Changes to the Building Regulations mean that most of the window systems on the market will be obsolete in less than a year, but contractors appear oblivious to the danger they're in. Time to wake up?
Chris Macey is a worried man. In February 2002, just eight months away, the amended version of Part L of the Building Regulations will come into force. The industry is facing a double whammy. First, the insulation value for windows is to be increased by one-third. Second, that value will be calculated in a more stringent way.

Macey should be delighted with that prospect. As managing director of Wolverhampton–based window and cladding consultancy Wintech, his firm can assess whether the windows being specified meet the new standards. He ought to be rushed off his feet as fabricators and systems suppliers check that their products comply. But he isn't. "The worry is that many fabricators still do not understand the potential impact of these changes," he says.

The problem that Macey fears contractors have failed to spot is that when the changes to Part L are introduced, the method used to measure heat loss through windows will be more thorough. This means that many window systems currently in use will no longer comply. So far, steel, aluminium and PVCu systems are known to be in trouble – Wintech has not yet looked at timber.

The spokesperson for a PVCu manufacturer agrees: "People are not aware that it is a major problem, but it is. It is a potentially huge, huge problem." More of a worry is that nobody appears to be taking responsibility for it: contractors are looking to designers to ensure that their scheme complies; designers are looking to fabricators to provide compliant windows; and fabricators are looking to system suppliers to provide frame components that meet the regulations.

The responsibility falls on designers

The major contractor

The industry is sleepwalking into a crisis.

What the new calculations mean
The current method of calculation is based on measuring heat loss through the glazed area, measuring it through the frame and adding the two together to get a U-value for the complete system. What happens in practice, says Macey, is that fabricators use better insulated glazed units than the regulations require, then ignore heat loss through the frame. But the frame, and how it fits with the glazed unit, is important. Under the new rules, they will be required to calculate the thermal properties of three factors: the frame, the interface between frame and glass, and the U-value of the glazed unit itself.

Wintech's evaluation of frame systems has found that most could not be made to meet the regulations simply by using a better quality glazing unit. "Fitting the highest performing glazing system into most aluminium frames currently available will not help the units achieve the required levels of performance, particularly when using the more basic type of frame," says Macey. "Most aluminium systems are unable to achieve the new performance levels."

The fabricator is expected to comply with what has been specified

The designer

However, Robert Dongray of window and facade manufacturer Schüco International disagrees: "Some aluminium systems can be improved by increasing the size of the thermal break," he insists – although he does admit that systems using a resin-based thermal break will probably not comply.

One industry source claims that many PVCu manufacturers are not prepared for the changes, and as a consequence are not letting their customers know about them. "They are saying it does not matter because they are trying to clear their stock," says the source. Ron Rouse, technical services director at contractor Mansell, agrees: "That's exactly the game they play," he says.

In other words, a great many of the frame systems on the market now will be completely obsolete in less than a year.

We rely on the frame manufacturer to produce a product to meet the requirements

The fabricator

An increase in disputes
The implications of this problem are wide-ranging. With effectively obsolete systems still flooding the market, the concern is that many of these units will be installed in ignorance on schemes granted building control approval after the February cut-off. "Major contracts will be procured in ignorance using products that are non-compliant by many major contractors," Macey warns. Mansell's Rouse is most concerned about local fabricators: "They'll wait until they are forced into it," he says.

With nobody taking responsibility for compliance, it seems likely that Macey and Rouse are right. "The responsibility falls on the designers to ensure that their designs are compliant," says Liam Duffy, managing director of Mansell's specialised works division. He does, however, admit that on design-and-build contracts, the responsibility would be his.

Architect Richard Brown of ATP Group Partnership says he would expect a window fabricator to comply with his specification. Fabricators, however, depend on framing manufacturers for their information. "We rely on a systems manufacturer to produce products that meet the requirements of the regulations," says Mark Robinson of fabricator and installer James Gibbons. However, he too admits that, ultimately, the responsibility for ensuring that the product supplied is compliant lies with the fabricator: "They [the systems suppliers] do not have the same contractual relationship," he says.

It’s a long haul but we’ll be there in the next one to two years

The section supplier

At the moment, Robinson is waiting for system suppliers to provide data on their framing systems. "The systems manufacturers are working hard behind the scenes," he says. But Macey has concerns over the ability of the market to provide the enhanced quality products in the timescale. He adds: "There will be an increase in the level of disputes as a consequence of these changes [to the regulations], once building control asks the relevant questions and it is realised non-compliant products have been supplied."

Steve Discoll, chair of the District Surveyors Technical Committee, is aware that the changes will cause problems for the industry. He suggests that the way forward would be to have an appointed list of approved window suppliers.

But it is not just contractors and fabricators that need to be aware of the extent of the regulatory changes: architects, developers and quantity surveyors could be affected – particularly on schemes that will not be approved by building control until after the amended regulations come into force. "Windows that comply with the new regulations will cost significantly more, which could affect the viability of some projects," says Tim Cooke, a consultant at Wintech.

We are concerned over the ability of the market to provide the enhanced products in the timescale required

The cladding consultant

Small fabricators could be pushed out
The fact that many of the cheaper frame suppliers will now have to use expensive glazing systems could turn the window market on its head. "Many of the more expensive framing systems that incorporate a thermally efficient frame will be priced competitively against units that are assembled using a cheap, less thermally efficient frame, but which have had to enhance their performance using a more expensive glazing system," says Cooke.

The new regulations could see the end of many of the smaller fabricators, because of a more systematic approach to window design. "To comply with the new regulations will require a more scientific approach to window design – including the use of computer-based thermal simulation," says Macey.

This method is currently used by Wintech to predict the performance of a frame design by some manufacturers before they make an investment in new equipment. Macey is of the opinion that this is something all systems manufacturers and fabricators need to be doing. However, he is concerned that many are still unaware of the pressing need for action, given the regulations' imminent introduction.

But it is not just windows and doors that will be affected by the new regulations; curtain-walling systems, too, will be affected. The methodology for assessing thermal performance of such systems has yet to be introduced so the performance of many products has yet to be assessed.

"The implication of these requirements on curtain walling have yet to be fully understood but the effect could be even more dramatic than those on the performance of windows and doors," warns Macey.

How windows will need to change

  • Double-glazed units will have to be better insulated. The width of the air gap between the panes will be increased to trap more air. Wider glazing units with a cavity width of 16 mm will be the norm.
  • For gas-filled glazing, the type of gas in the cavity between the panes has an impact on a window’s thermal performance. The cheapest way of filling the gap is with air; other gases such as argon are better insulators, but more expensive.
  • Coated glass will be fitted as standard. Low-emissivity glass is treated on one surface with a coating that helps trap heat in a room.
  • Frames will be thicker both to accommodate the increased air gap in the glazing units and to allow for insulation improvements in the frame. Aluminium units will be most affected, as the width of the plastic isolator between the inner and outer framing profiles will have to be increased. Older style aluminium frames with a resin thermal bridge will no longer be used.
  • The style of windows may change: single large glazing units will become more common to keep frame areas to a minimum. If a number of smaller units are used, frame areas are larger.
  • What is Part L?

    Approved Document L is the part of the Building Regulations and accompanying guidance that deals with energy use in buildings. Officially entitled Conservation of Fuel and Power, it aims to cut carbon dioxide emissions from buildings as part of the government’s larger commitment to achieve a national reduction of CO2 to 20% below 1990 levels. Significantly, under the new regulations, the changes will apply not only to windows and doors fitted to new buildings but also to replacement units fitted to existing buildings. The new regulations mean that windows and doors will now have to be have be better insulated: the current U-value of 3.3 W/m2°C will be replaced by the tougher value of 2.0 W/m2°C for PVCu and timber-framed windows, or 2.2 W/m2°C for aluminium and steel-framed units. The regulations are due to come into force in February 2002.