Building Control Part L - new documents out

[londonman]

The Approved documents regarding the Part L changes coming into force in October make truly depressing reading for anyone with a non-listed period property. My read is that if you are Listed than, provided your local Conservation Officer is strong-willed enough, then it is very much business as usual. If, like me, you live in a period property that is non-listed then getting your windows replaced with bespoke timber-framed units is going to be very expensive - that is if there are any small joinery firms left who will be available to do the work.

To precis....any replacement window (ie replacing the complete unit including the frame) will require either :

• a window with a WER (windows energy rating) certificate of C or better OR
  
  have an overall u-value of 1.6 OR
  
  a central-pane u-value of 1.2 or better.

Getting a WER certificate for a small joinery company is financially out of the question. So let's look at option 2.

For a kick-off, we don't have a level playing field. New builds need only have an overall u-value of 2. So why are existing property owners penalised by having this draconian value of 1.6 thrust on them? I would dearly love for someone to force a judicial review on this.

OK - an overall value of 1.6. You can't meet this with normal double-glazed units. Nor any filled with argon unless you go for very expensive specialist coatings as you need to have a glazing unit with a u-value of around 1.2. You could go krypton fill. I have no idea as to cost on this. Expensive I think. Specialist coatings? Also expensive. I got a quote for £540 + VAT for the specialist dgu's for a 6x6 sash window. That is before the cost of the wood or labour to make it or cost to install it.

You can reduce the cost by going for a single dgu and then putting in ghastly duplex bars or stick-on faux glazing bars. Lovely. Really fits in with the period property ethos.

Or you could triple glaze. That will make your windows about 66mm thick. Now factor in the extra width you'll need in the glazing bars to carry the extra weight...but hang on, the heat loss via the timber is greater than that through the triple glazing units.....

Oh, I forgot. How are you going to convince the Building Control Officer that your windows are 1.6 u-value overall?

Ah..I hear you say...the double-glazing people will have the same problem. Not so. Nor will people like Magnet because they are large enough to pay for their windows to be WER certified.

But...you say..they still will have the problem re expensive double glazing units, won't they. No, they won't. I played around with the WER formula. Take a window with a frame that is 10% of the overall window area. Take a total solar gain of around 0.65 ...a not out-of-the-norm value. Add in a very leaky air leakage of 1 and what overall u-value do you need to achieve to get your C-rating? Why....2.0...which is fairly easily achievable with standard dgu's.

So the uPVC boys are going to have a field day and small joinery companies will go out of business.

 

[Penners]

New builds need only have an overall u-value of 2. So why are existing property owners penalised by having this draconian value of 1.6 thrust on them?

Could it perhaps be due to a perception that period properties are likely to be more thermally conductive elsewhere - walls, roof, etc.? So the more draconian window requirement is supposed to go some way the make up for this?

I suppose the only positive thing that could arise from these new regulations is that period property owners might be more likely to repair original windows than they have been in the past, in order to avoid the cost of having to comply with this more draconian regime.

Or am I whistling in the dark?

 

[biffvernon]

Thanks for bringing this up, Londonman. I'm one small joinery business that won't be going out of business. There are technical problems that have technical solutions and legal problems that have illegal solutions. Between one and the other a way will be found.

We do have a small problem - the planet needs saving. However well intentioned, Part-L does very little to solve that problem.

I do wish folk (and Governments) talked more about Jevon's Paradox. Simply put, if you save money on your heating bill and spend the money saved on jetting off to the Costas, the planet has not benefited. We need carbon rationing not rules about windows.

 

[londonman]

New builds need only have an overall u-value of 2. So why are existing property owners penalised by having this draconian value of 1.6 thrust on them?

Could it perhaps be due to a perception that period properties are likely to be more thermally conductive elsewhere - walls, roof, etc.? So the more draconian window requirement is supposed to go some way the make up for this?

I suppose the only positive thing that could arise from these new regulations is that period property owners might be more likely to repair original windows than they have been in the past, in order to avoid the cost of having to comply with this more draconian regime.

Or am I whistling in the dark?

The one good thing is that if you replace the openers with a double-glazed one and keep the frame then it is outside the scope of Part L.

PS I'd like to keep the thread on-topic and not get hijacked by any discussion on saving the planet, if possible.

 

[Feltwell]

Hmm. Some people like me, with a couple of nasty 1970's casements to replace on the back of the house, might just forget to notify Building Control and may mistakenly put in a window that's not easily distinguishable from the original sashes on the rest of the house......

 

[Flyfisher]

In a few hundred years, historians may look back on the "Part-L" laws that blighted our period properties in the same way that we can look back on those properties blighted by the window tax laws. Perhaps we can take some comfort in the fact that historic properties are products of the times they've existed through and all this part-L nonsense is part of that history, frustrating though it may be.

Meanwhile, as previously noted, it might be difficult if windows are on public facing roads, but there must be thousands of windows that are practically invisible and who would ever know when they were replaced, particularly when replaced like-for-like.

 

[JohnB]

Bending the rules doesn't help when you want to sell. Part of the £10k I knocked off the price I paid for my place was due to lack of a FENSA certificate, and that was just because one wasn't produced for some reason, not that the windows didn't comply. I've got it now!

 

[Penners]

Part of the £10k I knocked off the price I paid for my place was due to lack of a FENSA certificate

Good grief! Your vendors must have been desperate. :shock:

OK, just between the two of us, and with nobody else listening, if they'd told you that they weren't prepared to drop the price, would you have walked away?

 

[Flyfisher]

Yes, I've heard that argument but have never really understood it. If the windows were installed before the Part-L regs were introduced then (I believe) a FENSA certificate is not required.

Given a like-for-like replacement and a couple of years weathering then I reckon it would be practically impossible to determine when the windows were fitted.

Like Penners, I really doubt that such an issue would jeopardise a house sale, certainly not one where the prospective purchasers were serious about buying.

 

[JohnB]

Part of the £10k I knocked off the price I paid for my place was due to lack of a FENSA certificate

Good grief! Your vendors must have been desperate. :shock:

OK, just between the two of us, and with nobody else listening, if they'd told you that they weren't prepared to drop the price, would you have walked away?

Most of the £10k was due to the vendor telling porkies about other things. In fact I found out the biggest porky after I'd bought it, which is why you haven't been inundated with pictures and questions about the house . If I'd known what I know now I wouldn't have bought it. This is an ongoing "interesting" situation where no one else involved seems to feel any sense of urgency, and I'm extremely stressed. I'll relate the tale of apparent lies, deception and incompetence when it's finally sorted, but it's not a good idea at the moment :evil:

 

[AMc]

OK - an overall value of 1.6. You can't meet this with normal double-glazed units. Nor any filled with argon unless you go for very expensive specialist coatings as you need to have a glazing unit with a u-value of around 1.2. You could go krypton fill. I have no idea as to cost on this. Expensive I think. Specialist coatings? Also expensive. I got a quote for £540 + VAT for the specialist dgu's for a 6x6 sash window. That is before the cost of the wood or labour to make it or cost to install it.

When I was replacing my vinery glazing performance was very important and I did a lot of research. The room has an 8m x 4m sloping glass roof, 6m x 1.5m of windows + the gable end 4m x 2m and as part of a whole house assessment meets 2006 L1B with solid walls in half the property.

"Standard" hard coat low emissivity glass e.g. Pilkington K (1.6) doesn't meet that 1.2 U centre pain value but soft coat e.g. Saint Gobain Planitherm does and is widely available. I had some minor issues with getting the glazing company to use it as they preferred K glass because it has a long shelf life before being made into units while soft coat has to be ordered. We ended up with Planitherm argon filled units. This was more expensive than Pilkington K but not substantially more and in my case will comfortable pay for itself in the life time of the units. Argon filling is cheap enough that it was standard with all 3 glazing firms I got to quote. I wasn't able to find a local supplier to do krypton filling but it's impact is not as significant as soft/hard coating.

Data sheet on the last page of this PDF for Saint Gobain
http://www.saint-gobain.co.uk/Portals/Saint-Gobain/Media/Site%20Images/Innovation%20Centre/PDFs/SGG%20Planitherm%20TOTAL.pdf

My 3 quotes for all that glazing + 4 small windows + one large casement.

Original Supplier
Pilkington K £2300 PLUS VAT
SG Planitherm soft coat £3200 PLUS VAT

Alternative 1
Pilkingtons K £4000 PLUS VAT
Soft Coat £4500 PLUS VAT

Alternative 2
Low e £4300
Soft coat £4700

Original Supplier
Pilkington K £2300 PLUS VAT
SG Planitherm soft coat £3200 PLUS VAT

Alternative 1
Pilkingtons K £4000 PLUS VAT
Soft Coat £4500 PLUS VAT

Alternative 2
Low e £4300
Soft coat £4700

I'd be happy to PM you the names of the companies involved if you're serious about your window replacement as £540 is taking the micky.

 

[londonman]

Thanks for the offer and info. It's not the cost of the glass per se but the cost of making the units. There is a minimum price per unit. So a 6 x 6 sash, although using comparatively little in the way of glass, has 12 x the minimum price. I can understand why there is a minimum price because the amount of labour involved in making a small unit as opposed to a large unit is the same. It's only the incremental (low) cost of the glass and spacers that will be different. Hence my comment regarding duplex bars or stick-on glazing bars. If one went down that route then only two units would be needed - one per sash. The end result, however, would from an aesthetic point of view not be the same. Interestingly enough, adding glazing bars worsens the overall u-value.

 

[AMc]

Adding glazing bars introduces a thermal bridge - joining the two surfaces which are supposed to be separated by Argon gas. Warm edge spacers reduce this effect at a small cost but over the lifetime of the unit I would expect them to pay for themselves.

I have lots of replacement double glazed sashes which are made from individual units, some of which have failed - I'm making a supposition here but none of them have the necessary glazing bar widths to shelter the spacers from sunlight which is a known cause of failure. They're also pig ugly because the glazing bars are still much wider than the original 3 over 6 and 8 over 8s that were here before. We didn't fit them and if I had the cash I'd replace them.

The casements on the vinery the original windows were lapped pains of single glazing in tall thin frames. We reduced the number of subdivisions but used spacers and plant on bars to give the impression of the earlier design. I did mock up at the correct spacings but it looked like Strangeways. The plant on bars on the new windows are better looking than the fat glazing bars on the older sashes with many small units - the only reason the plant ons are as thick as they are is because the original wood work we "reproduced" was structurally supporting a lot of glass.

In your boat I would go for two larger sashes with spacers and plant ons that are appropriate for the window - that means you can have MUCH narrower glazing bars. If you could put the two types of DG window next to each other the only visual difference would be the fatter glazing bars from lots of smaller units.

Your alternative would be either a single glazed window with a double glazed secondary unit behind it, either a large casement or a pair of sashes.

BTW the vinery is more than 50 units on its own so I still think you're being quoted a high price.

 

[Joiner]

In brief here...

http://www.mightonproducts.com/catalog/part-news-breaking-news-c-92.html?osCsid=7f583f1b32b03daf5ce0ff298a3f1ce9

 

[AMc]

I clean forgot we replaced a 70's replacement casement with a fire escape compliant casement based on the remaining 3 over 6 sashes in the master bedroom. This has two large sealed units one divided into 3 and the other into 6.

I've posted pictures of the older replacement windows fitted before we bought the house, the newer replacement windows with bars and one of the original sashes with and without secondary glazing.

Older replacement window with multiple double glazed units

This window is made up of 12 individual units. It should probably be a 3 over 6 or perhaps 8 over 8 as the panes are the wrong shape to my eye anyway.

Detail of multiple unit sash

Note the 35mm glazing bars to allow rebates for both units. The unit only has a 6mm spacer.

Newer replacement window with single units, spacers and bars

A casement was used so that the lower section was large enough to meet fire regs..

Detail of single unit

Note the glazing bar is 24mm. Even though the double glazed unit is 4-16-4mm it's less obtrusive to my eye.

The original 3 over 6 in the same room before secondary glazing.

The original 3 over 6 in the same room with secondary glazing.

Detail of the frame of one of the original 3 over 6 sashes in the same room.

Note the 22mm glazing bar.

This now meets the specification for my 'whole house' SAP assessment for PartL1B 2006. This wouldn't meet the new regs and the internal glazing would need to be double glazed.

 

[londonman]

AMc - thanks for the info and also for the prompt re dgu pricing. Following your comments I went back to my new supplier to double-check...and I'm prepared to gvie the benefit of the doubt - but he'd quoted me for two sets of sash window units. So halve that price.

With regard to glazing bars, I hear what you say but at the end of the day, it comes down to personal and the customers preference. For my part, I don't like plastic in period properties. I get my glazing bars down to 24mm with the dgu units that I've been using up until now. Not as thin as the very elegant 15mm wide bars on a listed building that I am replacing...needed a special cutter for that moulding! But, equally nowhere near as fat as 35mm.

 

[AMc]

For my part, I don't like plastic in period properties.

I don't understand that comment either? What you see with either approach is the spacer at the edge of the unit or the spacer between the panes inside the unit, they look the same. If you can get your tollerences right with the position of the spacers and the bars you should be able to go all the way to 15mm?

The only thing I thought looked really odd was plant on bars without the spacers - then you get this grid effect when you're not square on to the window and you can see daylight between the front and back bars. I couldn't see why anyone would do that!

 

[Penny]

Slight deviation from glazing bars...A couple of years ago I obtained LBC to replace two high-level sash windows with french windows in my Grade II listed school. These were made to mimic the design of the sash and kept very narrow to fit in the existing openings. The chap who did the drawings tried to get permission for sealed, double-glazed units but was refused. Even though my builder said that he can get units which are very difficult to recognise as double-glazed. The french windows are not visible from any public place and led into my garden, which is fully screened. Our arguments about heat loss were unavailing. The french windows are in a large room which is 16' to the ridge and which had no insulation and very little heating. In desperation we fitted acrylic sheet across the inside of the windows, which does not look very nice but does the job. Regulations concerning thermal values and heat-loss are nonsense with regard to listed buildings as it seems to be something determined on the whim of the conservation officer who is in charge at the time.