Adding double glazed units to original sash windows
Discussion
I did a search and while this has been discussed, it was a while ago and most of the threads are just arguments about wood vs UPVC!
We have lovely large original Edwardian sash windows which are in reasonable condition but we are considering getting them refurbed with draught strips etc and also considering getting them to replace the single glazing with slimline double glazing (believe the product is called Slimlite). Has anybody had this done and can share your experience of this?
I'm not sure that we can make a case based on the energy savings alone (though the windows are massive and there's lots of them), but I think the reduction in condensation and improvement in thermal comfort will make it just about justifiable, plus we plan to be here for a long time and this will be part of a major plan of thermal and fabric upgrades. I note that they can even make the glass look mottled to match the old style glazing, which would be good.
Keen to hear any experiences, and if you're in Kent, some recommendations (or warnings) would be good!
We have lovely large original Edwardian sash windows which are in reasonable condition but we are considering getting them refurbed with draught strips etc and also considering getting them to replace the single glazing with slimline double glazing (believe the product is called Slimlite). Has anybody had this done and can share your experience of this?
I'm not sure that we can make a case based on the energy savings alone (though the windows are massive and there's lots of them), but I think the reduction in condensation and improvement in thermal comfort will make it just about justifiable, plus we plan to be here for a long time and this will be part of a major plan of thermal and fabric upgrades. I note that they can even make the glass look mottled to match the old style glazing, which would be good.
Keen to hear any experiences, and if you're in Kent, some recommendations (or warnings) would be good!
We had this done in 2017 and it made a significant difference to the warmth and draughty-ness of the windows. The only ongoing issue we have encountered is that they never balanced the weights correctly so one or two of the windows don't stay partially open, they are either fully open or fully closed. Back then it was about £900 a section IIRC.
Simon
Simon
V8 Animal said:
Slim lite units have no warranty and are expensive, don’t last long before they fail. Also extra weight on the sashes.
They do have warranty, I suspect longevity problems would be people bedding them into linseed-oil putty, which destroys the edge seal of the unit. I've replaced about 50 sealed units at home because the fitters did exactly that.Butyl putty is the right answer - https://www.reddiseals.com/product/hodgson-glazing...
The detailing they show in their brochure isn't fantastic, but it's as good as you'll get in an original window. The unit is in contact with the frame all round, and there's no drainage, so any water that does get in will get caught between the frame and unit. Unfortunately, the size of the rebates mean there's no other option - they recommend repainting every 3 years to maintain the seal.
The sashes can be rebalanced, I'd expect them to redo the sash cords, check the pulleys and rebalance if they were reglazing.
https://www.sashglass.co.uk/media/slimlite-brochur...
If you look at a modern window, the sealed unit has a gap all round, drainage built into the frame, dry-glazed with gaskets, and no putty in sight. But you can't do that with a traditional sash window.
I've done a few of these in the past, horrible, fiddly, time consuming jobs! I've even got a packet of the seals still kicking about somewhere.
Mighton is one of the sites to go to and you'll need replace the weights, lead was the thing back then, I don't know if it's changed.
You could have just new sashes made to take the DGUs.
You need to weigh every sash when it's done.
We used 4/6/4 units.
Mighton is one of the sites to go to and you'll need replace the weights, lead was the thing back then, I don't know if it's changed.
You could have just new sashes made to take the DGUs.
You need to weigh every sash when it's done.
We used 4/6/4 units.
Edited by Evoluzione on Tuesday 31st January 18:17
shtu said:
They do have warranty, I suspect longevity problems would be people bedding them into linseed-oil putty, which destroys the edge seal of the unit. I've replaced about 50 sealed units at home because the fitters did exactly that.
Butyl putty is the right answer - https://www.reddiseals.com/product/hodgson-glazing...
The detailing they show in their brochure isn't fantastic, but it's as good as you'll get in an original window. The unit is in contact with the frame all round, and there's no drainage, so any water that does get in will get caught between the frame and unit. Unfortunately, the size of the rebates mean there's no other option - they recommend repainting every 3 years to maintain the seal.
The sashes can be rebalanced, I'd expect them to redo the sash cords, check the pulleys and rebalance if they were reglazing.
https://www.sashglass.co.uk/media/slimlite-brochur...
If you look at a modern window, the sealed unit has a gap all round, drainage built into the frame, dry-glazed with gaskets, and no putty in sight. But you can't do that with a traditional sash window.
I would like to see that warranty!Butyl putty is the right answer - https://www.reddiseals.com/product/hodgson-glazing...
The detailing they show in their brochure isn't fantastic, but it's as good as you'll get in an original window. The unit is in contact with the frame all round, and there's no drainage, so any water that does get in will get caught between the frame and unit. Unfortunately, the size of the rebates mean there's no other option - they recommend repainting every 3 years to maintain the seal.
The sashes can be rebalanced, I'd expect them to redo the sash cords, check the pulleys and rebalance if they were reglazing.
https://www.sashglass.co.uk/media/slimlite-brochur...
If you look at a modern window, the sealed unit has a gap all round, drainage built into the frame, dry-glazed with gaskets, and no putty in sight. But you can't do that with a traditional sash window.
Problem is the shoulder height not enough sealant due to rebate heights.
I’ve never seen a warranty, been in the trade all my life.
Only ever seen them glazed in silicone.
Agreed linseed oil putty is a no no.
Hodgsens heal and bead system doesn’t work with heritage windows due to slim glazing bars.
We have had it done on most of ours; original 100 year old sashes. I don’t think it has helped at all with condensation or noise. The draught proofing works fine of course.
I recently saw some Accoya windows made locally for a price I was stunned by in a good way, so will likely replace slowly but surely rather than doing any more slimline.
I also think the slimlines were bedded in linseed given how much the birds ate of it.
I recently saw some Accoya windows made locally for a price I was stunned by in a good way, so will likely replace slowly but surely rather than doing any more slimline.
I also think the slimlines were bedded in linseed given how much the birds ate of it.
When we lived in a conservation area in a Hertfordshire town 25+ years ago we found a Heritage Sash Glazing company in North London? - they came and renovated the sashes, installing two panes of differing thickness into each light, as well as a built-in draught excluding system into each sash so that the windows were virtually sound-proof, unless open. Amazing quality work, and all within one working day, including painting. You could open and close the moving sash with just a couple of fingers, but they sealed to the frame perfectly. Can’t remember the outfit’s name, sorry.
This is the sort of company I would seek out - do it once, do it right
This is the sort of company I would seek out - do it once, do it right
simon_harris said:
We had this done in 2017 and it made a significant difference to the warmth and draughty-ness of the windows. The only ongoing issue we have encountered is that they never balanced the weights correctly so one or two of the windows don't stay partially open, they are either fully open or fully closed. Back then it was about £900 a section IIRC.
Simon
Thanks, did you notice a significant reduction in condensation?Simon
CoolHands said:
I would just replace completely with REHAU Heritage sliding sash windows, that’s what I did. But you’ve probably already made up your mind.
I told you it would end up with an argument about UPVC 
On any other house I would certainly be considering this - but this house is a bit unique in that the previous owner has gone to a truly exceptional extent to preserve and re-instate the original Edwardian features, and the windows are in otherwise good condition.
Arranguez said:
We have had it done on most of ours; original 100 year old sashes. I don’t think it has helped at all with condensation or noise. The draught proofing works fine of course.
I recently saw some Accoya windows made locally for a price I was stunned by in a good way, so will likely replace slowly but surely rather than doing any more slimline.
I also think the slimlines were bedded in linseed given how much the birds ate of it.
That's interesting - the condensation issue is one of the reasons for doing this (over just getting them draught proofed - how long ago did you do it, out of interest? I recently saw some Accoya windows made locally for a price I was stunned by in a good way, so will likely replace slowly but surely rather than doing any more slimline.
I also think the slimlines were bedded in linseed given how much the birds ate of it.
V8 Animal said:
Cow Corner said:
That's interesting - the condensation issue is one of the reasons for doing this (over just getting them draught proofed - how long ago did you do it, out of interest?
Secondary is the best option.I agree it’s the simplest and cheapest, but for reasons explained above, it’s not an option I’m considering.
I’m a Building Surveyor so understand the options, my question was specifically asking for practical experiences of those who have done it.
Arranguez said:
The last ones we did were two years ago in our bedroom and ensuite. Still get loads of condensation on all of the slimline units aside from the ones in the dining room with a radiator underneath.
Very interesting, thanks. Do you know the spec of the units you have (I.e. thickness of glazing and cavity)?Clearly some more research to be done - they’re quite niche, so haven’t actually spec’d any before for anyone else!
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