The Rise of the Clones




Window Systems – The rise of the clones

Take a walk down a local historic village anywhere in the UK and look at the vertical sliding sash windows - they are all different but all are local interpretations of an overall style. They may appear to be simple vertical sliding sashes to your family and friends but we know different, we are ‘window people’ and look at windows rather than simply through them, a truly sad state of affairs.

The truth is that all those historic vertical sliding sashes are different because there was no standardisation and each independent local craftsman made the windows in slightly different ways, using slightly different materials and slightly different proportions. The sash window may outwardly appear to a stable product but there was considerable development of the product with time and the late 17th century windows differ greatly from those of the late 18th century, to a window person that is.

Equally, early timber outward opening sash windows vary considerably with both the date of manufacture and who was making them. All this changed after the Second World War with a combination of a the construction boom and a shortage of materials - the English Joinery Manufacturers’ Association (EJMA) introduced a standard set of profiles for the manufacture of timber windows and the EJMA window was born. This ‘standard’ window set replaced the previous and variable tradition of a square edged casement that was flush with the front face of the sub-frame with the EJMA ‘stormproof’ covered joint. The basic design of timber windows has varied little from the EJMA standard over the past 50 years and for the outsider timber windows all look the same.

When PVC-U (or uPVC as it was then) was introduced into the UK in the late 1970s the boom years began. The Germans were huge, regimented, dogmatic and "hav vays of selling you tilt and turn vindows" but there was a myriad of window systems being developed specifically for the UK market by independent British companies. These companies were designing and making individual and innovative casement window systems and at this stage it was possible to identify the systems supplier by looking at the profile and seeing the quirks (good and bad) and features – they were all different, special and unique.

The 1980s were the golden years for the PVC-U business:

Everybody was ‘thirty something’ and had nothing to lose.

Innovation and change was the order of the day.

Glassex had the aura of a boomtown.

The smallest fabricator could carve a niche out for himself in a couple of years, set up as a systems company and finally make the big time as an extruder.

The "medallion men" ran riot and the fleet of foot made a fortune.

Businesses went up like weeds in a vacant lot and some perished when the boss had enough money to spend most of the year in Spain with his secretary doing market research.

In a sense the industry was a symptom of the Thatcher years and this was one of the rare times where all the stories of the good old days are true and truth is really stranger than fiction. People started out as teachers, became salesmen, set up as fabricators with the private box at the largest football club they could find and finally left for the sun in Florida. Chippies became millionaires and drove Maseratis. Fitters bought mansions from nailing frames into council terraces that had donkeys in the first floor bedroom. Great times but, like the dinosaurs, ultimately doomed.

By the 1990s the systems were largely fully developed; the race for critical market share had begun, new entrants were rare and the culling was about to begin. The 'thirtysomethings' were now 'fortysomethings' and used to the money. Risk taking was fine when you had nothing to lose, but was a different game when the kids were at public school, when one had to keep up a certain style and when good help was so hard to get. The problem at this stage was not how to get the money but how to hang on to what you had.

The signs were easy to see:

The corporate warriors entered the entrepreneurial window market. Marketing people, image consultants and corporate logo designers were suddenly all over the place. We started writing memos and stopped designing innovative window systems.

Products rapidly became commodities because in reality it was only ever a simple window.

The buyers became more sophisticated and service and price became the dominant factors.

The market became more stable and we knew what worked and what didn’t and in this climate it was inevitable that new product development would slow down and become less radical.

The rise of the clones was beginning.

In the 2000s these trends accelerated and PVC-U windows are now stable and mature, all the major window systems look the approximately the same (even without the benefit of an EJMA standard), all work tolerably well (if installed properly). To see that this is true, ask yourself these simple questions:

‘When was the last time you got excited about a new development in window profile design?’

‘What makes your current system technically better than the rest of the systems in the market?

PVC-U window system development has stalled; the product is now a commodity where the decreasing market price is undermining the whole profitability of the industry. If the clones are out there then maybe we should embrace them. There is even an argument for the equivalent to an EJMA standard for PVC-U windows. What would happen if the industry got together to design a copyright free ‘EJMA PVC-U’ window with common interchangeable parts (including gaskets, beads and reinforcement), a common look, common and extensive technical information and best of breed performance? This would remove the unnecessary and costly duplication of development costs, technical information, testing, fabrication tooling but would also reduce the costs significantly. It would also change the whole industry – systems suppliers would be seen as extruders again and the power of the fabricator would rise even more – but this is happening anyway. The model is already there in terms of the ‘freeware’ development of software such as Linux (free as in ‘free speech but not as in terms of ‘free beer’).

Think about it, what have we got to lose?

This may sound disappointing and disheartening but it isn’t really, it is simply a sign of maturity and an industry that will progressively become more moribund and stale unless something is done – the movers and shakers of the UK have already moved on to selling mobile phones.

The clones have won, get used to it, embrace it and move on.


How difficult is it to design an EJMA PVC-U window system?

Designing a window system from any material is not that difficult really. The constraints to the design such as production method, fabrication method and hardware are quite restrictive and the engineering constraints virtually determine the design. For PVC-U these are:

To meet the most common installation requirements the profile system depth will be between 60 and 70 mm.

To produce internally beaded products the profile system must be ‘reverse butt weldable’ and the profiles need to be broadly symmetrical about both the horizontal and vertical centre lines and to fit within a common profile ‘envelope’.

To use a range of hardware the profile system must incorporate a Eurogroove and hinge groove for location.

To use sealed units of up to 28 mm means that the system depth is defined.

To provide adequate cover, packing and drainage of the glazing area the rebate depth is effectively defined.

To avoid clashing on the outer frame when opening the sashes further defines the opening sash geometry.

To separate the drainage routes and the reinforcement, the internal chambers must be consistent across the outer frame and transom/mullion envelopes and link up for welding and chamber isolation. To avoid drainage routes breaking into the reinforcement chambers the location of the internal chambers are further constrained.

To match with the existing investment in accessory profiles the rear clip detail will match one of the precious few varieties of clip details.

Simply listing the engineering requirements effectively designs the product, with the exception of the glazing bead external visual detail (square, angled or scotia), which is repeated across the whole product range.

Of course there is more to it than that (but not a lot more) and profile designers will tell you about a whole raft of other constraints and problems. Much of this ‘mystique’ is a protection mechanism designed for obvious reasons – make it complicated to protect your job. We all do it!

Boring really and the ‘rise of the clones’ was predictable.

The newest constraint (or opportunity to differentiate the product) is the requirement for improving thermal performance. Previously this simply ‘fell out’ of the mechanical design but designers now are trying to optimise this. Unfortunately they are already running out of options; the mechanical constraints effectively prevent radical changes and the limits are already in sight.

The clones have won and an EJMA PVC-U system simply makes sense.



Last edited: 11/03/10

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