Double glazing old wooden frame

[svouts]

Hi, I have a house with wooden single-glazed windows. There are 25 windows with cross sections, each with 4-6 glass panels. I would like to replace the glass panels with double glazing, which totals 130 glass panels (each measuring 36x45 cm). Currently, the windows have 4mm single-glazed glass, and I can measure an extra space of 14mm to the edge of the frame. It seems there is a single rebate of 18mm.
I have two questions:
1. is there double glazing thin enough to fit into an 18mm single rebate?
2. If the cost is too high to replace all the windows, which floor loses the most heat, and should I prioritize double glazing on that floor?

Many thanks for the advice!

 

[cross thread]

Have you considered secondary glazing

 

[endecotp]

Is it a listed building, or in a conservation area?

You can get slimline double glazed units that are 12mm thick, or you can get vacuum units that are even thinner. Both options are expensive, as is the work to fit them in the existing frames.

 

[svouts]

Secondary glazing is not an option for most of the windows, except for the small ones. Also in the garden there are french doors and again no secondary glazing can be installed.

 

[svouts]

Is it a listed building, or in a conservation area?

You can get slimline double glazed units that are 12mm thick, or you can get vacuum units that are even thinner. Both options are expensive, as is the work to fit them in the existing frames.

I have checked and vacuum units are very expensive. At least 3 times more expensive.

Though I found double glazing in good value that has 4mm glass panels and 6mm gap in between. In total 14 mm thickness. They claim an insulation value of 2.0 W/m2 K (HR).
Would it be good solution?

 

[svouts]

Is 14mm double glazing possible to fit in 18mm frame? what is the best option to fit it?

 

[jj4091]

4-6-4 AFAIK is the basic standard for double glazed units. you might be best asking your local glazing company to do an on site visit and advise on what would be best for your windows and wallet.

 

[endecotp]

You can get units as thin as 3+4+3 mm. They are of course less insulating than thicker units.

Search the web for examples. I'm not going to link to any because I can't vouch for any of the companies.

The cost of vacuum units looks less extreme when you include the fitting costs and allow for their much better insulation - and especially if you remember that a few years ago their cost was even more extraordinary!

I don't know what the maximum unit thickness that will fit in an 18mm rebate is. It is possible to router the rebate to increase its depth. I don't know how often this is actually done.

 

[crank39]

You also need to factor in the start of replacements in a few years time too because as a general rule double glazed units do not like timber windows

 

[ronniecabers]

Slimline sealed units generally are 4mm glass, 4mm spacer , 4mm glass, so 12mm overall but do seem to carry a surcharge and as a general rule don't actually seem to last as long . Normally double glazed sealed units will have spacer bar sizes from 6mm up to 20mm , going up at increments of 2 ( actually it's 5.5mm up to 19.5mm but we won't go into that lol ). Potentialy 12 or 14mm units will fit in the existing rebates depending on the beading you are using. Another option is actually to have ' stepped 'units , where the outer pane fits into the normal glazing rebate , then the internal pane is slightly smaller all the way round and fits completely inside the internal rebate, which potentially means you can have thicker sealed units, does mean however that visible glass size is reduced by approx 50mm in each direction. Hope that made sense.
As Crank says though, generally sealed units don't last as long in wood and a lot of manufacturers won't warranty them if they are going into wood or only offer a shorter warranty period

 

[svouts]

You also need to factor in the start of replacements in a few years time too because as a general rule double glazed units do not like timber windows

Many thanks for the comment i had no idea, what is actually the problem?

 

[crank39]

Lack of water drainage, timber windows generally don't have any built in drainage like upvc section does, if water builds up behind the putty or beads and in any way touches the bonding seal of the unit even over a short period of time will fail the seal and the unit will steam up

 

[endecotp]

You can get slimline units that are sealed with epoxy, which are supposed to be more water-resistant than conventional seals and therefore better in timber frames. I see one supplier offering a 10 year guarantee on these. Of course they cost more!

(Full disclosure; I have no practical experience of any of this. I also live in a house with more than 100 single-glazed panes, smaller than yours. I have secondary-glazed all the bedrooms, and plan to fit slimline double-glazed units of some sort in the living room and kitchen eventually. I’ve read a lot about the subject but have yet to “bite the bullet”. One neighbour had slimline DG units in new sashes installed a couple of years ago; they had lots of issues with the quality of the installation but no problems so far with the units themselves. Also I recently met a retired quantity surveyor who told me that he had just fitted vacuum units to all his windows; he was very enthusiastic about them.)