Dear Nathan

I read the letter from Giles Willson of BFRC / FENSA with great interest.
 
For the first time since the debate began, your letter, above all others, contained the first seeds of some inklings of common sense!
 
He said that: “Currently to achieve a 2.0 if you use low emissivity glass, 16mm air gap you are deemed to be compliant. The magic specification to achieve a 1.6 U-value keeps on being requested.”
 
And that: “The work which has been undertaken by BFRC with the detailed simulation of thousands of window combinations and the resulting whole window U-value and WER means we can look at which combinations achieve the 1.6 U-value. One solution is that if you have a timber or PVC-U frame (as long as it has five chambers) and you use an IGU comprising: soft coat low-e glass, 90% gas filled and warm edge spacer bar, you will achieve a 1.6 U-value.”
 
The great confusion and thus the problem for the window industry in general over the whole issue of the new Document L and WER regulations is that of the level of proof. If the situation, as is being shouted loudest by those whom it suits, is that the level of proof required is for every single window / door to have its own unique U-value proven by individual simulation using a very specific make up of glass; then this industry can confidently look forward to a massive problem through its supply chain from extruder through trade fabricator to installer.
 
If on the other hand, there can be a more sensible approach to the 1.6 or 1.8 U-value requirement (as you intimated), the confusion that currently reigns could be avoided. Indeed, as your letter suggests, such a common sense solution may already exist.
 
At Sliders UK we have fully investigated our ability to comply and help our customers comply with the forthcoming changes in the regulations:
 
For our vertical sliding windows this was easy; we have contracted the BBA to manage our BFRC registration and will be offering A, B and C rated windows. A process made more simple by having ISO 9001 accreditation already in place.
 
For our unglazed BBA accredited and SBD approved patio doors we have had fully accredited simulations done which show the minimum glass specification required to achieve a 1.8 U-value. This is proven to be 90% argon filled units with float / aluminium spacer / Pilkington K. The implication being that a) this is the lowest specification of glass likely to be used now anyway and b) any change for the better in any part of this glass make-up (ie warm edged spacer bar or improved glass coating) can only lower the U-value of the whole product even further (to as low as 1.4 by simulations we have done so far).
 
This, surely, is common sense but if building inspectors or certification bodies require proof to the nth degree we will of course be able to obtain simulations for whole product using specific glass configurations. It just beggars belief that the additional carbon footprint of doing all this unnecessary work may be required!
 
For our bi-fold doors the situation, believe it or not, remains limbo; as there is currently no methodology agreed for simulating U-values for bi-folds, they cannot be calculated. As we are now at the end of August this situation is hardly likely to be resolved in any realistic time frame for the industry to prepare for this increasingly popular product range to be adequately certified. Accordingly, by implication it may be illegal to fit bi-folds by 1st  October!
 
Giles, your letter offered some hope of common sense – I just hope for all our sakes it arrives soon!
 
Yours,
 
Ian Longbottom
Director
Sliders (UK)