How much of a difference does 3g make over 2g?

[Juj]

Is 3g worth the investment over 2g?

 

We have a lot of windows and doors, including sliders etc, altogether we're looking at 200m2 over 70 items.  I've had around 10 quotes now and the feedback from the window companies has been to stick with 2g (possibly because they know it's cheaper and therefore within my budget) however, it seems the majority of you guys have 3g and you all seem to know what you're doing! 

 

I would say that my main priorities are equally:

 

Quality (highly rated, long warranty etc)

Aesthetics (They have to suit the contemporary style of the house, the slimmer the better)

Cost (I'm trying to get a LOT of house for the money so would be glad to just get the shell made, sealed and clad leaving the rest to be finished bit by bit)

 

I've had quotes from all the main players mentioned on here selling Alu clad as well as some Aluminium frame companies and there are many pro's and cons with each.  Initially I was pretty set on 3g but I simply can't ignore the potential additional cost, it could be the difference between getting the project started right away or waiting a while longer to save up the necessary funds.  I'm even considering flush casement plastic windows as they look pretty decent but I'm yet to be convinced.  

 

Ultimately, this is our forever home and as such, I really don't want to make a decision I'll later regret.

 

P.S - We're not building a passive house but it will be as air tight as we can make it (ICF construction married to brick and block)

 

 

[CC45]

We put 2g in, the cost saving will pay for years worth of gas.  We've spent the saving on other energy saving extra's - eg MVHR.

 

Your decision may be influenced by sound insulation and reduced window drafts - 3g better than 2g here.

 

All the decision making is a killer.

[PeterW]

I’ve used 3G uPVC and the noise difference is fantastic. Also the solar gain is less which is important with 2 set of French doors facing south east and the rest of the windows facing south. 

 

That sounds a huge amount of glazing though - is it worth a design change to reduce it ..?

[Thedreamer]

I couldn't decide whether to go for 2g timber or 3g timber. As this is our forever home, I decided to go for 3g. As we went for 3g then it made sense to put in alum clad as well.

 

Windows arrived on Friday and went in today, really happy with them.

 

 

 

 

[Juj]

@CC45 Decisions, decisions!  Do you think you would do it the same way again? Our situation is that we can hold off as there is no great race to get things done other than wanting it done! We could potentially wait until finances are more favourable, could be years we're here for life so can wait if its something really important.  I'm just not sure if 3g is a game changer!

 

@PeterW Solar gain shouldn't be a huge problem as most of the major glazing is West facing, south facing windows are either shaded by hedges or have been minimised already.  Less solar gain would be a bonus, as would less noise but neither are enough to swing it, air tightness and insulation are probably bigger factors but how much heating would I save for the £££'s extra in outlay? Regards to scaling the glazing down, that has been scaled down! lol (it's a huge build for a large family!)

 

 

[mvincentd]

i'm of the belief that regarding sound there's little between 2 or 3g....its the distance between the panes that affect sound??

[nod]

We were restricted red by planning to Sash windows 

Never even considered triple glazing We purchased the best quality and design that we could find

Lots of other things we could spend our money on

Wibdows have been one of our largest experiences Even though I’ve fitted them all myself 

Just the bifolds to fit this Saturday morning 

[Ferdinand]

The best 2G is now not much different from some 3G in thermal values, and there are options around such as dark grey upvc (Eurocell amongst others) that look very sharp.

 

In my head I think of upvc 2G as a 25-30 year solution, and aluclad 3G as a 50 year solution. Not sure if that is a useful reflection for you ... and there are plenty on here who know far more than me about 3G.

 

It is quite possible that someone will take a quarter or a third off their price to get an order on the spot. But a8 am sure you know that.

 

We also see very significant price variations for things that are ostensibly very similar. This thread from Jan 2017 quotes 3G prices:

 

 

the range quotes for 3G is say £250-600 per sqm plus £70-100 per sqm for fitting, very very roughly, and with some outliers for special or idiosyncratic requirements. And you can get quote variations of 200-300% for a seemingly similar project or job. These are for jobs in the 25-100 sqm range mainly, so I would expect a price 7-15% less than otherwise for your 200sqm Crystal Palace (!) job. But this is just me guesstimating. Obvs there is a cost vs service trade off.

 

For 2G I would estimate perhaps 20-30% less than an equivalent 3G, but again that is gut feel.

 

Were I doing a new build, I would probably look for the high quality 2G or 3G established use product without going to the bleeding edge, and be willing to simplify my design in search of price (eg using a small range of window sizes or French Widows rather than a space-engineered nirvana). But that is just my general mindset, and others are just as valid.

 

Hope that helps.

 

Ferdinand

Edited July 24, 2018 by Ferdinand

[Ferdinand]

This is a useful chart from @Visti on the other thread about his quotes fro 48sqm.

 

Edited July 24, 2018 by Ferdinand
B B B Apple

[Jeremy Harris]

Worth remembering that the subjective effective of 3G in cold weather is that it is a great deal more effective than the best 2G.  The reason is that 3G can have two internal facing low e coated panes, whereas 2G can only have one.  The effect of this is to pretty much half the long wavelength IR heat loss through the windows, and although this doesn't make a massive difference to the overall thermal performance, it does make a massive subjective difference if you stand or sit next to any glazing on a cold day.

 

Our bodies sense comfort by lots of ways, but one is the rate of radiated heat loss.  When next to a 2G window more heat from our bodies will radiate out and it will feel cooler than it really is.  The IR loss through double low e 3G is so small that I can't tell if I'm in front of the glazing or not, as such a large amount of body radiated heat is reflected back.

[Dreadnaught]

9 hours ago, Juj said:

Solar gain shouldn't be a huge problem as most of the major glazing is West facing, south facing windows are either shaded by hedges or have been minimised already.  Less solar gain would be a bonus

 

Beware, west-facing windows can still be a problem for overheating because the sun is lower when it is in the West and so the sunlight penetrates more deeply into the thermal envelope. Westerly (early evening) sun is also more of a problem than easterly (morning) sun because by the evening the building is already hotter. (I learnt this by reading about shading affects for passive houses and modelling my own build in PHPP.)

 

On the subject of 3G vs 2G, for me its a philosophical decision of whether to adopt the principle of a fabric-first approach. Fabric-first prizes comfort above all, as does 3G.

Edited July 24, 2018 by Dreadnaught

[lizzie]

@Juj I agree with @Dreadnaught about the west facing aspect.  I have overheating problems and am currently trying to sort out a solution.  My South facing windows are not too bad, I could live with that but the West facing ones are a major problem, I didnt think they would be I thought south worse but no.  Look very carefully at the west....I have majority of my large glazed area on the west side?

[Jeremy Harris]

By far the worst for us are the East and West facing windows, as above, because of the low angle of the sun that allows greater room penetration.  For us East is worse than West, but that's because we're next to a stream and lakes, so in the afternoon the air is often a bit hazy, from water vapour in the bottom of the valley.  This seems to decrease the solar gain from the West a fair bit.

[Juj]

Thanks for the links @Ferdinand I'd already read most of what's on here and have pretty much applied the same assumptions you have regarding prices but it's a little hit and miss, I've only had a couple of particularly competitive quotes, the more popular ones (Rationel/ Internorm/ Idealcombi etc) that I'd expected better quotes from don't seem to have factored much of a quantity discount although I'm not at the order stage so perhaps they've built a fair amount of play into their quote?

 

Also, thanks for the heads up about the East and West facing windows @JSHarris, @lizzie & @Dreadnaught Perhaps a solar film will be in order to prevent excessive solar gain? I'm beginning to err towards a very good 2g as opposed to 3g, the cost savings will pretty much pay for a decent solar set up.

[lizzie]

@Juj part of me regrets I did not go for the Velfac windows. Lovely slim frames but only 2g. They assured me the u values would be Ok for my build but I was hooked on the holy grail of 3g and went for eye wateringly expensive Internorm LOL

[joe90]

Well I went for 2g, wooden frames made locally (cottage  style ), our bi folds are protected by a 2g conservatory so 4g ?. Our window supplier has a glass technician and with coatings got within a nats whisker of 3g in thermal value. Our conservatory is having solar glass in the roof to cut down overheating . Most of our windows are small to fit with the cottage theme.

[CC45]

I'd go 2g again - if money was not a consideration - aluclad 3g

 

Unlikely to last another 30 years on this planet so difficult to press the button when the price difference was £000's.

 

get a few quotes and then go from there.

[PeterW]

3 hours ago, CC45 said:

I'd go 2g again - if money was not a consideration - aluclad 3g

 

Unlikely to last another 30 years on this planet so difficult to press the button when the price difference was £000's.

 

get a few quotes and then go from there.

 

 

uPVC 2G vs 3G was a difference of about £450 all in - thats 4/12/4/12/4 from memory but 2 layers of lowE glass 

 

[Jeremy Harris]

Last year quite a few of the uPVC suppliers were offering 3G for the same price as 2G, so I think that, on a like-for-like quality basis there is probable very little difference in price.  Most of the cost in windows is in making the frames etc; the glazing unit isn't a massive cost element, so there really shouldn't be much of a price difference. 

[PeterW]

That was true @JSHarris when I was doing the specs - the difference only came in when I started to add the laminated or toughened glass and the other factor was the weight of the units affecting what the maximum openers were. 

[Ian]

12 minutes ago, JSHarris said:

Last year quite a few of the uPVC suppliers were offering 3G for the same price as 2G, so I think that, on a like-for-like quality basis there is probable very little difference in price.  Most of the cost in windows is in making the frames etc; the glazing unit isn't a massive cost element, so there really shouldn't be much of a price difference. 

+1

Our Rehau 3G windows cost about £500 more than 2G. (We had 18.5 sq.m of windows and french doors) The frame is the standard 70mm Rehau profile which can accept 44mm glazing units so 3G is typically 4-16-4-16-4 which is not far off the optimum spacing. Inner and middle panes Low E. All 3 panes toughened and low iron. Argon fill. Super Spacers.

Edited July 25, 2018 by Ian

[gravelld]

@Ian which Rehau system was that - Geneo, Total70?

[lizzie]

My Velfac 2g quote was 10k less than the Internorm 3g.............big difference 47sqm glass

[Jeremy Harris]

33 minutes ago, lizzie said:

My Velfac 2g quote was 10k less than the Internorm 3g.............big difference 47sqm glass

 

 

But the difference there is between brands, rather than glazing.  For example, our aluclad 3G from Munster (same finish and style inside and out as Internorm), was around £8.5k fitted and with cills.  From Internorm it would have cost over £23k fitted with cills.  Admittedly the Internorm internal finish is slightly better, but I can't see any difference in terms of the main frame extrusions or the handles and hinges.

 

In terms of performance, the Munster 3G windows are slightly better than the Internorm 3G ones, both had two low e internal panes.  Munster used Saint Gobain Planitherm Argon Gold glazing, not sure what Internorm would have used, but it had to be broadly similar.

 

As I said above, the prices differences aren't driven by whether the glazing is 2G or 3G, they are driven by other factors in the main.

[Ian]

1 hour ago, gravelld said:

@Ian which Rehau system was that - Geneo, Total70?

It was Total 70 in a charcoal grey colour

supply & install price was £4,800 for 18.5 sq.m including a front door so £259 per sq.m

 

Edit:

for anyone interested in Rehau for 3G windows here's their spec for the glass that you need to achieve 0.8 'U' value using their standard Total 70 frame system. (I used something similar from Pilkington for my own windows)

 

0.8_5 chamber.pdf

Edited July 25, 2018 by Ian