Period Secondary glazing dilemma. Please help.

[another_richard]

Victoria 1880s terrace down 'ere in Hastings not listed.

Last 6 of about 100 houses in the road to still have wooden sashes.

All sashes are 2 over two. House is ex-rental so lots of the original glass has been 'removed', lack of putty means more rattles than a Alberta bush.

Window by window I plan to fit secondary glazing.

In a fit of pique I bought wood 70mm x 34mm for the frame and 25mm x 18mm for the beading.

I plan to essentially create a frame (1520mm x 1080mm) using the wood and purchase x 4 (4-6-4) double glazed windows to slot in (£60 for four panes).

My dilemma is time - We have a bearn 1.5 years old and he commands all of my attention when I am with him. My wife is doing a PHd and so the time I have him she studies.

Time is very limited.

Me:

I left school many moons ago and I did a C&G in carpentry but have not really picked up the tools in years, instead as an archaeologist I now do CAD and GIS. So using my very old skills I had grand plans to rout nice edges, create mortice and tenon joints sash clamp them together etc but no, orders from 'she who must be obeyed' says get it done in as little time as possible.

So instead of the joints etc I thought of two screws and a splash of glue. Given that each single dg unit (approx 65cm x 45cm) will weigh a considerable amount 7 things became apparent before I start:

1 Will the screws hold the finished frame/panes together?

2 Will I be able to easily lift the window out once Spring comes?

3 I did plan the magnet acrylic plastic sheet route. Although a favourite with my wife I feel x 4 dg units at a total cost of around £60 was comparable to 4mm sheet of plastic at around £40+ I am guessing I cannot use the magnet strip to hold this in place and will have to use screws? Sounds like a silly question but I'll add it anyway.

4 Should the bottom two dg panes be toughened = way out of my price range? Base of window is less than 90cm high from floor level.

5 Can I just squirt low modulus silicone into the frame and insert the dg pane then seal again with the silicone and apply the beading? Or will it require glazing strips and/or lms?

6 The distance from the parting bead on the sash to the ogee architrave is about 60mm so the secondary glazing will stick out a bit. I can live with that but does the gap between my new frame and the sash have to be a minimum distance to improve sound/heat insulation?

7 On each of the 4 panes should I leave a little trickle vent. I would essentially drill a 2mm hole under the beading. Am I on the right lines and/or is this required?)

One final note: My plan was to insert new dg panes into the existing sash by routing out from the inside this would essentially make the window triple glazed. But, given the weight of the new dg units I feel the existing sash could not take the weight. Is this correct?

Thanks for your time.

another_richard.

 

[worms]

So instead of the joints etc I thought of two screws and a splash of glue.

How about surface mounted "T" or "L" shaped brackets as appropriate to the joint?

But it all sounds a fairly heavy-weight approach to the problem!

 

[AMc]

We have a bearn 1.5 years old and he commands all of my attention when I am with him.

4 Should the bottom two dg panes be toughened = way out of my price range? Base of window is less than 90cm high from floor level.

The glass should be toughened - you will never be able to forgive yourself if there is an accident. Complying with regs is also sensible but less significant IMHO.

Toughened units shouldn't be massively more expensive than untoughened - IIRC then it added about 30% to the cost of the glass in my single glazed porch which would be less than 30% of the cost of a DG unit. The difference in cost for my double glazed units wasn't apparent as you must use toughened for a roof. When we broke a unit installing it in the roof it was VERY obvious why it needed to be toughened not standard float.

If the units are much more expensive are then chances are your glazier can't do the toughening and is subbing it out to another company.
My glazier subbed all my DG units to another one because they weren't able to do soft coat Planitherm glass which I was insisting on. Ironically their subbed work still worked out substantially cheaper than the direct quote from the company who did the manufacturing whom I'd also contacted.
If you think you can't afford it then ring around some more companies.

5 Can I just squirt low modulus silicone into the frame and insert the dg pane then seal again with the silicone and apply the beading? Or will it require glazing strips and/or lms?

Don't use any old sealant for DG units or you can cause the seals to fail and the units to mist in no time.
I had some fairly heated discussions with my builders about using cheap sealant "to save a few quid" which would compromise a few thousand pounds of units!
I was recommended to use LN7 as it doesn't react and if you can get your units to come with taped edges then I would do that too.

My new windows were dry glazed with glazing tape on the inside, the DG unit inserted and then beading pinned in place in front.

You should be able to lift DG units 65x40cm without too much trouble - you may want to pick up some glass lifters to give you a really good handle on them (pun intended) I picked up a pair for about £10 from screwfix.

I don't have trickle vents on the secondary glazing that I had installed so I suspect they aren't mandatory but if problems with condensation or damp start to show up you can make them in a wood frame very simply.

I'd question the need to add double glazed units as secondary glazing unless you've already exhausted all other energy efficiency improvements in the room.
I have a mixture of small gap DG sashes, 16mm soft coat DG and some original single glazed windows with single glazed secondary units in powder coated aluminium. The single glazed secondary units are from Everest and they weren't cheap but a well made DIY solution should be just as effective. they cut noise noticeably and the reduction in draughts makes those rooms as warm as the ones with replacement windows.

I also got a quote from http://secondaryglazing.com/ for self fit which might be worth a try for an unobtrusive permanent solution.

There is a thread or two around here about secondary glazing and I would take a look at some of the excellent solutions posters on here have come up with.

 

[88v8]

1 Will the screws hold the finished frame/panes together?
Yes, when it's attached to the frame, no when you lift it out, the whole thing will distort
2 Will I be able to easily lift the window out once Spring comes?
Try lifting the four units together before you fit it. I suspect it may be too heavy to lift out as one
3 I did plan the magnet acrylic plastic sheet route. Although a favourite with my wife I feel x 4 dg units at a total cost of around £60 was comparable to 4mm sheet of plastic at around £40+ I am guessing I cannot use the magnet strip to hold this in place and will have to use screws? Sounds like a silly question but I'll add it anyway.
The magnet strip would be fine for acrylic, but of course it will not insulate as well as a dg unit, also acrylic will pick up scratches in time.
4 Should the bottom two dg panes be toughened = way out of my price range? Base of window is less than 90cm high from floor level.
The existing glass isn't toughened is it... so No. The glass in small dg units is very hard to break, due to the air cushion.
5 Can I just squirt low modulus silicone into the frame and insert the dg pane then seal again with the silicone and apply the beading? Or will it require glazing strips and/or lms?
So you're trying to create an air seal between the dg unit and the existing glass? Changes in air pressure will scupper that, moisture will get in, mould... However if you plan to take it down in the summer that doesn't matter. Just a decent rubber or foam seal will be quite sufficient to make a noticeable difference. This self-expanding seal is perhaps the best.
http://www.affixit.co.uk/industrial-tapes-expanding-foam-tape-c-2_57
It will take up significant variations in gap, and is water-proof, it sticks only to one surface. I've used it on my classic car.
6 The distance from the parting bead on the sash to the ogee architrave is about 60mm so the secondary glazing will stick out a bit. I can live with that but does the gap between my new frame and the sash have to be a minimum distance to improve sound/heat insulation?
Heat, min 0.5", but max 1" or you'll get convection currents between the panes. Noise, ideally about 4". So, it's a trade-off. But the dg units will do the heat, won't they, so all you need to worry about is noise.
7 On each of the 4 panes should I leave a little trickle vent. I would essentially drill a 2mm hole under the beading. Am I on the right lines and/or is this required?)
Not required. You ain't gonna make it airtight....
One final note: My plan was to insert new dg panes into the existing sash by routing out from the inside this would essentially make the window triple glazed. But, given the weight of the new dg units I feel the existing sash could not take the weight. Is this correct?
Correct, You'd have to change the balance weights, and you couldn't get enough weights inside the sash box to provide the balance. For dg units alone, I had to cast my own lead sash weights, because the cast-iron weights at the required weight were too long. Also, you'd get air leaks between the original glazing and the dg units, misting, mould.

I triple-glazed my existing casements, by adding timber to increase the depth of the frame, then inserting hinged secondary frames made of solid brass U-section, with dg units. A lip seal does a pretty good job of keeping the dust out, and they're above radiators so they're in dry air and don't mist. But it took literally weeks of work....
Whatever you do now, perhaps you could look on it as a disposable nappy, to be revisited when you have more time. Meanwhile, if you put up net curtains you wouldn't be bothered by any aesthetic deficiencies ....

Ivor