triple glazing

ahw23

We are about to replace two large 1969 aluminium double-glazed windows which have awful condensation issues. As these need doing anyway, we were going to go for maximum efficiency and get them triple-glazed, and were on the verge of going with Anglian. However, a few days into our cooling-off period, I have got cold feet and realised that other companies do actually have better u-values and potentially better prices. We're now looking into cancelling and are waiting from a ballpark figure from a local company who stock "Choices" brand (including passivhaus rated ones).

Does anyone here have recommendations or experiences with triple-glazing? Thanks!

Martyn1981

Hiya, there's a short thread with a few comments

Double and triple glazing

I'm getting some large conservatory windows replaced, and opted for DG as the TG was twice the price.

I've heard, but don't know if it's true, that for south(ish) facing windows DG is better as the solar gain is greater than the reduced losses.

No idea if that's true, but I have heard it a few times in various places. However, if you had the choice (were building a house or extension) you would go for small TG for north(ish) facing rooms.

If you do research this and find any decent info, could you post and let me know.

[Edit: I've found a chat thread on Navitron which raises a couple more issues, UK location - further north might support TG, and also using TG to reduce heat gain from south facing windows in the summer (if you get too much). M.]

[Edit 2: Got curious and have found most of the info here

Does Triple Glazing Make Sense?

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.

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.

ahw23

Hi Martyn! Getting a bit sidetracked, but you might like to know that we got approval from the DNO in the end for our 6.5kw pv. Now we just need to work out why the "fault" light is lit up on the inverter...

I believe that if you do keep all other factors constant, it is possible that over the course of a year, dg will be more energy efficient than tg. This is why the A+/A++ ratings etc. are based on both thermal transmittance and solar factor, and you can find A+ double glazing when some triple is only A. An "A" rating, if I remember correctly, balances gain and loss over the course of a year. A+ gains more than it loses. Just looking at Anglian promo brochures, the A++ triple glazing has 0.9 thermal transmittance compared with 1.4 in the A+ dg, BUT the solar factor is only 0.42, against 0.48. That will be more extreme in some brands as Anglian adjust the glass composition in the triple to limit the restriction of sunshine entering.

However, the crucial issue here is the timing of the solar gain, which for many windows is mostly in the summer: it's small comfort to know in the depths of winter that your lack of insulation will be compensated for by greater solar gain at midsummer. I'd love to know what the balance actually is in spring and autumn! The ultimate answer would probably be a well-designed passive-solar house with south-facing windows (triple but with low-iron glass) that are under overhanging eaves to limit sun when it's high in the sky but maximise it when low. Not many of those around, though!

Concerned75

I had triple glazing in my first house because of the trains. Didn't work a jot, but most of the noise was during the day, while I was at work.

ahw23

PS, for what it's worth, the windows in question are ESE, master bedroom and sitting room. The downstairs one is, hopefully, going to have a masonry stove in someday, so we really want to avoid the heat going straight through the wall before it has a chance to warm the rest of the house. I absolutely understand the point about money sometimes having more impact spent elsewhere, and payback times for windows being dreadful, but we have to change these anyway whereas various more cost-efficient measures (underfloor or internal/external wall insulation )aren't practical for this house at this time. So if we're going to do it, we'd rather do it well.

Exiled_Tyke

Last year I changed two large aluminium patio doors. TG wasn't even an option given they are 2.4m and 3m wide. In the end I went with a local firm (I'm pretty sure I read that Which? readers report great satisfaction with local providers than the big names). I got a better price than the big firms and better performing windows (sorry can't remember the details). A year later on the difference still amazes me, particular how warm the inside of the glass feels and yet there will be condensation on the outside on cold damp mornings. The windows are W facing. Leads me to believe that a good quality DG solution is good enough and probably far more cost effective than TG unless the circumstances are exceptional.

Martyn1981

ahw23 wrote: »

However, the crucial issue here is the timing of the solar gain, which for many windows is mostly in the summer: it's small comfort to know in the depths of winter that your lack of insulation will be compensated for by greater solar gain at midsummer. I'd love to know what the balance actually is in spring and autumn! The ultimate answer would probably be a well-designed passive-solar house with south-facing windows (triple but with low-iron glass) that are under overhanging eaves to limit sun when it's high in the sky but maximise it when low. Not many of those around, though!

Apologies ..... total face-palm moment! I just remembered more about my conversation and decision for going for DG (not TG) on our ESE conservatory glass (planned for late Feb) ........ BLINDS!

We have a blackout blind on our ESE Velux and it works perfectly. Silver reflective on the outside, and when closed you really can't see anything till your eyes adjust.

When I brought up the TG issue with the window man (who we've used many times before, and trust) he pointed out that flush fit blinds are much cheaper than the extra cost of TG. So we could block out almost all sunlight in the summer when it's too strong and hot, but let in more in the winter (than TG) when we want it.

That's our plan, and crucial to my earlier advice ..... how stupid to omit it. Sorry!

It's also crucial to our plan to fit an A/C unit in the conservatory, to feed through into the living room, as I wouldn't morally let my excess PV fight with nature (too much solar gain in the summer for AC, and too much heat loss in the winter for ASHP).