Fake Georgian Glazing Bars

Given that there are a few master builders on here I wonder what the answer is to trying to choose a sash window with nice Georgian proportions, and looks, and how to handle the glazing bars?

Windows will be triple glazed, so quite thick [between inner/outer glass]. There must be a thermal break between outside and inside ... stuck on the outside/inside/both will, presumably, look awful when you are slightly to one side of centre?

For me the look I would like is something like this:



but to avoid glazing bars we could go for single glass panes - can't find a good example, but something like this:



which I understand was popular at the end of the Georgian period; I suppose large panes of glass were expensive, so it was a demonstration of wealth, but we just don't think they look as nice.

 

Not seen any Georgian buildings with single large panes. Have seen a few 16C houses ruined by single pane double glazing though.

Only done secondary removable internal DG with sash windows.

 

The ones we are looking at are spiral-balance sash from Bereco
http://www.bereco.co.uk/products/Traditional-Sliding-Sash-Spiral-Balance.aspx
Our joiner is horrified that they use "bits of wood" - which when pushed he said meant "laminated" but did admit that his would be prone to some jambing at some time or another when they moved with wet. This isn't an original building so I don't feel precious about that, I'd like longevity and low maintenance, but they do need to look right, albeit perhaps not to a professional joiner

Its being built to passive house standards so insulation and U-value is paramount (so not many vendors in the Sash window market to choose from!)

 

Builder does a fair amount of "beautiful buildings" in the posher parts of London, and says that's where you would see them - I guess you've not been there Zigs?

Maybe that's the issue? that they are unheard of in the country, and why I feel uncomfortable with them?

I'd be happy with tilt-turn windows, provided they looked Georgian, although the window furniture would probably be all wrong? and if so that would put me off

 

Don't go to London if I can help it. Thought it might be a townie thing, i'd remember if i'd seen historic glass of that size, i'm very interested in it.

If you can stretch to a copy of this,

http://www.buildingconservation.com/books/bcd.htm

You'll find specialist contractors in there.

 

I've made quite a few Box frames, mostly replacements, but some for new build.
I'm not fully up on what is available regarding spiral balances, but if its fairly large I think you might struggle to find one capable of working a triple glazed window, the sashes will be heavy.

Personally I prefer weights, the real thing is much nicer.

I've never come across a triple glazed box sash, we mostly use a "slimlite" system where the double glazed unit is only 12 mm thick or so, otherwise you run into problems with glazing rebate depths and that thickens up the sashes and then the box has to be thicker and so on.

I think I'm right in saying argon/krypton filled units meet all the planning regs.
Just an example http://www.uaglass.co.uk/sashlite-ultra-thin-double-glazed-units/

As to glazing bars, you can have the real thing if you want, it just means using smaller units, but probably costs more.
We do a system whereby the bars are fitted to the sash on the inside, then the bars are framed up and fixed to the outside, so no separate pieces of wood.

Difficult to explain but its the best compromise I've seen.

 

The windows will be large; I've never come across spiral balances before (only sash cord that periodically breaks with catastrophic results to the glass in the window!!) so I will definitely check out how well it can support the weight, thanks. Not sure how "authentic" it is, but I have seen things that look like bicycle chains in place of sash cord, maybe that is an answer (with a "never-fails" lifespan?!)

Passive house much more demanding than building regs ... windows are required to
have a U-value [entire window, not just the glass] of 0.8 W/(m²K), which they say is about twice as good as normal new windows (the ones in your link say 1.6 or 2.0 :( ), and the internal surface must stay above 17C even on the coldest nights. The building should need pretty much no heat input at all - maybe a 1-bar-fire per 3-bedroom sized house at -10C (it is common for no central heating to be fitted, the money saved on the central heating system and installation is spent on extra insulation instead, but benefit of negligible heating cost is for the lifetime of the building of course). The walls are massively thick, to accommodate the insulation and to allow for the inner blocks which are wider than normal (and more dense, for thermal mass), so there is plenty of room for additional thickness, as such, and being able to get the reveal correct (slight over-simplification as the insulation has to be contiguous, so you can't place the window "anyway" in terms of front-to-back, but in general the wall thickness is generous enough).

That's a very good point, hadn't thought of that <SlapsForehead!> I'll check. I suspect it is harder to get the required U-value when using smaller units, but its definitely worth enquiring, ta.

 

Thanks Zigs, although I don't need authentic, just a good fake

There is a Passive House advisory whatnot, and they have recommended suppliers (who's windows have been tested and passed the requirements), so I'm comfortable with that, just needing to make an aesthetic choice over how the glazing bars will look

 

Here's the low-down on Passive House glazing, for anyone interested in the technical details

http://www.passivhaustagung.de/Passive_House_E/window_U.htm

 

I've only seen chains on massive sashes in commercial buildings, these days you can get nylon cord, it lasts longer and is much stronger than the old stuff.