The government’s decision on whether to introduce mandatory pressure testing of homes is going to upset some people – but will it be those who oppose the measure, or those who back it?

Emission impossible
Emission impossible

The government is about to fall out with a large section of the building industry. It will shortly be making a decision on whether pressure testing of dwellings should be made mandatory. If it comes down in favour of testing, housebuilders will be unhappy. If it opts not to impose tests, it will be criticised by those who believe pressure testing is the only way to cut Britain’s carbon emissions.

Mandatory pressure tests are designed to ensure that housebuilders build airtight homes, so preventing heat loss and improving energy performance. They are supported by those with the job of ensuring that the government meets its commitments to the Kyoto agreement and its goal of reducing carbon emission 20% by 2010.

Tests are vehemently opposed by housebuilders, who believe the imposition of mandatory pressure testing will cause costs to rocket and the delivery of new homes to plummet.

Dave Mitchell, technical director at the Home Builders Federation, warns that testing might hurt Prescott’s housebuilding targets. “It could delay the purchase of homes and that could undermine the confidence in the new-build sector.”

In the consultation document for Part L of the Building Regulation, the ODPM lays out two possible ways for developers to prove that their dwellings meet air-tightness requirements.

The first is to conduct pressure testing on the floors, walls and roofs of each dwelling type in a development. The second option is for builders to show compliance by using robust construction details – in addition it states that on each development site where robust details are used a pressure test should be carried out on a unit of each dwelling type selected by the building control body.

David Strong, managing director of BRE Environment at construction research group BRE, says it is vitally important that mandatory pressure testing happens along these lines. “There is no substitute for the benefits that can be accrued from pressure testing,” he says. “It delivers demonstrably better energy performance, and it’s also a useful proxy for build quality.”

His theory is that if builders know their dwellings will be tested, the quality of build will be much better because the consequences of failure are so expensive that nobody will run the risk of building poor homes. Evidence from Canada and Europe suggests the lessons of airtight building can be learned fast and painlessly, he adds.

Strong also believes bigger gains in energy efficiency can be achieved by pressure testing than by improving the fabric of the building. “Going beyond the insulation levels being proposed for the 2005 Part L revision could provide diminishing returns, if it is at the expense of not achieving a reasonable standard of air-tightness.”

But HBF’s Mitchell says that the government could ensure dwellings meet air-tightness requirements without relying on mandatory pressure testing. He suggests using a system of robust details similar to the system used to prove compliance with acoustic building regulations. These were put forward by the HBF when the government was considering introducing mandatory sound testing to prove dwellings complied with Part E of the regulation. From 1 July 2004, if builders used construction details approved and tested by Robust Details Ltd, they could avoid mandatory sound testing.

Mitchell says that a “pattern book” of Part L robust details could be interlinked with Part E acoustic details. “There have always been conflicts between E and L. For once we could tie them together in one pattern book for the home’s superstructure,” he says.

Mitchell also questions whether there are enough testing companies to provide mandatory testing from 1 January 2006, when Part L is meant to come into force. This will not be a problem, according to Stuart Borland, managing director of testing company Building Sciences. “There’s huge capacity at the moment. We geared up for mandatory testing in Part L changes in 2002, which didn’t happen. We have a lot of equipment that’s rarely been used.”

Building Sciences has pressure-tested many buildings since 2002 after it was recommended for non-dwellings. He says contractors who have had testing have built good buildings as it has forced them to improve workmanship on site. “They’ve been exceptionally good and will easily pass new targets in the next Part L changes.” In the draft changes to Part L pressure testing will be a legal requirement for most non-dwellings.

One potential problem with mandatory testing is that relatively still weather conditions are required to carry out tests. A BISRIA guide to air-tightness says that, ideally, wind speed should be less than 3 m/s, and according to a CIBSE guide 4 m/s is exceeded 50% of the time in most of the main conurbations across the UK. Borland dismisses such concerns. “These measurements are taken 10 m above the ground. At building level the wind speed is totally different and much calmer.”

In just a few weeks the Building Regulations Advisory Committee at the ODPM meets to discuss the matter and a decision can be expected soon. The BRE’s Strong fears that after all the dicussions, the ODPM may not introduce mandatory testing. “It would be a real cop-out,” he says. “Many builders regard robust details as a ‘get out of jail free’ card.”

He says nearly half of new homes are failing current air standards, which he blames on a lack of mandatory testing. “In 2002, mandatory testing was taken out of Part L at the eleventh hour. Since then there has been a raft of non-compliant houses and an inferior product.”

Soon we will know whether the government has been convinced that robust details can work for Part L. While the government ponders, the chances of the UK hitting its carbon emission targets by 2010 grow slimmer.

Mitchell says the HBF is already pressing for a year’s delay if robust details are given the green light by government. It looks as though we will be trailing behind our European neighbours for some time yet, whatever way the wind blows.

Under pressure: the debate

The case against mandatory testing
Dave Baker, managing director of Robust Details

Robust Details Ltd would like to provide a registration service similar to the scheme already in place for Part E, which would give builders an alternative to mandatory pre-completion testing (PCT). Like Part E, this scheme would aim to:

  • Improve levels of compliance with Building Regulations (for Part L, reducing overall carbon emissions)

  • Provide a large database of construction types and test results (among other things, this could “inform” future proposed changes to Part L)

  • Support the actions of building control bodies

  • Close the gap between “theoretical” and actual performance on site

  • Provide an industry-led approach to Building Regulations problem solving.

For Part E, the principal beneficiaries of the scheme are new homeowners, whose properties are built to standards in excess of the Building Regulations’ minimum requirements. In the case of Part L, the effect would be to reduce carbon emissions across England and Wales, to the ultimate benefit of UK plc.

Builders opting for the robust details approach would benefit from increased certainty and reduced delay compared with the PCT route, as all testing would be independently commissioned and managed by RDL. Just like Part E, RDL will produce, amend and update a “pattern book” of robust solutions. And like Part E, the outcomes from RDL’s monitoring and auditing will be shared with industry in a way that will enable everyone to benefit.

The case for
David Strong, MD, BRE Environment

Mandatory pressure testing would introduce a simple, and much-needed, pass or fail test into Part L and would result in a step-change in compliance verification and enforcement.

A recent survey found that nearly half of houses tested failed to achieve the worst acceptable standard for air permeability required by the existing Part L of the Building Regulations, which is 10 m3/hr/m2 at 50 Pa.

The study by the Energy Saving Trust and Energy Efficiency Partnership for Homes by BRE and National Energy Services was conducted on a sample of 99 new homes built to the 2002 Part L requirements. The air permeability measured ranged from quite tight at 3.2 m3/hr/m2 to substantially leaky at 16.9 m3/hr/m2.

Much of the air leakage in the houses studied was a result of poor workmanship – gaps were detected in the envelope around penetrations such as service pipes and flues.

The house designs were all based on 2002 robust standard details and had been “signed off” (upon completion) as fully compliant with Part L by Building Control, which clearly they were not.

UK requirements for air-tightness are woefully poor, when compared with Canada, Scandinavia and Germany, which have significantly more demanding requirements for air permeability, typically less than 3 m3/hr/m2.

Achieving higher standards of air-tightness with controlled ventilation represents one of the last “big wins” for energy efficiency.