This small investigation performed in 2008 analyzes various glazing types as to their performance in energetic, cost and quality areas. It focuses on the following three questions

The energetic performance of glass types (does triple glazing reduce required heating energy?)
The environmental impact (are the extra energy and material for fabrication less than its savings?)
Cost (is it financially beneficial to invest in triple glazing?)

http://www.except.nl/en/#.en.articles.194-energy-and-cost-analysis-double-and-trip

Yes , that was it , full pdf on your link.

I would say, "yes always use 3g"

Now in Central Europe 3g is far and away the majority product

We in the UK are way behind. Double glazing salesmen and companies have us all hoodwinked

Assuming that someone is doing new windows then for me in a building 3g every time, not sheds or garages though.

Posted By: Gotanewlife
In fact isn't it the case that 3G, over 2G, is well worth it only after you have done everything else

Indeed, glazing in general gives very poor carbon reduction value for money. In my case even 2G comes in at about £10 per kg CO₂e per year compared to the existing single glazing, whereas most insulation jobs yield about £1-3 per kg CO₂e per year, and even a new boiler would only be £4 per kg CO₂e per year.

Glazing seems like it should be high on the priority list, but in reality if you're in a position where you're prioritising works, you may be better off keeping the bad windows and throwing your money at more effective measures. Windows are simply overpriced from a thermal efficiency perspective.

Just read the report and it does not exactly sing 3G (over extra wall insulation and 2G) praises in terms of ROI, CO2 reduction or even energy saving in south facing aspects - also mentions a indicative cost of 45 Euros/m^2 for 2G and 125Euros/m^2 for 3G. Perhaps things have markedly changed since 2008.......

In UK most fit UPVC 2G, 3G unit for same frames are around 15-20% more expensive. these are not all singing and dance top spec. expensive 3G but still claim Uw 0.8

Posted By: Gotanewlife
But the OP, Tony and I are really on about given you ARE replacing windows, is 3G worth the extra money over 2G?

The OP didn't really specify, and the paper they linked to was comparing the value of glazing to other forms of insulation. As they point out, you may come out ahead saving your money on 3G and spending the difference on wall insulation. It's worth taking a whole-house approach, rather than just focussing on the windows and their performance IMO.

Besides, when asking if paying extra for 3G is worth it from a purely financial point of view I think the overall poor cost-efficiency of glazing is relevant. Glazing is a bit of a necessary evil from a thermal cost effectiveness standpoint.

Which is insane, all it should cost is an extra sheet of glass and some spacers assuming decent quality frames.

Posted By: owlmanSo, not just a matter of sticking three panes into standard frames.

It seems that most of the uPVC window systems can do just that, just by using a narrower glazing bead - no re-tooling etc. Some only go to 36mm, but others can squeeze in 44mm 3G glass. Shame is the average window supplier is asked for it so rarely they don't know much about it. There is no reason why we shouldn't get 3G for just the cost of the extra (toughened) glass.

However if you want better insulated frame too then the costs really stack up. One day, I hope, it will be standard, for now there is a huge premium on a better frame because most people are content with the current kind and the extrusion manufactures sell miles of the stuff so se no reason to re-tool.

So cost effectiveness depends on how much glass in relationship to frame - big windows definitely go 3G (but chase a good price).

For me, it always boils down to getting 'the best bang for my buck'. I could install 200mm of internal insulation instead of 100mm but the first 100mm will do most of the work. Plus, in paying for all that insulation I might not be able to afford to upgrade my single pane windows, or afford to insulate the loft.

Tom the labour is the about same to put in windows (2G or 3G)and put in the 100mm or 200mm insulation! It costs extra for the 3G and whether that extra is best spent on the extra pane or extra insulation, etc is I think the question - except the the Triassic (the OP) is not here to say what he was getting at! If you have to do your windows because they have had it and the loft insulation is well past it you might well have the choice of 2G and loft insulation or 3G and no loft insulation - for example. I just think saying 3G is 'always best' VFM (ie the the OP's Q) is an unjustified generalization.

Posted By: fostertom3G cost negligible extra over 2G.

Hard to understand why 2G is not universally defunct then.

I can't comment on their motivation for saying so but a local window manufacturer told me that some of their windows can be A rated when double glazed and B rated when triple glazed. They said it's because triple glazing can reduce the amount of light that passes through and solar gain compared to double glazing.

The particular windows I was looking at from them could only accept 28mm units so I accept in this case the cost of adding the third pane may not be worth the expense. By using krypton fill the whole window u value for 3G was 1.0 opposed to 1.4 in 2G with argon fill.

Whether true or not I have been told that it is likely the krypton will have leaked after 10 years reducing the performance to less than the 2G window. I believe they are claiming that argon is less likely to escape but I have no idea how accurate these statements may be.

Far from my expectation (given the reputation double glazing salespeople get), not one window supplier has got back to me with a quote out of all the companies I have contacted in the last 3 weeks! Owing to this fact I am therefore not in a position to comment on the relative value of 2G vs 3G lol!

Posted By: slidersx200some of their windows can be A rated when double glazed and B rated when triple glazed. They said it's because triple glazing can reduce the amount of light that passes through and solar gain compared to double glazing.

That is the most outrageous bad-science sales puff that is actually enshrined in UK window-replacement governance.

The idea that when there's conditions such that there's solar gain, a 2G window will admit more gain than a 3G - that's true. However, they take the whole year incl summer for that calc - but in summer the last thing you want is solar gain. They should limit the calc to the heating season.

And another thing - the window has to be so placed that it actually sees the sun. Most often, non-south orientations and/or high horizons, whether terrain or nearby trees/buildings, block much or all of any solar gain during the low-sun heating season.

It's a racket, designed to justify/sell 2G against 3G.