Changing from double to triple glazed, worth it?

naughtysmurf · 08-02-2025 01:54PM #1

Our house was built in 1997, 4 bed semi, gfch, newish boiler, it has doubled glazed upvc windows, the walls are pumped, attic well insulated, it is not a cold house, we have an inset stove too, is it worth changing them all to triple glazed or is there something better I could do with the money from an insulation perspective?

Thanks

10-10-20 · 08-02-2025 03:26PM

Hi, in my opinion the key is to gauge the existing double-glazing and establish what saving might be made by changing to triple. Do this by measuring the thickness of the units and estimating the gap. As you see from this site they reckon that older double units with a 12mm cavity may have a u-value of 2.8, while newer double units with a 20mm cavity may have a u-value of around 1.2 to 1.8. Then triple 34mm has a performance of 0.7.

https://asgardwindows.ie/windows/glazing-options

Then do the maths on the surface-area heatloss in kWh (here's a basic calculator):

https://nordan.co.uk/explore/energy-calculator

In my case I had low quality double glazed "contractor spec" windows fitted and they came with a host of issues around noise, leakage and thermal problems. I estimated that they were giving me a U of 2.8 or so, hence the move to triple was expensive for the gain of around 2.1u, it resolved all of the tertiary issues in one go.

Hope it gives some guidance.

MicktheMan · 08-02-2025 08:35PM

In our mild and windy climate, the holy grail in most houses is air tightness (or lack of) … so, imo, your first port of call is to find out what your level is and take it from there.

As an aside, there is a general myth out there that windows and doors are the cause of poor air tightness. This is rarely the case however with other issues normally coming to the fore depending on house type etc which is a eye-opener for the home owner.

MicktheMan · 08-02-2025 08:36PM

And most air tightness solutions are eminently diy'able.

10-10-20 · 08-02-2025 11:32PM

https://www.boards.ie/discussion/comment/123149423#Comment_123149423

Leakage from the cavity around the internal cill is the main issue. Easily fixed with air-tight tapes and patience.

CrazyEric · 08-02-2025 11:39PM

My double glazing is about 20 years old and a few panels are starting to go. I replaced the first one last year but there are 3 or 4 more this year, is it an option to just get the glass replaced? the frames are ok. My thinking is to just get every panel replaced in one go.

10-10-20 · 08-02-2025 11:48PM

https://www.boards.ie/discussion/comment/123149915#Comment_123149915

Yes you can do that, it's not uncommon if the frames and seals are in good condition. You just need to ask them to fit the latest low-e equivalent of your existing double glazing. It's normally a quick enough job once the glazing units are assembled.

CrazyEric · 08-02-2025 11:54PM

Same company that originally installed have all the measurements on file so I think it would be painless enough

Allinall · 09-02-2025 12:05AM

If it’s not a cold house, why do anything.

Enjoy your money.

phormium · 09-02-2025 12:18AM

https://www.boards.ie/discussion/comment/123149962#Comment_123149962

I had glass in 4 windows in front of house replaced this year, frames good enough (34 yrs old), I really only changed them because I was so sick of those georgian bars in them! Now they are plain and a big advantage totally scratch free compared to the originals that the plasterers ruined! It's also apparently a better quality warmer glass or something, that wasn't my motivation but they assured me it would make those rooms warmer, as it happens front of house faces north so no harm!

Took about 6 weeks from measuring up and fitted in a few hours, was very happy with it.

Grassy Knoll · 09-02-2025 12:35AM

if your windows are nearing replacement and the marginal cost for the better spec is reasonable, go for,it. We,did and certainly it has helped make the house cosier. We also had our BER done recently and hit a B2. The windows certainly helped.

whizbang · 09-02-2025 02:05AM

You would get far better bang for your buck with Heat pump. if its a no go, then spend the money on why its a no go.

10-10-20 · 09-02-2025 01:15PM

https://www.boards.ie/discussion/comment/123150194#Comment_123150194

You mean to just get a heatloss report done and then work from top-down. Makes sense.

MicktheMan · 09-02-2025 02:43PM

Leakage from the cavity around the internal cill is the main issue.

Not necessarily and we don't know enough about the house to give such a definite opinion.

In the majority of houses I test, this detail would be 3rd or 4th on the list if on the list at all. It would be rare enough for it to be the primary overall issue.

monseiur · 09-02-2025 09:41PM

https://www.boards.ie/discussion/comment/123150194#Comment_123150194

With a 1997 built house OP may need all his savings to pay his future electricity bills if he goes down the heat pump route.

ted1 · 09-02-2025 09:58PM

https://www.boards.ie/discussion/comment/123150194#Comment_123150194

I don’t believe you will.

naughtysmurf · 10-02-2025 08:59AM

Thanks for the response,

A heat loss test sounds like a good starting place anyway & address any issues that show up there, for the Mrs the windows are more of a cosmetic issue, scratches, odd handle requiring replacement etc

Not interested in rushing down the heat pump route at the moment as I don’t have enough knowledge on them, you do hear the horror high bills stories & don’t want to be reliant on one energy / heat source (see recent storm cases ) having said that my daughter has been renting for the last couple of years places that have heat pumps & the energy costs are very good (low) these are both new builds though, I’d want to make sure that my 1997 house was properly prepped before going down that route

It’s all food for thought though

Thanks

DC999 · 12-02-2025 04:37PM

https://www.boards.ie/discussion/comment/123149423#Comment_123149423

Mick, can I ask how air tightness problems are identified? The airblower test shows there are X air changes in the whole house. But how do you then find the issues per area / room?

Do you then seal off 1 room so it’s removed from the reading? Meaning you deduce the air changes from that room? And then rinse and repeat that?

My folks got 7 mins of an airblower test post external insulation. So you couldn’t use that to pinpoint what needs to get resolved. It just shows the overall air leakage. And that test wasn’t for that reason of course.

MicktheMan · 12-02-2025 07:03PM

https://www.boards.ie/discussion/comment/123163435#Comment_123163435

Very good question @DC999 and probably where some of the confusion comes from.

The official test will give a result which in itself is only useful for data entry into whatever piece of software / compliance program demands it. It is a relatively quick test and this is probably what your folks got.

The way I use the blower door (as part of an overall heat loss survey) is to, yes, determine the air tightness figure, and then the fun begins. I depressurise the house to -ve 50 Pa, allow the house to adjust and airflow patterns to emerge and then use my thermal imaging camera, smoke pen, my fingers, my common sense and experience to find the issues and to grade them according to their relative importance. I also insist the client is present so they can see & feel for themselves what's happening (very often to their utter amazement) and go through their options to address. This process takes hours (my average survey time would be 6 to 7 hours).

I do not give a specific figure for each room or indeed for any particular type of leak identified (no point), yet the client is left with a clear roadmap / plan of attack.

Hope this helps explain it a bit :)

Changing from double to triple glazed, worth it?

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