.68.

I have been thinking of Triple glazing for a long time and there are many confusions out there, after a days worth of research it all depends of the glass specification. After calling my local building regs and a local company in Bradford called Glass Tec Windows, I decided to go for a 40mm triple glazed unit with a u-value of 0.6 consisting of planitherm total Plus with deceuninck upvc frames. after the installation triple glazing is worth every penny and I have seen savings already. For more information on my spec please visit www.glasstecwindows.co.uk

"Interesting and informative. Perhaps the way forward is to re-visit traditional shutters maybe constructed on a foam sandwich basis? Properly engineered and fitted they could offer a lightweight and efficient third barrier to heat transmission. Anyone tried it?"
Second this sentiment- shutters can be a benefit on either double or triple glazing. There's plenty of information over the net (Dr Paul Baker) shutters can come out with about a 55% reduction in heatloss through the window.
I'd be more than happy to drop the the shutters on a cold and wet December afternoon/evening in order to stay snug.

I installed triple glazing in my house in 1985/86. I was told I was mad at the time for paying the 10% extra it cost over double glazing. The only windows I get condensation on are my patio doors, which are double glazed, as I could not get them triple glazed at the time.
If quadruple glazing had been available in 1985, I would not have thought twice about paying the extra it would have cost, just for the improved level of comfort, even if people told me I was even madder.
I was also told I mad for putting 150mm of insulation in my outside walls.

Interesting, thanks. No-one's mentioned the ethical problems of uPVC - see here for more info: http://www.redbricks.org/home/gtr/why-we-do-not-want-upvc-windows/

Pity about what appears to be (Sureglaze) sales reps in disguise; give it a rest guys.