Windows conundrum – living with triple glazing

[Simon R]

We are facing the dreaded windows selection conundrum and are trying to be objective, which is proving far harder than I would have expected.

 

We have a glazing element that includes a roof area for which we need curtain wall glazing. However it's only available in double glazing and has a U value of 1.5. It fits well aesthetically with the Velfac windows we are planning of using for all the other glazing. The company (Rhino) who supply the curtain glazing also do windows and were keen to quote. Now comes the big but...they can only provide double glazing and the U values are on the average 0.6 worse than the Velfac triple glazed windows. This is mainly due to them using aluminium frames while the Velfac are aluminium clad wood. The price delta between the the two quotes is considerable, indeed it is enough to pretty much cover our PV installation.

 

Looking at it from an energy value point of view using the standard HDD figure of 15 it's going to take a very long time for the additional energy required for heating to make up for the additional cost of triple glazing (about 30 years at current energy costs).

 

Given we are very happy with the build quality and look of both products it comes down to comfort.

 

Some thoughts on the experience of living with double glazing with U 1.5 and triple glazing with a U 0.9 would be very welcome.

 

Simon

[Declan52]

The major difference I notice is sound. I live beside a fairly busy road so triple glazed units where a must. 

How much outside noise are you likely to experience???

If noise isn't an issue I would go double and put pv in. The excess from pv generation is enough to heat my water for close on 6 months each year. What I generate covers all my electric bills so having pv is well worth the sacrifice.

[gravelld]

I don't have any personal experience.

 

However from my reading it appears the main benefit of 3G is that of comfort derived from:

 

- Lower radiative losses which particularly matter when standing close to the window

- Lower down draughts from the glazing (the Ph minimum Uw for windows is based on this I believe)

 

Pertinently, both of those points could have a big effect on curtain wall glazing, such is its expanse.

 

As I say, no personal experience.

[Triassic]

In a highly insulated home we found double glazing suffered from condensation. You might find the roof glazing drips on you !

[PeterW]

Personal experience of 3G in UPVC is noise and the lack of a “cold” feel near the glass. Very surprised how much heat they retain, downside is that you do lose a lot of the solar gain so they have a mix of benefits. 

[Simon R]

59 minutes ago, Triassic said:

In a highly insulated home we found double glazing suffered from condensation. You might find the roof glazing drips on you !

We get that problem on the boat! yes we will be highly insulated, I had hoped that having an MVHR would alleviate that problem. How much of a problem do you find it and are you running an MVHR system.

[Simon R]

1 hour ago, Declan52 said:

The major difference I notice is sound. I live beside a fairly busy road so triple glazed units where a must. 

How much outside noise are you likely to experience??? 

If noise isn't an issue I would go double and put pv in. The excess from pv generation is enough to heat my water for close on 6 months each year. What I generate covers all my electric bills so having pv is well worth the sacrifice.

Thanks. No sound issues, a very quiet location. So I'll chalk that up as a vote for double...confirmation bias creeping in already...?

[joe90]

I also live in a quiet location and my double glazing is within a gnats whisker of triple. I want the solar gain and plan to have heavy curtains when it’s dark and cold outside.

[PeterW]

22 minutes ago, Simon R said:

Thanks. No sound issues, a very quiet location. So I'll chalk that up as a vote for double...confirmation bias creeping in already...?

 

My triple was cheaper than others double and better performance ...... reset the balance ...?

[Simon R]

11 minutes ago, joe90 said:

I also live in a quiet location and my double glazing is within a gnats whisker of triple. I want the solar gain and plan to have heavy curtains when it’s dark and cold outside.

Another vote for double. What sort of U values did you achieve, just concerned that the aluminium frames may be a problem.

[joe90]

1 minute ago, Simon R said:

Another vote for double. What sort of U values did you achieve, just concerned that the aluminium frames may be a problem.

 

I don’t have the figures to hand, my frames were hand made in oak, very “cottage”, if they were triple the frames would have looked very chunky.

[the_r_sole]

.

Edited September 26, 2019 by the_r_sole

[Simon R]

1 hour ago, PeterW said:

 

My triple was cheaper than others double and better performance ...... reset the balance ...? 

Ah, that would be perfect, just not an option from our chosen suppliers....perhaps I should re-open that can of worms and look for yet other suppliers.

 

[PeterW]

Don't discount UPVC for performance and looks. You can get Rehau and others in a fair number of colours and they are very good - I considered anthracite recently but only dropped it as the fascia supplier and window supplier had slightly different colour samples.

 

 

[mike2016]

Hi,

I went out to a showroom to have a look at the Velfac. Have you seen an example? They didn't have a triple glazed option in store I'll be up front. When I opened the top hung model they had, the opening section is all aluminium with the glass in it, no wood. The wooden frame is the fixed part and has no outer Aluminium. It's the wierdest thing, get a look at one if you can. Maybe it wasn't the same range you are getting, I hope not! 

[Triassic]

Have you considered thermally broken aluminium farames?

 

https://goo.gl/images/fTPGDG

Edited September 26, 2018 by Triassic

[Dreadnaught]

Keep in mind that the window frame has a much lower u-value than the glass, whether 2G or 3G, and the frame can represent a surprisingly large proportion of the total face. 

 

Perhaps focus less on 2G v 3G but look closely at the frames.

[Simon R]

14 hours ago, Triassic said:

Have you considered thermally broken aluminium farames?

 

https://goo.gl/images/fTPGDG

The Rhino frames are thermally broken but even so are pretty poor in terms of U value, the profile is U2.9 which is OK on the larger windows but not so good as the ration of glass to frame diminishes. The profile supplier is AluK, very nice high quality product range. We are also going to look at Reynaer which look almost identical  to the Aluk product but have a larger thermal break and will take triple glazed.

 

17 hours ago, the_r_sole said:

have you looked at senior architectural glazing? they do a hybrid curtain wall system which has timber frames and will take glass up to 28mm

Not a firm we had come across, so thanks I'll take a look.

 

15 hours ago, PeterW said:

Don't discount UPVC for performance and looks. You can get Rehau and others in a fair number of colours and they are very good - I considered anthracite recently but only dropped it as the fascia supplier and window supplier had slightly different colour samples.

 

 

We did look at UPVC but found the frames rather bulky and we are trying get as low profile as we can. UPVC does represent the best performance value of any windows we have looked at though.

[mvincentd]

Aluminium frames with PUR insulated cores that pass all the CWCT tests, and provide unified profiles with all your other windows, at Velfac prices; idealcombi Futura. 

[le-cerveau]

Internorm (expensive) do large scale glazing PANORAMA HX300 which can be integrated into the building.