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]

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,

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!

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.

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.

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.

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???

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.

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...

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

Come the Revolution ...

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.

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.

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.

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 £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.

No chance!