The new Part L is to come into force three years before we thought it was! Oh my God!! What are we going to do??? Well, why not pour yourself a drink, sit back in a large leather armchair and peruse the first part of Building's E-Z-Read® guide to what's in store …
Why is Part L being revised so soon?
The new, tougher Part L of the Building Regulations will be launched next year, rather than 2008, as we were led to believe. The Office of the Deputy Prime Minister is busy preparing the text for the new regulations. It has been moved forward to help the government achieve its aim of cutting carbon dioxide emissions 60% by 2050. A second factor is the need to implement a European Commission directive called "Energy Performance of Buildings" by January 2006.

What are those interfering Eurocrats telling us to put in our Building Regs?
The directive is intended to create more energy-efficient structures by making users periodically measure their buildings' energy consumption. The idea is to discourage people from buying or leasing poorly insulated buildings, and thereby persuading clients, developers and housebuilders to make sure their products do not waste energy. It could also make enforcing the regulations easier as consultants and contractors would be keen to protect their reputations by making sure the finished buildings performed as designed. The directive also sets standards for energy performance and requires boilers and air-conditioning to be regularly inspected

What is the timetable for Part L's introduction?
The 12 industry working groups will submit their recommendations to the Building Regulations Advisory Committee in March.

BRAC and consultant FaberMaunsell will then have three months to write the consultation paper that will be published in July. The formal consultation period will end in October, and the Approved Document is due to be published in 2005, in time to meet the January 2006 deadline for the implementation of the Energy Performance of Buildings directive. All the parties involved have a lot on their plate.

So what is going to happen to energy performance standards?
They are going to get tougher. The Energy Performance of Buildings directive requires a move away from an elemental approach to a whole-building energy performance calculation for dwellings and non-dwellings. Those who prefer to calculate energy use using individual building elements will still be able to do so, but the U-values they will be required to meet will be made much tougher. The working panels that are debating standards will have to come up with very convincing arguments to convince the ODPM that the proposed U-values are too harsh.

Will any U-values stay the same?
U-values for replacement windows are unlikely to change.

Will Part L extend to parts of a building's envelope that are currently beyond the scope of the regulations?
Sort of. Large display and entrance doors in commercial buildings are currently exempt but can result in substantial heat losses and solar overheating. There is some concern that this exemption is being exploited, so the definition of what constitutes a display or entrance door will be better defined to plug this loophole. The glazing working group wants shop windows on the ground floor to be exempt though as they often need to be replaced because of town-centre vandalism.

Is anything else going to be introduced that affects the building envelope?
Thermal bridging. The government wants to quantify its effect as part of the overall assessment of the whole building energy performance. Improved thermal bridging design details could be offset against poorer U-value standards in the main elements of construction.

So energy performance standards are getting tougher. No doubt they will have to do the same to airtightness standards?
Yes. The ODPM is proposing to make it a legal requirement to pressure-test most non-dwellings. At the moment, testing is not compulsory and so only 10-30% of buildings are being tested. Furthermore the ODPM is considering reducing the threshold where testing is suggested from the current 1000 m2 down to 200 m2 and to raise airtightness standards. (See "Tough as old boots", above, for figures for air permeability in different types of buildings). The requirement to pressure test will extend to dwellings unless the housebuilders can prove their standards are sufficiently robust to avoid pressure testing.

How can the ODPM justify ordering these increases in building performance?
The ODPM is obliged to carry out a regulatory impact assessment to ensure that the costs of new regulations are not disproportionate compared with their benefits. With this revision the government has decided that a tonne of carbon dioxide costs society £70 at 2000 prices (this goes up by £1 a year, plus inflation) and has factored this into the regulatory impact assessment. This can justify more energy-efficient buildings because the additional costs of such buildings are not just offset against fuel costs but the costs of carbon dioxide to society as a whole.

What housebuilders think

Unsurprisingly, some sectors of the industry are concerned about another radical revision of Part L so soon after the last one. Housebuilders are one sector that will be affected as they market a finished product for sale.

For Dave Baker, technical director of the House Builders Federation, the main concern is that the U-value of external walls could be reduced from 0.35 W/m2K to 0.25 W/m2K. “If we have to increase the wall cavity width from 100 mm to 125 mm or 150 mm to accommodate the extra insulation this would cause problems with other Building Regulations,” he says. “You would need stiffer wall ties that would have negative sound characteristics and there could be structural issues.”

Baker is aggrieved that all the expensive testing that has been carried out for the robust standard details scheme for Part E of the Building Regulations could be wasted, and that all the published guidance could now be destined for the shredder.

Increased wall thickness would also reduce housing densities. “Making walls thicker by 25 mm or 50 mm might not sound like much, but we have run appraisals showing a plot with 100 houses could be reduced to 98 or 97 under the new proposals.” He says this has implications for PPG3, but the key issue is the increased cost to the industry. “The customer won’t pay for the difference between 0.25 W/m2K and 0.35 W/m2K,” he says. Overall Baker thinks the housebuilding industry can probably cope with the other proposals more easily.