Triple Glazing & Seals

[neversay]

I'm upgrading two large 3-panel bay windows and one small bedroom window in a house that otherwise well insulated, not particularly noisy, and we're here for many years. The base price is £1817 all-in for good quality double glazed white-upvc from a good local manufacturer and one-man fitter. Asking about the triple glazed upgrade they say allow 40% extra cost on the units for a reduction in U value of 1.4 to 0.9. Given that a competing quote for comparison was £3.3k would others go for the triple glazed upgrade or pocket the saving?

Also, I read that it's all well upgrading the units but then some fitters use a sealant or expanding foam that undoes some of the benefit. Is there a recommended approach for doing a thermally efficient seal?

No need for hard analysis on the pros and cons of triple glazed as I know they have been discussed before. Just a quick thumbs up or down would help my sanity check as at present I'm swaying toward upgrading.

[jackdaww]

I'm upgrading two large 3-panel bay windows and one small bedroom window in a house that otherwise well insulated, not particularly noisy, and we're here for many years. The base price is £1817 all-in for good quality double glazed white-upvc from a good local manufacturer and one-man fitter. Asking about the triple glazed upgrade they say allow 40% extra cost on the units for a reduction in U value of 1.4 to 0.9. Given that a competing quote for comparison was £3.3k would others go for the triple glazed upgrade or pocket the saving?

Also, I read that it's all well upgrading the units but then some fitters use a sealant or expanding foam that undoes some of the benefit. Is there a recommended approach for doing a thermally efficient seal?

No need for hard analysis on the pros and cons of triple glazed as I know they have been discussed before. Just a quick thumbs up or down would help my sanity check as at present I'm swaying toward upgrading.

=========================

key advantages of multiple glazing are draught exclusion and noise insulation .

i very much doubt if going to triple would be significatly better , and may add to complexity amd maintenence .

we are delighted with our double.

[Maroochydore]

I've just renewed my front porch which had full height double-glazed panels. They were 22 years old.
We were going to upgrade to triple-glazed for better insulation but were advised by our supplier that with the increases in technology of the framing and especially the glass coatings that we really wouldn't gain any benefit.
We saved our money.

[dspp]

I have triple glazed on some large full height doors & windows in my kitchen. It means I can sit next to them in the middle of winter, and it is not at all chilly, i.e. it is just like being sat next to a inside wall. It also means that when the local helicopters land over my house it is no real bother (though that was something I only realised after the purchase event).

Whether this is worth it to you is a matter of judgement. For me it was, and I haven't regretted it. The costs look about correct by the way, as does the U-value benefit.

(Re the sealing issue, the modules are sealed when built as part of that U-value uplift. If you are re-using your existing surrounds/frames that aspect won't change. If new surrounds then simply specify a correspondingly good quality surround).

On TLF it is only possible to give a thumbs-up. So beware the distortion in the results .....

regards, dspp

[neversay]

Thanks all.

@dspp - yes, the price includes the new frames. I was just thinking of any sealant/filler between the frames and walls (although the fitter is very good).

FWIW the triple glazed for two large bays and one small bedroom window comes to £1955 excluding fitting. Sadly I don't have the double glazed quote without the fitting cost in order to accurately compare the two. It will still be well under the £3300 that the other company quoted for double glazed (spot the perceptual bias of anchoring here!).

[Dendyver]

On the question of double vs. triple glazing be careful not to lose the insulation benefit by what is inserted between the glazed unit frame and your wall. I do not know the answer to that one, but I am mentioning it because I have come across some dodgy infills.

Another scam which seems to be tolerated by Building Control is that for decades in England (UK?) where wooden windows were used in the original construction there were no lintels used above the wooden frames, the builders relying on the wooden window frames to support the external brickwork - even in blocks of flats!!!!!

You can see the problem when the wooden frames are whipped out subsequently and replaced by UPVC window frames. A minute sag of the external brickwork can lead to water penetration in driving rain.

[Slarti]

On the question of double vs. triple glazing be careful not to lose the insulation benefit by what is inserted between the glazed unit frame and your wall. I do not know the answer to that one, but I am mentioning it because I have come across some dodgy infills.

Another scam which seems to be tolerated by Building Control is that for decades in England (UK?) where wooden windows were used in the original construction there were no lintels used above the wooden frames, the builders relying on the wooden window frames to support the external brickwork - even in blocks of flats!!!!!

You can see the problem when the wooden frames are whipped out subsequently and replaced by UPVC window frames. A minute sag of the external brickwork can lead to water penetration in driving rain.

I had that when they were fitting the double glazed front door in my 50s built house.
Panicked cry from fitters who were removing the front door frame, only to find that there was noting holding in the "soldier" bricks above the door!
They knocked the door frame back and went and bought a metal lintel bar from Jewsons which they eased in above the door frame, somehow. At my expense, obviously.

All of the other windows and doors in the house were normal. Mind you, what was the back door in the kitchen is still the same frame, even though it now just leads to a utility room and has a different door in it.

It is not the minute sag that is the worrying thought, but collapse!

Slarti

[PrincessB]

Asking about the triple glazed upgrade they say allow 40% extra cost on the units for a reduction in U value of 1.4 to 0.9.

That sounds completely off.

It would sound to me that they know some people who make double glazed panels who are conservative about doing something they don't know how to do.

You're only after a third bit of glass in the sealed units, so where does 40% more come from? I seem to recall that the difference for largeish windows was more like £40 for triple over double on my last build. Bear in mind that the frames are the same, so the only difference is the sealed units which are fitted into the frames, not 40% more unless they charge extra for lifting a heavier sealed glass unit.

I've got double glazing in the vertical windows, triple in the Veluxes and the one I regret is double in a 1 x 2 metre skylight which given another go would have gone to triple for the extra few quid.

Glazers can be a bit economic with the truth - They can also be somewhat unprofessional when it comes to sealing the gaps around the windows which will make more of a difference than the glass.

I have found that when you start talking energy efficiency, things become a bit vague as the people you're dealing with don't know how to to a heat load calculation let alone know much about low e glass.

I'll follow this thread with interest if you wish to respond. Please understand that I only visit Lemonfool when I have spare time, so replies may take a while.

Regards,

B.

[neversay]

Thanks @PrincessB - I assumed that there was more to the manufacturing than just the extra pane of glass but, as you say, the 40% must be a large part profit margin. In the end, I have gone for double glazed as the sound insulation isn't an issue and the price difference paid for a couple more windows. I also stuck with plain white windows as it fits with the rest of the neighbourhood.

I did have one further question on choosing the glass for upstairs bathroom windows: does anyone know if Satin glass (or Pilkington Opal?) is any good compared to regular patterns?

Thanks again,

N.

(PS same here for slow replies as I'm travelling at present)

[PrincessB]

I did have one further question on choosing the glass for upstairs bathroom windows: does anyone know if Satin glass (or Pilkington Opal?) is any good compared to regular patterns?

Short answer - Satin glass is brilliant. Give Pilkington a ring and ask for a sample.

Longer answer - It blurs everything more than about six inches away into obscurity.
I've got upstairs road facing windows using it and I cannot make out there is a house on the other side of the road, it all blurs into a sheen.

Downstairs I've got front windows with upper clear panes and satin lower frames. The hedge is about five feet away and through the lower panes you can only make out the green on a really bright day.

As I've used clear and satin in one frame, it does give the option of having a roller blind which can give complete privacy along with plenty of light by half lowering the blinds, a dark room with the blind fully down for TV time and even more light when we're all dressed and decent.

You could jam your bottom against it and that would show from outside, no much else will though.

For dull reasons to do with fire control, I've also got windows using pattern glass that face next doors fence which is just under 1 metre away. I can make out the fence, next doors house and the sky, there is no comparison between the two.

Regards,

B.

[neversay]

Thanks @B. Taking your advice, I was going to try pressing my bottom against the glass but decided it wasn't appropriate in the showroom. I do have some small satin panels in the front door which seems fine but I do need to check it out with backlighting. I guess my main concerns are (i) the level of light reduction, and (ii) how it looks from the outside when the one bathroom window is opaque and the others clear. Decisions, decisions.

For the main house windows, I have stuck with double glazed and decided to replace a couple of additional windows with some of the cost saving. The 40% price delta for triple glazing has a long payback time and realistically we have the windows open for much of the year. Outdoor noise isn't an issue here but I did consider triple glazing on the front room bay to stop passers-by hearing all the internal noise we generate!

Oh and I stuck with white frames; it could be that the rest of the world is moving to anthracite grey frames but white is still in keeping with our neighbourhood and seems to brighten the place up.

N.

[malakoffee]

Double-glazing with etched glass versus obscure patterned glass . . . ..

I vaguely remember being told that obscured patterned glass loses a bit of the transmitted light, but nothing too drastic compared with CLEAR glass.

DAK the relative loss of light through the etched glass *. I assume more obscuration = more light loss ?

[jaizan]

You're only after a third bit of glass in the sealed units, so where does 40% more come from? I seem to recall that the difference for largeish windows was more like £40 for triple over double on my last build. Bear in mind that the frames are the same, so the only difference is the sealed units which are fitted into the frames, not 40% more unless they charge extra for lifting a heavier sealed glass unit.

ARE the frames the same ? The only way you get triple glazing into the same frames is by reducing the air gap, so the overall thickness is the same.
I'm not sure that's optimum for performance.

Conceptually, I agree with your direction. In an ideal world, triple glazing is like a 50% increase in the cost of the glass part and the frame should be a similar price. Even if the frame is thicker, much less than a 50% increase in price.

However, as double glazing is the standard mass market product, perhaps the triple glazed price considers some lower production volume frame sizes plus some higher profit margins.