A couple of eyebrows raised at the idea of an "elegant" 3g "Georgian sash window" with "insulated wood frames". But we know what you mean. Just make sure the wife does though, because the reality may not match her expectations in terms of the look normally associated with a "Georgian sash window", the elegance of which comes from its slim proportions.

Vrogum do just what you need, but only double not triple glass - still, as good as you can get at present. Google for Vrogum, or Winchester Joinery, one of their UK distributors. They are premium-price tho, for no apparent reason, even in their ordinary casement ranges.

Vrogum are unique, in that their opening sashes are glaze-in - everyone else (scandinavian-type) is glaze-out. That means, the way they do it, glass face is close to the sash outer face, with just a small splay of timber showing , almost exactly like a trad putty line. All others show bulky loose beads, glass inset at least 25mm from sash outer face. A sliding-sash fixed frame will be completely buried behind 'masonry' (or EWI) so only the sliding sash itself shows, less staff-bead width. Should be only slightly bulkier than a trad sash, on face, tho of course deeper than trad 44mm in-to-out dimension - but you'll not notice that.

Buy with single 2G unit for each sash - no structural glazing bars. Then apply your own grid of 'fake' glazing bars, as flimsy as you like, carefully mitred together and scribed over the edge beads, fixed with top quality double sided tape inside and out.

I find that refraction/reflection of glass, plus dazzle from the sky, makes it hard to see what's in the interior of a 2G/3G unit, unless you really try hard.

http://eurostylewindows.co.uk/sash_window_gallery - looks impressive. Needs more detail photos, but looks like glaze-in, as I described above - no view of outside 'putty line' shown. And are those fine beads glue-on? No reason, other than interchangeability with extg as replacement window, whi couldn't be fattened in in-out direction, to take thickened glazing unit. Even 3g, using that Heat Mirror lightweight plastic film http://www.albo.co.uk/what-is-heat-mirror.htm as middle pane.

What size can pics be?

Noticed it says "Listed Buildings & Conservation Area Approved". Don't depend on that being the case. Most (granted not all, but they were singular exceptions) COs would reject d/g out of hand just because it was d/g. You can see why in the reflections in the window.

And we haven't mentioned the potential problem of accommodating balance weights of sufficient size, which means spiral balanced sashes, in which case you don't need the deep rebated reveals to achieve that 'part-hidden frame' look because the frame can be of a shallow section and fixed to the standard reveal of a new build.

For the info of anyone not familiar with them, the bars on that sash in the pic are duplex - stuck on. You can see the spacer in the unit between them. Failure of the unit in one section means replacing the whole unit.

Happen to agree with you about spiral balances, and not just about the comparative "roughness" of operation. Like failed units, when they go (and they do) you only get an argument and a replacement balance from the supplier, the cost of replacement having to be borne by you.

But sometimes, as always in the real world, you have to do what you have to do and go with what you can get away with under circumstances outside your control.

The "problem" with 2g in sashes is having BOTH sufficient clearance within the box frame and sufficient height to allow the heavier and usually longer weight to operate over the whole distance of the sash's travel. I'm lucky with mine because they're very tall, but some I've worked on have been almost square and haven't had sufficient height for the travel and I ended up having to use balances fixed to the original frame and channelled within the sash stile. It actually doesn't look too bad because few people actually look AT a window as they walk past - unless they're in an exhibition hall looking for high performance sash windows!

Knowing nothing about sash windows, but reading this thread about the problems of getting counterweights in a narrow space, and of springs that break, has anyone looked at using gas rams? They are pretty reliable now, and thin (the sort of thing that holds up the hatch on a car). They also tend to be smooth and fairly silent.

Just a thought from someone with no knowledge of these things............

How thick (in to out) were your sashes; what spacers in your 3G units; how massive your weights, with 3 glasses to balance?

Hi Joiner, on a side note I'm looking for aluminium flashing strips to surface fix to existing windows to enable me to retrofit triple glazing. Was there an Irish company you used?

And Tom, you never mentioned that when you use the single weight system, the lighter side sashes have to be "braked" because the shared weight is too heavy for it, being balanced with the larger central sash.

I thanked the gods for George Ellis once again on this job because he describes how to "brake" the smaller sash in this type of set-up. As usual, it's simplicity itself, although it was surely a eureka moment for whoever first thought it up. Ellis describes a cork ball that sits in a rounded hole in the side of the sash, the hole of just such radius to allow the ball to rotate whilst offering some resistance against the pulley stile. He doesn't elaborate, and appears to trust to luck to get that resistance just right, but he's a guy I've come to trust over the years!

Cork balls not being available at the local ironmongers (!!!) I was left with a problem if I couldn't think of an alternative, and fixing the side sashes wasn't an option, having already assured both the customer and the CO that it wouldn't be a problem. The answer (isn't it always?) was sitting on my desk in front of me. The ball out of a computer mouse. It works. You do have to operate the side sashes slowly or they jam, but it only requires a slight downward movement to free them off. Raising them is "interesting" because the ball sits in the bottom of the recess, so it's there that trial and error at the assembly stage comes into play. I eventually had recourse to the blow torch to scorch the surface of the recess and 'polish' it (don't know whether this would work on anything other than oak). I did think this would reduce the friction needed to brake it, but in fact it made no difference on the downward movement whilst giving a free-ish run upwards (which is when you need the resistance). I did find that it needed the balls on both sides of the sash to equal out the resistance and stop tipping.

I was annoyed with myself for making a promise I didn't otherwise have to make because fixed side sashes are perfectly acceptable and, because these were such a faff to operate, were reportedly never used because the customer said she couldn't operate the top sashes anyway, being "only little", and so the bottom centre sashes only were used. That was four years ago and the guy who does the painting said he'd been told to "just paint over them" when they were done earlier this year. No wonder I fell out with her!

I'd recommend that George Ellis book to anyone who thinks that the modern stuff was only thought of this year... http://www.amazon.co.uk/Modern-Practical-Joinery-George-Ellis/dp/0854420398/ref=sr_1_1?s=books&ie=UTF8&qid=1319185879&sr=1-1

At last - first sighting in-the-flesh of a long predicted phenomenon - the 3G sash window. The CERN Higgs hunters should take a leaf ... Just add stick-on glazing bars and even a Listed Buildings Officer wouldn't detect the too-smooth but sucked-in reflection typical of multi-pane glass units.

Posted By: JoinerIncidentally, how would the thickness of the rebate on which the unit is bedded affect "cold bridging"? In other words does a greater thickness of section insulate the unit better?

Hi Joiner, We put a strip of AeroGel around the frame before we attached it to the brick wall, is that what you mean?

Pugliese, having researched the options for renovation of my Victorian house, I have recently had some "Slenderglaze" windows made by www.sashconsultancy.co.uk. They haven't been installed yet, but I previously visited a house that had them, and was impressed. They are unusual in having a structural, rather than stick-on, glazing bar.

They told me that if they were putting windows in new frames, they would typically make a 46mm thick sash (containing a 16mm glazing unit, which has an 8mm gap). For this their website quotes centre-pane U=1.5. While they are slim, the U values could be a bit better, but I think that's a compromise you have work out.

Although it's not relevant to you (or to me), apparently a lot of their business is in replacement of sashes in original frames, which means they have to make them really thin - the ones I saw were 35mm sashes with a 6.4mm spacer.

And my question 3 posts above was a genuine one.

Is it worth triple-glazing a sash (with full draught-exclusion, including the pulley stiles) if the benefit of the triple-glazing is lost through a thinner framed section to house it? The object (taking on board all the thinking on here about "every little helps") being to get as many bangs to the buck as possible.

I doubt there are any calculations out there to assess such a situation, but I just thought that there must be SOMEONE who's spent enough time working things out to the nth degree to have an instinctive/intuitive take on the matter, insignificant as it might seem. Pretty please?