Double Glazing and repairing windows

[Theo]

We live in a rather nice listed (grade 2) building and need to repair all of the windows. The built in frames are in good enough condition to keep but the casements have rotted and need complete replacement. Much of the glass is cracked. What we would like to do is to get a local carpenter to build new casements for us and glaze them with sealed double glazing units. We have found some with a really thin border so the glazing bars will not end up very much thicker than at present.

When we applied to the planning officer for listed building consent he sent a letter back saying that if we are repairing the windows then we do not need listed building consent but double glazing is out of he question. Without double glazing the condensation problem that we have will continue and the new casements will rot. The planning officer said that secondary DG would be all right but this cannot be fitted to the downstairs windows because of the shutters

Has anyone got any ideas as to how we can legally fit double glazing?

All the best

Nick

 

[Flyfisher]

A true repair, i.e. exactly 'like-for-like', does not need Listed Building Consent but fitting double glazing units where none previously existing would clearly not qualify as such. So, the only legal way to fit DG is to obtain LBC. However, it is extremely unlikely that this would be granted, as you have already discovered.

The main issue with DG units in traditional windows revolves around the changes necessary to the original dimensions of the window, usually the thickness of the glazing bars. As you've already admitted, your proposed solution would result in thicker glazing bars and this can have a detrimental effect to the overall appearance of the window. Hence, I presume, the objection of your historic buildings officer.

Have you read this thread? http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=9855&p=113154&hilit=glazing#p113154
There's a reference in there to Richard Smith at Old Manor Cottages who claims to be able to make DG casement windows with very narrow glazing bars that have been approved by many conservation officers across the country. I've no idea how effective they are (possible long-term issues with the DG unit seals?) but I've seen them and they look pretty good.

You mention shutters; do these actually work? If so, they should greatly help the insulation, and might be just as good as DG anyway, though admittedly not so convenient during the daytime.

 

[AMc]

We have shutters on some (replacement double glazed windows), they do a grand job of insulating when closed but obviously it's a bit dark during the day. Another thing I discovered is that on one seldom used window in a cooler room there has been some condensation on the window which has grown mould. Not a rotting problem, but a reminder that I need to open the shutters now and again to let the moisture evapourate.

When I was looking I found this site - I have absolutely no experience of them but one of the glaziers I spoke to mentioned they were effective & expensive
http://www.sashglass.co.uk/

On our original windows I've decided to go with secondary glazing but that's because the windows don't need to be repaired, just painted.

I also picked up a link to these people - http://www.magneglaze.co.uk/website/index.htm - probably from here which might be helpful.

 

[biffvernon]

Without double glazing the condensation problem that we have will continue and the new casements will rot.

Welcome to the forum, Theo. You've got a common problem and there probably isn't going to be an answer that you like. Your rotting casement arguement is poor. Make sure the new casements are a moderately durable softwood such as larch, Douglas fir, western red cedar or Scott's pine and are painted with real linseed oil paint. Or, better still, use oak. They will not rot in your lifetime and in the case of oak not in your grandchildren's lifetime.

Don't dismiss the secondary glazing route too quickly. Would it be possible to post a photo taken from indoors to show the relationship between shutter and window. Sometimes there is a solution beyond thick curtains and woolly underwear.

 

[Pford75]

Welcome to the forum.

I would agree with Biff (who knows a whole lot more about wood than most) that if you choose the right timber, you should have no cause for concern in the foreseeable future.

I would also add that double glazing is not an indefinite, maintenance free solution. Sealed units have been known to fail as quickly as 5 years, but with many showing signs of misting etc after 10yrs...so you may find that replacement oak windows are cheaper and more durable in the long run.

 

[Smithy]

I agree with the info already posted with regards to th single glazing and the impact that double glazed units due to increased glazing bars may have on Listed and/or historic buildings. Has anyone read the study undertaken by Historic Scotland. I have attached a link;

http://www.historic-scotland.gov.uk/thermal-windows.pdf

In summary, secondary glazing and secondary glazing with curtains has a lower U-value than that of double glazed units. Shutters alone is only marginally higher. Subject to impact/LBC, insulated shutters again offer a lower u-value that that of dg units.

 

[Lime]

Welcome to the forum Theo.
I'm not convinced that the casements need to be completely replaced, nearly all that I have ever seen can be repaired in some form.
Perhaps you are looking at them for an opportunity to put in double glazing without considering how long they have lasted and how much they contribute to the appearance of your rather nice listed (grade 2) building?

Also fitting a double glazed unit in a sash frame that only had single glass is difficult.
Apart from the extra thickness needed to fit the extra pane of glass the weights in the old frame have to be larger too.
Usually space is very limited in older frames.

Secondary glazing works well without spoiling the external appearance of the windows.
You'd also be able to keep some of the old glass if you're careful which is very much part of the "rather nice" of the building.

 

[Penners]

Of course, secondary glazing doesn't have to be permanently fitted. You can create a fairly effective secondary glazing system using plastic beading and clips, which is just clipped into place when the cold weather comes, and removed in the spring. The glazing itself can be glass or acrylic sheet.

I have a family member who uses this system, and it's satisfactorily un-noticeable in use. I would say that it's no more unsightly than many other forms of secondary glazing, and less so than some.

http://www.easyfixsecondaryglazingkit.co.uk/

 

[Moo]

Bless you for that, Penners.
In spite of being in a terrace, with very thick walls fore and aft, the size of our windows is making the whole house feel very chilly. Multiple layers of wool keep the body warm but I really do draw the line at wearing gloves or mittens indoors so I've been giving serious thought to secondary double glazing, but have been put off by the cost of having it made and installed. That system looks just the job - though I'm wondering whether I could do it even more economically by losing the (very visible) plastic sleeving and just fixing acrylic sheet with those staple thingies one uses for clipping wires along the skirting board (they come in a dark brown that would be invisible on our windows).
Any thoughts?

 

[Penners]

Moo, the problem is that the plastic edging is what creates a passable seal against the window frame. And the seal is what traps the insulating air. Did you scroll down the Easyfix page and see that the edging comes is white, brown (yuck) and clear?

Why not give one room the treatment and see whether you feel you can live with it? And, of course, whether you can doff the gloves and thermals?

Anyone with shares in D*mart, be warned!

 

[Pford75]

Could you perhaps substitute the plastic beading with some double sided sticky insulation tape? This could be stuck to the acrylic and then to the frame? It comes in rolls from the local DIY shed

 

[Moo]

I'm a bit wary of using adhesives, having seen what even masking tape can do to paintwork. If the plastic beading is not too obtrusive, I'd rather have something that could be removed and replaced just leaving the little holes made by the clips (which could even be left in place if they're the right colour).

 

[Penners]

The other consideration, of course, is the clips. They're designed to secure a certain thickness of beading, over a certain thickness of glass/acrylic. If you vary this too much, the clips might (a) not press the stuff to the window frame hard enough to create a seal, or (b) not be able fit over it.

 

[Flyfisher]

Not that I'm anywhere near this sort of 'finishing touch' yet, but I've thought about making secondary DG units by using a wooden frame to hold the secondary glazing (perhaps a DG unit itself?), fixing some sponge rubber draft-excluder around the frame and then screwing the whole assembly onto the existing window frame, which would compress the draft excluder and make a good seal between the original window glass and the secondary unit.

Come springtime and the whole unit could be removed and wouldn't leave any visible traces except a few screw holes, which could be easily capped with something to match the original window frame.

 

[biffvernon]

I've thought about making secondary DG units by using a wooden frame to hold the secondary glazing (perhaps a DG unit itself?), fixing some sponge rubber draft-excluder around the frame and then screwing the whole assembly onto the existing window frame, which would compress the draft excluder and make a good seal between the original window glass and the secondary unit.

I've done exactly that, making the frame from quite slim sections of oak and toughened glass and E-section draught excluder.

 

[DaveBrigg]

I've taken a quicker, less skilled (and lazier) route and screwd the acrylic directly to the frame, with the draught excluder stuck to the acrylic to make a seal. It works well with thicker acrylic, but for thinner pieces over a square metre there has been a little warping, which a wooden frame would have prevented. When removed, the screw holes are not too noticeable, but we got so used to the lack of draughts and reduction in noise that most of it remained in place over the summer.

 

[Cloudscape]

This stuff was mentioned in another thread http://www.magneglaze.co.uk/website/idea.htm

There are other makes available.

 

[Penners]

I've thought about making secondary DG units by using a wooden frame to hold the secondary glazing (perhaps a DG unit itself?), fixing some sponge rubber draft-excluder around the frame and then screwing the whole assembly onto the existing window frame

Sounds a perfectly effective solution, provided you have somewhere to store the secondary glazing sheets during the summer.

 

[Penners]

This stuff was mentioned in another thread http://www.magneglaze.co.uk/website/idea.htm

I think I can see two possible disadvantages to that system. Firstly, I imagine that the strips stuck to the window frame (not sure whether it's the steel or the magnet) would be rather unsightly when the secondary window is removed. Secondly, £100 - £120 per m^2!!

 

[Lime]

I've thought about making secondary DG units by using a wooden frame to hold the secondary glazing (perhaps a DG unit itself?), fixing some sponge rubber draft-excluder around the frame and then screwing the whole assembly onto the existing window frame

Sounds a perfectly effective solution, provided you have somewhere to store the secondary glazing sheets during the summer.

Storage is a problem particularly for very large pieces.
As has been said previously by someone else, when I used secondary glazing years ago it was left on in summer as it also kept the heat and noise out.
The only reason I removed a piece was to open the window or to allow some ventilation for the enclosed space.
Some windows suffered condensation more than others.