Double glazing in Listed Building

[paulb33]

Hi All,

We're very lucky to live in a lovely Grade II Listed 1901 building. The former home of John Coates Carter, a reasonably celebrated architect. The interior is pretty much intact with many lovely arts & crafs and art nouveau features. BUT....weep.....many of the windows were replaced with uPVC in the 90s.

Here's our dilemma. We clearly benefit from the noise and thermal transmission benefits. And, environmental concerns surely must be considered. Is there yet a satisfactory timber double glazed unit on the market?

First glances at a few of the big players' products (Box Sash and Mumford) suggests not. For a start, I don't like the timber beading used to fix the unit in place. But, there surely must be a market for a more specialised solutions? Perhaps a narrower gap DG unit with special gas, which might be a suitable compromise between look and function? Perhaps using 'greenhouse glass' type glazing? Or, is this just wishful thinking?

We have some original windows to work from and the glazing bars are chunky (27mm wide). This will hide some of the unit. Most windows are side opening casements. Oh, and we have 33 to replace.....

Value folks' thoughts.

Regs.

Paul

 

[Moo]

The words "Vernon" and "Biff" spring to mind .......

 

[paulb33]

Gulp. Be gentle with me....please......

 

[MdB]

http://www.biffvernon.freeserve.co.uk/intro.htm

 

[Flyfisher]

As far as practicality is concerned, a lot will depend on the style of the windows (and I've no doubt Biff could advise on this). You mention that the original glazing bars are 27mm and that will certainly help with DG units, but it would certainly help if you could post some photos of the original windows.

However, it may not be such a simple case of replacing uPVC with wood.
When was the house listed and were the original windows double or single-glazed? I'm not sure if, technically, you would need LBC to replace an illegally installed window (assuming the house was listed before the uPVC was installed), but I certainly would not embark on replacing 33 windows without talking with the relevant CO because you'll risk replacing one unacceptable window with another unacceptable window - even if it was wooden.

If the original windows were single-glazed, you may not be granted LBC to replace the DG uPVC windows with wooden DG windows.

Have you been in contact with your CO?

 

[paulb33]

Ah, yes. Biff and I corresponded in the past. Thank you. I've just PM'd him once more.

Any other developments in this area? Thoughts on going from uPVC to DG? Should I be going single glazed?

P

 

[Roger H]

Hi. I'd definitely go for doubleglazing. Slimlite glazing goes as thin as 4mm glass, 3mm space, 4mm glass. Units can be puttied in so no external beading required.

 

[paulb33]

As far as practicality is concerned, a lot will depend on the style of the windows. You mention that the original glazing bars are 27mm and that will certainly help but it would help if you could post some photos of the original windows.

When was the house listed and were the original windows double or single-glazed? I'm not sure if, technically, you would need LBC to replace an illegally installed window (assuming the house was listed before the uPVC was installed), but I certainly would not embark on replacing 33 windows without talking with the relevant CO.

If the original windows were single-glazed, you may not be granted LBC to replace the DG uPVC windows with wooden DG windows.

Have you been in contact with your CO?

I've attached some awful Blackberry photos of an original window and the garden side of the house... (I' take responsibility for the plastic in the garden....)

The arched, stained glass, feature windows are all intact, mercifully. There are some nicer photos on Flickr of the road (services) side of the Red House, Penarth....search for "Coates Carter Penarth" and my house is among a number of his local examples.

The house was hurriedly listed AFTER the uPVC went in. Listed building consent is now needed to change the uPVC (!). The CO has been very supportive....and pragmatic. I suspect that well done DG wooden units would be welcomed. But, I haven't contacted the CO for a few years about it.

Thanks for your interest. I've PM'd Biff, who was a wealth of advice and support some five years or so ago. Three children and a relo to USA had put this all on hold until now.

Paul

 

[Flyfisher]

The house was hurriedly listed AFTER the uPVC went in. Listed building consent is now needed to change the uPVC (!). The CO has been very supportive....and pragmatic. I suspect that well done DG wooden units would be welcomed. But, I haven't contacted the CO for a few years about it.

Ah, that changes things then. I guess it was hurriedly listed to prevent any more atrocities being inflicted on the poor house.

Yes, LBC will be required to change the uPVC windows but I'm not surprised the CO is supportive. I would approach things by coming up with sympathetic designs for new wooden DG windows and then presenting them to the CO. If the CO is happy (and if not they should be able to suggest a suitable alternative design) then the LBC process should be very straighforward.

 

[paulb33]

Thanks again. I'm likely to need some drawings done. Any thoughts on getting the ball rolling, getting quotes etc? Need to contain costs, but are we in the realm of a conservation architect here? Need to do it right, but avoid going OTT...
Paul

 

[Roger H]

That's a great shame for the building Paul but at least you are doing the right thing. You can thank George Osborne for scapping the VAT exemption on LBC works which would have saved you 20% on your new windows. Change comes in Oct 1st 2012 so no way of squeezing in an application now alas.

 

[Flyfisher]

Thanks again. I'm likely to need some drawings done. Any thoughts on getting the ball rolling, getting quotes etc? Need to contain costs, but are we in the realm of a conservation architect here? Need to do it right, but avoid going OTT...
Paul

The drawings I've used for LBC submissions for new windows were produced by the company making the windows. I would approach your preferred manufacturer and discuss the problem with them. Anyone capable of such work should appreciate the LBC process and be able to assist with the required drawings.

 

[paulb33]

Wot?! No LBC VAT exemption any longer? I leave the country for a few years...

So, I don't get the saving if I squeek the LBC application in before Oct 1st? Ugh :!:

 

[biffvernon]

I'm getting mentioned far too often in this thread, and I'm far too busy building my own conservatory at the moment to make other people's windows. There really ought to be more people making decent oak windows - there's a market out there but the Great British Unemployed don't seem to have noticed. It's perfectly possible to have oak windows with 30mm glazing bars supporting 4-16-4 dg units. The difficulty is finding a joiner prepared to use oak. They all seem to think it's a difficult material to use, hard to obtain and expensive, none of which is true.

For what it's worth, I'd be very suspicious of the 'slimlite' and other units that are less than 24mm thick.

 

[paulb33]

Thanks again, Biff. I'm in the wrong business, clearly! :roll:

My search continues...

Paul

 

[paulb33]

It's perfectly possible to have oak windows with 30mm glazing bars supporting 4-16-4 dg units.

Encouraged to learn that the glazing bar would work. But, doesn't a 16 gap reveal more black plastic? Can the rubber seal spacers be hidden?

Paul

 

[AMc]

We're not listed. We have a lot of 1990s double glazed sashes 6 over 6 which are made from individual units and consequently have thicker glazing bars than the original 8 over 8. They are made from softwood with spring sashes rather than weights and pullies. Many of the units have failed as sunlight deteriorates the seals and there are lots of them.

During our renovation we had a 70s casement replaced with a faux sash (fire escape regs) We fitted a single larger unit with glazing spacers at the same point as plant on wooden bars. This removes the two mesh effect of plant ons in front and behind with an open unit in the middle.
While it's not as thermally efficient it is a compromise that works quite well. There are fewer sealed edges (by many multiples) to fail and they can be recessed into the external parts of the frame without making the window look out of proportion.

I got the joinery company to make the windows and sourced the glazing units myself to get the best price and the best performing product. At the time that was Saint Gobain Planitherm - soft coated low emissivity glass. IIRC they were 4-16-4mm. I should have tried a bit harder to get warm edge spacers but it was a bridge too far for the local glazing suppliers and I didn't want to order from further afield.

Technically anyone installing windows should be FENSA registered which allows them to certify they comply with building regulations (including part L1B for thermal efficiency). In practice any good joinery company should be able to make windows to your design and if you use a manufacturer recommended sealed unit design (with tested U values) you should be able to make most building control officers accept that your design will fall within the tolerances of the regs.

 

[Flyfisher]

A simple web search for 'oak windows' will return loads of companies that offer to make bespoke oak windows (and much more).

Finding a good one may take some time and effort, of course, though any reputable company should be able to provide customer references and, possibly, customers willing to let you see their work.

But isn't that the same when looking for all sorts of quality bespoke items?

 

[paulb33]

I got the joinery company to make the windows and sourced the glazing units myself to get the best price and the best performing product. At the time that was Saint Gobain Planitherm - soft coated low emissivity glass. IIRC they were 4-16-4mm. I should have tried a bit harder to get warm edge spacers but it was a bridge too far for the local glazing suppliers and I didn't want to order from further afield.

Technically anyone installing windows should be FENSA registered which allows them to certify they comply with building regulations (including part L1B for thermal efficiency). In practice any good joinery company should be able to make windows to your design and if you use a manufacturer recommended sealed unit design (with tested U values) you should be able to make most building control officers accept that your design will fall within the tolerances of the regs.

Thanks for your helpful reply. You're inspiring me to take a more hands on approach to this. Who did you get to fix and install the windows? The joinery company or a separate chippy?

 

[paulb33]

A simple web search for 'oak windows' will return loads of companies that offer to make bespoke oak windows (and much more).

Ah: Google. Just had a very pleasant conversation with a local(ish) bespoke oak joinery firm who has experience of slimline DG units. We're meeting at the weekend. Admittedly, he sucked through his teeth when I mentioned slimline units..... Gave me ballpark of £300 per m2 for krypton filled DG units versus £50 for standard. But, he acknowledged that there are more players than Slimline now and he needed to check on current prices... Progress of sorts...

Paul