Insulating old windows

That type of window, at this stage, is probably a rare beast! Worthy of retention.

You could investigate having the single glazed panes replaced with a very thin double glazing (but as thick as the steel frame will allow). There is a Scottish company that does double glazed units with gap down to between 3mm gap specifically for ‘heritage’ windows (google slimlite). This would help but may not do a huge amount for the overall thermal efficieny of the window as a whole, as the steel elements will still suck the heat out!

The other (probably better/cheaper) option is to look at a secondary glazing system internally.

I’d like to see some photos of these :angel:

Aside from the good suggestion just made by DOC, I offer the following notional ideas:-

1. Put new double-glazed window just inside original windows – a kind of translucent internal shutter – in such a design as the framing of the internal window makes minimal visual disruption to the pattern of the original one to insiders.

2. Remove and measure the original pattern of steel framing so as to have a precise design for new double glazed Crittalls with the original design. Install new double glazed windows. Sell the old Crittalls over internet to a worthy home.

cf. http://www.youchoose.uk.com/replacement-crittall-windows-local-planning-authority.html

Those don’t look too bad, Teak.

These all sound like good ideas, but a little expensive right now. Might mooch down to the museum on the quays and ask them how they did their plastic-blinds-style winterising.

Incidentally, I did think of replacing the Crittall windows – a huge U-shaped window on the side of the house, windows flanking the door in the kitchen and the main window in the scullery, the window by the front door, and large french windows with smaller windows on either side in the dining room. But when I rang Crittall, they told me that to replace just one of the small flanking windows would cost £5,000…

Yes, I remember in Property Ladder about six years ago, where a couple were restoring an Art Deco house, they spent about £25,000 (bearing in mind ‘local money’, and a while ago) replacing original steels with Crittal reproductions. It’s no wonder you got the price you did, Tighin: steel frames from the UK (and especially with today’s metal prices) are notoriously expensive in Ireland.

Slimlite is certainly an option, but the key point is the structural integrity of the existing steel members. If they are 1930s, they will not be galvanised, hence I imagine they’re not in as good condition as late 1950s frames, so they will have to be carefully assessed. Slimlite also cannot be installed using the existing single-glazed metal clip and putty system – rather it is siliconed in position, allowed to set, and is then puttyed over to maintain the historic profile – this is usually achievable. The cold bridge of the steel sections is unavoidable – something that has been ironed out with a thermal break incorporated in new steel frames – but in the context of the overall expanse of glazing it is not considerable. It is worth speaking to a specialist on the potential for condensation issues at junctions. Lambstounge Ltd. is the only supplier of Slimlite glazing in Ireland and is definitely worth talking to.

Personally, I would be reluctant to install any expensive glazing in existing steel frames unless they were fully assessed by a metalworker for their integrity. Even then, 1930s glass has characterful imperfections – visible even as late as the 1950s – which can be worth retaining. Generally speaking, an overhaul of existing steel frames coupled with tailor-made, internal timber secondary glazing featuring sections that respect the pattern of the originals, is an option I would aim for. The internal should be single-glazed, not double, for reasons of thermal necessity, cost, and inherent flexibility of delicate timber sections.

On the matter of overhauling the existing steel frames, you could do a lot of this preparation work yourself (wire-brushing and the like) before passing them on to a galvanizing company.
This is assuming that the frames are indeed redeemable, something one can’t take for granted – especially if your house is near the coast where salty air would disrupt the process of passive oxide fim formation on the steel.

Could you gingerly take out one typical window, strip out a pane or two of glass, examine the grooves and edges ? Then maybe you could post on to this thread some photos, preferably including a ruler in the photos so we can judge the dimensions.

The windows are in lovely condition. A local handyman stripped down the french windows to the steel and repainted them, at vast cost in time and health (he used high solvent paint that nearly killed me and took ages about it); they weren’t closing well then but now are. And a local locksmith took out the lock, brought it home and lovingly took it to pieces, oiled and renovated it, so it even has the original lock. Before that, they were kind of bulging and hard to close – but Crittall advised me that this was just successive layers of paint since the 1930s, and so it proved.

Not steel windows but wooden sash restoration
http://www.lambstongue.ie/journal/