When replacing original sash windows, how much is removed?

[d000hg]

Ah, I was just being daft then. Googled how to replace a pane in a sash window and it makes more sense. The glass doesn't slide into a precise groove (you'd never get it in/out!) but from the outside looking in, the glazing bar/stile/rail is routed or similar to have a 'stepped' profile. So the glass butts against this with a small overlap, then you apply putty on the outside to lock it in place.

Have I got that right?

 

[geraldthehamster]

Putty on the outside, yes. The glass sits into a rebate in the frame. It's usually held in place with little glazing brads (nails), then putty is applied.

 

[d000hg]

Rebate, that's the word I wanted

Does that imply that if the glazing bars and other wooden pieces are deep enough, one can retrofit double-glazed panels to the existing sash by deepening that rebate? I assume my glass is probably 3-4mm right now and it seems the thinnest double-glazing is 10mm (3+4+3) though how much benefit that gives I am not sure.
Looking at the window in my original photos, there appears to be at least 18mm depth on the inside which rather suggests this is feasible. The sash itself has 35mm spare in total, the 18mm is to the edge of the 'chamfered' bit, so clearly thick glass would physically fit but that looks like a bigger job and...

Of course, while glass panes are fairly cheap (£100 for a whole window) I don't know if this would work out much cheaper than having brand new wooden sashes made for my existing frame. I suppose it probably would since brand new wooden sashes are very expensive and would possibly not be built with the same craftsmanship and quality wood anyway.

I'm half tempted to get hold of an old sash window ripped out of someone's house in favour of new UPVC, and have a play with it as a test-bed.
Have to get a window guy out as well although finding one who can advise on both renovations as well as new windows might be trickier.

 

[Tigercubrider]

http://www.sashglass.co.uk

example not recommendation

 

[d000hg]

Good grief that's thin.

Actually I might have been dozy before... I was assuming I'd have to deepen the rebate into the window. But looking externally, the depth from the glass to be flush with the outside of the sash is ~10mm. Is that what we mean by the depth of the rebate i.e. mine is about 14mm in total if I have 4mm glass? The dream would then be that a new unit can fit in place without having to deepen the rebate at all?

 

[geraldthehamster]

Could be doable. You'll lose that single glazed feel that you said you liked. Although you'll keep the original box and sashes.

I still think this is only worth considering if you are conscious of draughts and cold that you can put down to the windows. I wouldn't personally consider doing it on the vague notion of saving energy costs. I lived for many years in an Edwardian Terrace with original sashes throughout (and in fairly poor state of repair). I never had any problem keeping the house warm.

 

[d000hg]

I'm curious about the "single glazed feel" - is this something generally acknowledged? It's strange because even though the glass is not perfect - I think we have some original panes which are very wibbly-wobbly - you feel like there's nothing between you and the garden in a way that is hard to explain. Having moved from a more modern house, I am wondering if it is the single glazing, or simply the fact the windows are so big; the feature bay sash windows use glass panes which are slightly larger than 50x80cm each and these are just wonderful.

Are there real (non-subjective) reasons why modern double-glazed glass would seem like more of a barrier... some way the two layers of glass interact somehow?

 

[geraldthehamster]

I know what you mean by that. I think the wibbly wobbliness is part of it; it feels like something real, rather than something industrial and regimented. Double glazing is also quieter. It dampens the sound and cuts you off from outside (possibly this would be what you wanted if you had traffic noise, though secondary is better for that).

 

[d000hg]

regarding costs: I'm fairly sure the EPC report gave estimates of savings due to specific measures we could take, though I don't have it to hand - we're pretty much at the very bottom of that graph and it certainly mentioned windows as a factor.

The big bays in the reception rooms are basically 2x1.6m walls of single-glazed glass. I think they were painted shut which is the traditional method to reduce draughts - if we wanted them to open and be draught-free that is perhaps where the problems really come in. They definitely don't look like they could be replaced except like-for-like, they are very elaborate. Maybe the original housings can be made draught-proof though.

 

[geraldthehamster]

EPCs are of doubtful utility. We got a low report because we had incandescent light bulbs...

Well maintained sash windows shouldn't be particularly draughty. They'll let some air circulate, which is good if you want to avoid condensation. I've been in plenty of houses where double glazing was kept shut all the time, and mould developed on walls.

Your house, your windows. I wouldn't change anything unless you feel the house is cold, and even then I'd look at other remedies. You wouldn't rip out your original fireplace or cornicing...

 

[d000hg]

Most Victorian houses, the fireplaces have been ripped out except in the living room typically! Luckily ours seems to have either the originals or they've been put back in though of course most of them are blocked up... for efficiency in favour of modern central heating. We actually want to open some back up because we have so much free wood we can heat rooms for free with open fires/stoves.

It's always a compromise I suppose when it comes to old houses. The lack of cavity walls might be our biggest issue!

 

[endecotp]

Regarding putting DG units in existing sashes, e.g. http://www.slimliteglass.co.uk/

I was told to budget about £75 per individual DG unit. My windows are 6 over 6 (Georgian). That gets expensive. With newer Victorian windows i.e. 2 over 2 it's more affordable. Get them draughtproofed at the same time.

I was told that the sashes would be taken away and the rebate routered deeper so that the external face of the glass would be in the same position. The weights have to be increased to keep them in balance.

My eventual plan is to do this eventually to my internally more prominent windows i.e. living room. For the bedrooms, the windows are largely hidden by net curtains and soundproofing is also important, so I'm going to fit secondary units there.

Ask an estate agent what effect scrapping your original Victorian wooden sash windows and replacing them with plastic ones would have. This will depend on where you are. (Serious suggestion.)

 

[geraldthehamster]

We actually want to open some back up because we have so much free wood we can heat rooms for free with open fires/stoves.

Do a smoke test if you're going to use the grates, to make sure the flues are sound. If you're going to install stoves you'll need flue liners anyway.

Cheers
Richard

 

[d000hg]

Regarding putting DG units in existing sashes, e.g. http://www.slimliteglass.co.uk/

I was told to budget about £75 per individual DG unit. My windows are 6 over 6 (Georgian). That gets expensive. With newer Victorian windows i.e. 2 over 2 it's more affordable. Get them draughtproofed at the same time.

I was told that the sashes would be taken away and the rebate routered deeper so that the external face of the glass would be in the same position. The weights have to be increased to keep them in balance.

My eventual plan is to do this eventually to my internally more prominent windows i.e. living room. For the bedrooms, the windows are largely hidden by net curtains and soundproofing is also important, so I'm going to fit secondary units there.

This seems a reasonable compromise, we were considering the same kind of idea. Your quoted cost of £75 per unit - was that for the glass alone or the cost including the work to re-balance and draught-proof them?
The site you linked to doesn't appear to list prices (worrying!) but this site they seemed to come in more like £27 per pane (http://www.sealedunitsonline.co.uk/)

Do a smoke test if you're going to use the grates, to make sure the flues are sound. If you're going to install stoves you'll need flue liners anyway.

Cheers
Richard

I was under the impression that if I open up a closed fireplace/chimney, it then is subject to current building regs and I'd have to get a modern flue/liner. Which seems a shame since heating the breast in the room above is surely one of the benefits.

 

[d000hg]

Another point is that some of our windows are painted shut - the cheap way to cut out draughts. I imagine some of the windows we'd never want to open - if we were replacing them we might get sash-style non-sash windows and reduce on cost.

But by the same logic if we were reglazing with low-profile DG panels, could we avoid re-balancing and draught-proofing to similarly save on work/cost? We'd be keeping the original window for its period feature value but turning it into a modern, non-opening DG version. It's only June but so far we have not found ourselves wanting to open windows except in the bedroom - it's fundamentally a nice cool house. We should live through the summer to validate this but the fact the feature windows are sealed shut suggests it's an option.
Out of curiosity why did they put sash windwos in every room instead of sealed ones? Why the need to open all the windows back in 1880?