Green Building Forum - Slim double glazing

Slim double glazing

WeeBeastie — Wed, 31 Aug 2011 15:55:14 +0100

Slimlite double glazing (as seen on Grand Designs) seems now to be patented. But I have just spoken to a glazier who says he can have slim units made by another company. Both would carry a 10 year guarantee, and the quotes I've received are almost identical. So what's special about Slimite? Is it the gas(es)? Slimlite has published U-values, and the other supplier may not (I haven't asked him yet), but could the gases in a slim cavity make any real difference?

The only other thread I could find on this topic basically said that anyone can manufacture a unit with a slim cavity, and you can request any gas you want....

So how should I make my choice if I decide to go ahead (and it has to be slim units in my original sashes as my property is listed)? Is Slimlite actually better? Or do I do a bit of sleuthing and find out who has the best reputation??

Slim double glazing

Joiner — Wed, 31 Aug 2011 16:08:39 +0100

The "benefit" of Slimlite is the sightline, not necessarily the slimness of the units, meaning the distance across the unit, because any unit manufacturer can (whether they will or not is another question) make a unit with a make-up of 4-6-4.

Up until a couple of years ago I used to use the 14mm units a lot, but suddenly found I couldn't get them gas-filled because drilling the hole to gas fill them was too tight a job. Don't know whether any manufacturer would gas-fill using the gas chamber (bath) process - it would certainly get around the problem with the hole - but none of my sources will do the 14mm any more.

Going to 16mm isn't a problem for them and they'll happily do that...

[IMG]http://i54.tinypic.com/ayv7g1.jpg[/IMG]

Slim double glazing

Joiner — Wed, 31 Aug 2011 16:21:59 +0100

The problem with Slimlite has been the reports of their unreliability. There was another thread on this issue, but I'm buggered if I can find it, where the guy was a bit sceptical of the bad vibes being given off about Slimlite, but then came back with a report that seemed to substantiate the doubts about their reliability.

What you have to remember is that a manufacturer can guarantee their units for a thousand years in the certain knowledge that if they fail in a year's time all they're liable for is a replacement unit. It's the poor sod who fitted the originals that has to cover the time and expense of replacing the bloody thing. And insult is added to injury by the manufacturer doing everything in their power to avoid admitting it was due to a fault on their part.

Slim double glazing

Joiner — Wed, 31 Aug 2011 16:23:22 +0100

Got it!

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=2516

Much of that discussion eventually went into whisper mode between me and the last poster because Slimlite was taking something of a bashing. A link was given by him to this site...

http://forum.expertexpert.com/viewtopic.php?f=9&t=42,

Slim double glazing

WeeBeastie — Wed, 31 Aug 2011 16:36:46 +0100

I have Listed Building consent for 6mm cavity, so presumably the sightline would be the same regardless of whether it's the patented Slimlite or the alternative from anybody else willing to make them? Sorry, I am a just a layperson!

Thanks.

Slim double glazing

Spike — Wed, 31 Aug 2011 16:42:53 +0100

You should scheck whether the units are compliant with all parts of BS1279. I don't think Slimlite are and the only company that claims to be (as far a as I know) is Histoglass. Which companies are offering 10 years guarantee? Best I could get was 7 years!

Slim double glazing

WeeBeastie — Wed, 31 Aug 2011 16:43:07 +0100

Joiner, sorry just got your subsequent posts. I've read that thread! That's really why I asked a second glazier (who happened to be here for another matter) about Slimlite. He certainly had a strong opinion on it, though couldn't comment on the reliability issue. He's confident his alternative supplier will produce an excellent quality product, and accepts that it could be his own time that would be needed to fit a replacement should the original fail!

I'm very tempted to go ahead in just my living room for the moment, as it has a large glass-to-wall ratio and despite draughtproofing was near impossible to get comfortably warm during last year's winter. I'm just confused who to get the stuff from....

Slim double glazing

CWatters — Wed, 31 Aug 2011 17:24:45 +0100

Just for info the 4-6-4 units I mentioned in the thread Joiner posted have proved more reliable than the thicker sealed units we have elsewhere in the house. None of the 4-6-4 units failed where as two of the wider ones have.

Slim double glazing

Nick Parsons — Wed, 31 Aug 2011 17:31:04 +0100

My experience as yours, Colin. My 4/6/4 units are 25 years old and the only one which failed did so because I dropped a scaff board through it! 2 no. 4/16/4 units made much more recently have failed, and I often see failures in under 10 years. Nick

Slim double glazing

Joiner — Wed, 31 Aug 2011 18:48:56 +0100

I think the one thing that comes out of experience with double-glazing is that there is no such thing as a guaranteed unit, as against a unit with a guarantee. Subtle difference but a big one.

And interesting you say that about the 14mm units, Colin and Nick, because I used them for a VERY long time and none of them have been reported as failed; none of them was gas-filled either, which isn't significant because it was a LONG time ago, before even FENSA was thought of. Mind you, of the 24mm units I've only ever had two (although three comes to mind for some reason I can't cite) have failed, and then within days of fitting, both in the same top-hung vent - the replacement third one is still sound after five years.

According to my glazing supplier, one of the reasons for poorer quality is the poorer quality of the workforce, in one case all of the factory floor are of east-European origin, even the foreman is Polish. Although in fairness, in this instance the "poor quality" relates to a failure to follow specs. I never want tape around my unit edges (it was the cause of a major breakdown on a job I was called in to rectify - that conservatory I was trying to get someone to take on again a while back) but despite it being clearly stated on the spec sheet they frequently come back taped. Not a major problem, but irritating to have to take the trouble to remove it when it shouldn't have been on there in the first place!

As to the original question!!!!

I can't for the life of me see why anyone else shouldn't be capable of making a unit similar to the Slimlite one, and I'm gobsmacked that they apparently have patents on the design - which would explain their incredibly high prices.

It's always going to be a risk reducing the section of the spacer bar because that's where the failure is going to be every time. Impossible for it to happen elsewhere on the unit! Glass-to-spacer-bar adhesion has to be immaculate and reducing the area of contact is a risky business, especially when you've reduced the sightline to half that of a conventional unit, which is the USP of Slimlite. Maybe they have developed a super-duper incredibly-adhesive-topped-with-an-amazingly-efficient hot-melt. Depends on whether you're prepared to give them the benefit of the doubt. Personally, I can't afford to.

Slim double glazing

fostertom — Thu, 01 Sep 2011 15:23:17 +0100

Posted By: WeeBeastiepresumably the sightline would be the same regardless of whether ...

Are you clear that 'sightline' means the spacers are extra-slim in width, regardless of the 6mm depth? Standard-width spacers of 6mm depth are easy - maybe only Slimlite make the narrow-width ones.

Slim double glazing

nigel — Thu, 01 Sep 2011 17:08:42 +0100

I looked into slimlite units to improve my sash windows but I came to the conclusion that unless draughts were completely eliminated there would be very little benefit for the high cost.

I also realised that in the fine glazing bars of the georgian sashes it would be likely that the perimeter seal edges would be visible from the inside and the outside.You need to check the rebates on your windows the slimlite units need a minimum rebate of 7mm otherwise the edge of the seal will be visible.

I concluded that secondary glazing would improve thermal properties and stop draughts more effectively at lower cost.

Slim double glazing

Joiner — Thu, 01 Sep 2011 17:15:18 +0100

Yeah, "sightline" seems to throw a number of people.

It's what you can see of the unit at the edge of the bead.

Nothing but glass, the spacer being level with or slightly below the bead edge = good.

Obvious sight of the spacer bar above the edge of the bead = bad.

When double-glazing first took off you could see some horrendous sights. When my son wanted to double-glaze the windows in his Listed cottage the CO said she didn't mind "as long as I can't see the silver foil".

Confusingly, mouldings on the edge of the glazed area can give a "better" sightline by making the glazing bars look slimmer than they are, when the effect is visual rather than actual. Ha ha. That makes sense to me anyway!!

Slim double glazing

WeeBeastie — Thu, 01 Sep 2011 19:10:56 +0100

Thanks for clarifying exactly what the sightline is - none of the glaziers I've spoken to had done that properly.

I too looked into secondary glazing, but I'd really like to keep my working shutters (yes, maybe style over substance & financial sense!). Windows already draughtproofed but the single glazing still leaves a huge cold area to one side of the room. And I'm always baffled by the argument that shutters and thick curtains are as good as double glazing - what about daylight???

Slim double glazing

Joiner — Thu, 01 Sep 2011 19:47:35 +0100

You don't get that much in Scotland - allegedly!

Slim double glazing

nigel — Thu, 01 Sep 2011 22:35:43 +0100

Storm make a secondary glazing system which fits into the space provided by the staff bead on your sash windows which means they don't interfere with the shutters.

I had a quote from them which seemed a lot for what they are so I have decided to make my own.

Slim double glazing

fostertom — Thu, 01 Sep 2011 23:27:37 +0100

Knock out all the glazing bars, increase width (and maybe depth) of perimeter rebate, put in a single 2G unit with full-width spacers, apply stick-on beads inside and out, incl a matching moulded greater-width glazing bead planed off flush with the sash inner face and decorated invisible (wait for spittle!).

Or better, make the sashes new, of extra depth, say 56mm, using some of the spacial zones of staff, parting and outer beads, and fit 2G units with gap 12mm wider than will fit into 44mm sashes.

Slim double glazing

WeeBeastie — Sat, 03 Sep 2011 07:23:34 +0100

fostertom - wish I was allowed to! Listed Building...

nigel - will check out the Storm system, but I have the various fittings for opening the windows attached to the sashes and surrounds that would get in the way.

joiner - you're right! If I could knock down the terrace opposite I'd get a bit of solar gain in the winter. Darn those Listed Building people again...

Slim double glazing

Joiner — Sat, 03 Sep 2011 10:02:48 +0100

I've had this discussion with another guy on another forum, but much of it was done via PMs, although I'd like to copy my text out into the open forum so that others with the same problem could see the suggestions. It's here...

http://www.ebuild.co.uk/community/topic/10446-double-glazed-timber-sash-windows/page__pid__62696#entry62696

I'll try and put the PM'd posts onto the main forum this weekend. (It's not a forum I spend any time on now because of the amount of spam that gets on there, including an irritating tolerance of blatant spamming via "address urls", which are wide open to abuse.)

I doubt you'll get much joy out of your CO as long as secondary glazing is available, because it's non-invasive and therefore reversible. I agree with Nigel that the cost of secondary glazing is unjustifiably high, but that doesn't surprise me if you get a quote off Storm. Duration Windows (no commercial interest, have just used them a lot in the past) have an online calculator which is useful to get a comparison quote: http://www.duration.co.uk/aspsec/introduction.asp

Slim double glazing

fostertom — Sat, 03 Sep 2011 10:45:08 +0100

Posted By: WeeBeastiewish I was allowed to! Listed Building...

Come the Revolution ...

Slim double glazing

Joiner — Sat, 03 Sep 2011 10:58:11 +0100

Ha ha. Which one is you?

http://www.tolpuddlemartyrs.org.uk/index.php?page=photo-gallery&img=47

Slim double glazing

fostertom — Sat, 03 Sep 2011 11:03:37 +0100

Posted By: JoinerI'd like to copy my text out into the open forum so that others with the same problem could see the suggestions. It's here...

Luvvly looking - truly authentic AFAICS. Except the bulky glazing bars - are they as original? - a serious in-your-face flaw, if not.

Such fat bars wd only be right for v early Georgian, say pre-1730. Never since, AFAIK, thro Georgian, Regency, Victorian, Edwardian, right up to 1930s bank-branch.

As a solution, even with new sashes let alone all-new incl box frames, such fat bars are definitely not a good solution. Neither technically nor visually nor cost-wise. Nothing going for it - except the notion that stick-on bars on a single 2G (or 3G) unit are the devil's work, creating visual effect that's forever jarring.

Having gone the stick-on route many times, incl in finest Listed buildings up to 20yrs ago before the doctrinal purists took over LB theology, I and my clients have found that 'nothing there' effect (when you squint sideways looking for trouble) to be completely acceptable and preferable because that preserves the delicate effect of thin bars, which is all you see against the light 99% of the time.

That delicate tracery, against expectation, actually enhances the feel of panoramic transparent link to the outside (compared with no-bar 'picture windows') but fatter bars give a caged-in effect, as you'd expect.

Slim double glazing

CWatters — Sat, 03 Sep 2011 11:04:59 +0100

Just wanted to add that spacer bars come in different colours. Can get brown, bronze, black, white(?) etc. Make sure to specify when ordering. Also check need for toughened glass (depends on the height above floor level).

Slim double glazing

fostertom — Sat, 03 Sep 2011 11:14:30 +0100

Posted By: JoinerWhich one is you?

http://www.tolpuddlemartyrs.org.uk/index.php?page=photo-gallery&img=47" >http://www.tolpuddlemartyrs.org.uk/index.php?page=photo-gallery&img=47

I was there, in spirit. See the film http://www.tolpuddlemartyrs.org.uk/shop/product.php?productid=17537&cat=274&page=1 .

We visited Tolpuddle on way back via Portsmouth ferry from a Normandy hol, where the reek of old money still fencing off the whole idyllic countryside with nowhere to walk, was tangible. Called in at a country house open day, where the local tory bigwig's union jack was flying, having just defeated the last remaining labour MP in the SW (except Plymouth), and feudal local lackeys directing the car parking. Then to Tolpuddle, breath of fresh air, and on to Tyneham where the film was made - village taken by War Office 1943 and never returned, despite Churchill's personal promise to the inhabitants. Somehow, the hidden reality of things revealed.

Slim double glazing

fostertom — Sat, 03 Sep 2011 11:22:41 +0100

That link http://renegadeconse...-value-windows/ within

Posted By: Joiner
http://www.ebuild.co.uk/community/topic/10446-double-glazed-timber-sash-windows/page__pid__62696#entry62696" >http://www.ebuild.co.uk/community/topic/10446-double-glazed-timber-sash-windows/page__pid__62696#entry62696

what's the guy talking about, ingeniously complying with Uw 1.6?. It's so completely inadequate as to be laughable.

Slim double glazing

Joiner — Sat, 03 Sep 2011 12:26:08 +0100

Yeah, he's to be taken with a pinch of salt, but tragically he does represent the general glazing population!

As to the glazing bars - that's what you're stuck with unless you go the duplex route, and we've been there before on here.

Those 36mm bars can be reduced to 33mm, but visually you'd be hard-put to know the difference of that 3mm. The bars on the original windows here are 25mm, which are (as you point out) themselves considerably thicker than the original bars on original (and Victorian "georgian") Georgian sashes where I've made them as thin as 1/2" (13mm), but of course single-glazed.

In the flesh, as it were, these glazing bars don't look as "in your face" as the pics might indicate because the effect of the light on the spacer bar/external bead against the darker aspect of the internal section actually makes the bars look slimmer than they are. The point that you actually look through, not at, a window is one not many people think about until it's pointed out to them. Trouble is, once it's pointed out to them they then become conscious of the friggin window.

Incidentally, often one of the first signs of a sash window being "old" (as in REALLY old) is the thickness of the glazing bar. It was the first thing I noticed on one job where the owner of the Listed building (recorded as medieval in parts) had called me in because he thought it strange that the CO had suggested replacing them with new windows after only a cursory visit to complete the paperwork. Further indications got me to thinking that they might be examples of the earliest sashes. Getting EH off their backsides for a second opinion proved a real problem, but the owner listened to my plea to hold fire and eventually a new CO with the right contacts got John Yates down who confirmed them as early 18th century, vernacular rather than grand. I also got the job to do the windows on the neighbouring building and the pulleys on some of those were made of boxwood, only the spindle being metal. Now that's old.

As this place is vernacular architecture, being the old offices (built in 1848) to the colliery that was here until the 60s, finer architectural details are not in evidence! The windows in those pics are in the building's extension, built sometime between 1905 and 1935, and all the windows are without horns.

Slim double glazing

fostertom — Sat, 03 Sep 2011 13:23:31 +0100

Fascinating. Yes, it's credible that colliery offices wd have bars more 'durable' than refined! But no horns?! How the typical Bath sash with meeting rails only 15mm high and no horns hang together is a mystery - structural glass and paint, probably.

Slim double glazing

Joiner — Sat, 03 Sep 2011 14:40:40 +0100

And good wedged joints. I've taken them apart and cleaned them up by doing nothing more than taking out the wedges after deglazing. Oh for the time and the customers who can afford to pay for that time!

The trouble with meeting rails of that section is that you usually find them painted shut because the area where the catch is located is chewed all to hell and all you have is a catch more or less sitting uselessly on rusted 1/2" woodscrews of some age, all of which usually pulls away with your fingers. It's a situation where two-part epoxy resin comes into its own, preserving all the original material, except that some COs of the (as you put it) LB purist camp object to its use because it isn't a traditional material/method, preferring a new rail to be made replicating the old one, which goes against the spirit of "repair not replace".

A lot of the windows here were replaced when the place was two council flats, the council having bought the building together with all the land of the country park, the adjoining quarries and half the (mining) village for about Â£57,000 back in the 60s, so they're "a bit utilitarian", mouldings having been applied with a router after the sashes had been assembled, so with rounded corners.

Before we bought the whole building, the upstairs flat was owned by a girl who'd sold her London flat for a quarter mill. She paid cash for the one upstairs, plus a cottage in the village to rent out. She told her London friends that she lived in an ex-council flat. Their faces on arrival were a picture.

If I had more faith in the duplex bars and the required units I'd also prefer them.

Slim double glazing

JSHarris — Sat, 03 Sep 2011 14:59:54 +0100

Posted By: Joiner(It's not a forum I spend any time on now because of the amount of spam that gets on there, including an irritating tolerance of blatant spamming via "address urls", which are wide open to abuse.)

The tolerance for spammers over on the other place is really beginning to bug me, too. I cannot for the life of me understand why any company can think that starting off by deceiving potential customers is a good advertising strategy.

Anyway, enough of my off-topic rant. I just hope that this place doesn't go down the same path.

Slim double glazing

Joiner — Sat, 03 Sep 2011 17:44:08 +0100

No chance!