Replace window glass vs new windows

b.gud

Hey folks I'm looking for some opinions/advice on replacing all our windows vs just replacing the glass.

We are currently doing some big renovations on our house including a new extension, replacing doors, insulation (attic and pumping walls), and a new gas boiler. We also want to upgrade our window and need to choose between just replacing glass or replacing glass and getting all new windows. When all the works are done I want to make sure that the house is very efficient both in terms of heat loss and energy usage but also want to ensure that we are using the budget as wisely as possible.

With that in mind I have gotten quotes for full new windows and replacing just the glass and now need to decide between them. For the new windows they would be from Munster joinery fully passive triple glazed with a uValue of 0.7 and cost of approx €8000. The replacement of glass would be from vista therm and have a uValue "as low as" 1.0 and would cost €3000.

Essentially I'm trying to decide if it is worth the extra €5000 for the new passive frames or is that money better spent else where.

buzzerxx

https://www.boards.ie/discussion/2058338551/replace-window-glass-vs-new-windows

Triple glazing needs to be between 36mm to 44mm to be any good for thermal qualities. Your old windows more than likely have beading for 28mm double glazing. Triple glaze units can be made at 28mm thick ( 4-8-4-8-4mm) but thicker than 8mm gaps between glass would be better, therefore new windows would be best.

b.gud

https://www.boards.ie/discussion/comment/121838126#Comment_121838126

Thanks very much for taking the time to reply. I know that triple glazed will be better I suppose the main thing I'm wondering is it worth spending the extra 5K vs the new double glazed with a uValue of ~1.0

listermint

https://www.boards.ie/discussion/comment/121838230#Comment_121838230

No it's not, not unless you really require it's sound deadening benefits. If yes then yes. If sound isn't a major factor the u value difference is negligible.

Plus the extra weight of them means the hinges are more susceptible to earlier slippage meaning movement meaning the gaskets can get gapped sooner than a lighter window.

Food for thought.

b.gud

https://www.boards.ie/discussion/comment/121838239#Comment_121838239

Thanks very much for the reply. I was thinking that the uValue difference probably wasn't much but wanted to get some other opinions.

Sounds deadening isn't our major concern but out of curiosity what kind of sound deadening differences are you talking about between double and triple glazed?

buzzerxx

Listermints comments are true, especially about the weight factor but I am 38 years in the window business and this is a new one to me -

Is triple glazing more soundproof than double glazing?

''Yes and no. When compared to standard double glazing, triple glazing can reduce noise by simply placing another barrier in the way of the noise. However, as standard triple glazing is not designed to combat noise, it can actually make things worse. You see, two air gaps can create resonance and echo chambers.''

So now i am unsure about recommending triple glaze over double glazing for better sound blocking

listermint

https://www.boards.ie/discussion/comment/121838330#Comment_121838330

Fair!

Mellor

https://www.boards.ie/discussion/2058338551/replace-window-glass-vs-new-windows

What do they mean by passive triple glazed? Be wary of marketing labels, stick with performance.

Would want to know what the overall u-value would be not just “as-low-as” for the glass only replacement.

Lumen

https://www.boards.ie/discussion/comment/121838330#Comment_121838330

My understanding is that this can be improved by specifying different widths for the two gaps. The issue is that particular frequencies of noise can propagate across a given gap, so by using two different gap widths you block those frequencies, a bit like when you put one set of polarised sunglasses in front of another, rotated at 90 degrees, and all the light is blocked.

A big part of sound proofing is mass, so there's no real getting away from high performance windows being heavier, except by clever design, e.g. breaking up large fixed panes, or having gravity work with the hinges (e.g. using top hung windows).

Mellor

https://www.boards.ie/discussion/comment/121840707#Comment_121840707

Different air gaps make little to no difference. All frequencies/waves will still cross either gap. What you’re thinking of is varying the thicknesses of glass itself. If the thicknesses are the same, the panes can resonate with each other. Eg 6+10mm is better than 8+8mm.

In general the cavity range found in IGUs (6-16mm) makes little difference to acoustic insulation. Acoustic partition will typically be in 60-100mm.

Lumen

https://www.boards.ie/discussion/comment/121840988#Comment_121840988

Thanks for the correction! Total brain fart there.

MicktheMan

Essentially I'm trying to decide if it is worth the extra €5000 for the new passive frames or is that money better spent else where.

Imo and experience the extra €5k is well worth it for the passive certified units (assuming of course that the windows are installed airtight). The difference in comfort is notable.

Whether the €5k could be better spent elsewhere question isn't really possible to be answered with the info supplied. For instance, have you had an air tight test done on the house before the renovation plan was drawn up? If so, what was the result and the top 4 issues found? Have you sought independent advice from a heat loss expert?

Mellor

https://www.boards.ie/discussion/comment/121842468#Comment_121842468

No worries. Sound make very little sense at times. Behaves somewhere between water and black magic

b.gud

https://www.boards.ie/discussion/comment/121842866#Comment_121842866

Thanks very much for the reply. We didn't get an airtightness test done but did get a BER our current windows are rated at a uValue of 2.8 so both will be a big upgrade

MacDanger

I would have thought that the big advantage of getting new windows installed in a situation like this would be the draught-proofing around the new windows compared to what's there in the existing?

b.gud

https://www.boards.ie/discussion/comment/121848252#Comment_121848252

That would definitely be my main reason behind going with the new windows, but the frames aren't too old so if just replacing the glass and some routine maintenance of the existing frames was going to give me a good boost in efficiency then I was thinking it might be a good idea and we could save the 5k to spend elsewhere

Mellor

https://www.boards.ie/discussion/comment/121848252#Comment_121848252

The benefit of that depends on airtight the rest of the house is

K_F

Hi, just wondering which decision was made or if a glass only replacement made much of a difference? thanks

b.gud

So I ended up just replacing the glass. It's kind of hard to say how much difference it's made because we've also had a lot of other works done, like an extension, extra insulation and new doors. Plus since the works are just finishing now and the weather has been crazy mild we haven't really gotten a sense of the differences of much of it yet