Pressure tests and energy meters in Part L revamp

In the Government’s long-awaited strategy for improving Approved Document L: Conservation of fuel and power, losses from uncontrolled ventilation is seen as a major cause of carbon dioxide emissions.

Local authorities could insist that tests be carried out on new buildings larger than 1000 m2 to check compliance with airtight construction details.

The air leakage standard has been set at 10 m³/h/m² of building envelope (including floors) at a reference pressure of 50 Pa. This level is twice the current best practice value, but this may be progressively reduced to 5 m³/h/m² in 2002 and 3 m³/h/m² in 2007.

The tests will be at the discretion of Building Control and “approved inspectors”, based on design information, visual inspections and reports signed by a competent person.

“We don’t want to embark on wholesale pressure testing of new buildings,” said DETR’s head of Building Regulations, Ted King, “but we do want builders to get it right first time.”

DETR’s proposals vindicate the airtightness campaign launched in 1997 by CIBSE past-president Geoffrey Brundrett and Building Services Journal, with support from the BRE and BSRIA. “Clearly the proposal is a major step forward,” said Brundrett.

The airtightness rule is closely linked with a new approach to calculating U-values, which in turn will be connected to measures of ensuring continued heating system efficiency.

Other measures

DETR’s proposals contain a raft of energy efficiency measures, some of which will be introduced immediately and others which are proposed for future revisions of Part L (see ‘The major changes’).

The immediate changes include the introduction of a Carbon Performance Index (CPI), for air conditioned and mechanically ventilated buildings. Pass levels will be based on the current “typical” standard as listed in Energy Consumption Guide 19.

As expected, the DETR is proposing to extend Part L to cover maintenance and alteration works on existing buildings.

There will also be a “significant increase” in fabric insulation standards, but associated with an assessment method for judging the performance of the quoted heating system. The performance standard will be based on the amount of carbon emitted for one kWh of heating energy.

The introduction of a building logbook will provide a means of recording details of the installed building services plant and controls, their operation and maintenance, and forecasts of the building’s annual energy consumption.

For this reason the DETR has opted for the mandatory installation of energy meters and sub-meters to monitor key building services. This is intended to enable future revisions of the Regulations to cover central reporting and/or publication of such data.

“It also falls in line with other Government proposals for the routine reporting and inspection of combustion appliances,” explained the DETR’s Ted King.

Building overheating problems are also set to be addressed. Designers will be required to show calculations demonstrating that internal temperatures “will not be excessive”.

Lighting efficiency will be improved with a “challenging” standard of 40 luminaire-lumens per Watt (sic). Display lighting is covered for the first time at a reasonable level of average circuit efficacy ie not less than 15 lm/W.

“We don’t want to embark on the wholesale pressure testing of new buildings, but we do want builders to get it right first time”

Ted King

Domestic dwellings will be required to contain a number of light fittings that only accept energy efficient lamps. External lighting will also need to be automatically daylight-controlled.

DETR is also proposing to scrap the SAP energy rating method for dwellings and replace it with a Carbon Index, along with requirements for the proper setting up and adjustment of heating and hot water systems.

The consultation document includes a draft Regulatory Impact Assessment (RIA), which suggests that the additional construction cost of these proposals will range from £600 – £1400 per dwelling, and up to £10/m² of gross floor area for other building types.

Future plans

In response to industry’s wish for a “rolling programme” of changes to energy efficiency legislation, the Government is proposing to issue the Part L changes in four stages.

Stage one measures will be introduced no sooner than the end of 2002, while stage two measures are slated for late 2004. Stage three amendments would cover amendments to the Building Act, while stage four will cover further revisions to the standards.

Currently, stage two proposals include building performance (carbon) targets. Energy surveys based on CIBSE Technical Memorandum TM22 will be required for buildings deemed to fail the targets. Dwelling samples may also become subject to mandatory airtightness testing.

Stage three could include measures restricting the occupation of buildings until commissioning is complete and the operational information has been provided.

“If implemented, these proposals will yield significant improvements in the energy efficiency of new and existing buildings,” explained construction minister Nick Raynsford. “The proposals are technically sound, cost-effective and proportionate,” he added.

While the specific proposals in the draft Document will all be in stage one, the DETR says it is prepared to defer some measures for two years “to allow industry the time to adjust to the changes”.

Doubts, however, remain in the minds of those who think that the Government is hedging its bets with a staged process, and that measures industry finds unpalatable can too easily be put on the back-burner.

Andrew Warren, director of the Association for the Conservation of Energy, thought the proposals: “Too little, too late. We are twenty- five years behind our European neighbours,” he said.

“It has been an extremely long consultation period, and with a six month delay before the final document is issued, the first stage will not be completed before 2002. The government needs to pull its finger out,” he added.

CIBSE president David Wood agreed. “The proposals are great, but my main worry is that they are not being pushed forward far enough and fast enough,” he said.

Surprisingly, the proposals represent a five-fold increase in the carbon savings attributable to legislation, as laid down in the government’s draft climate change programme. Government had estimated that savings from the Regulations would be 0.25 MtC/y.

DETR now claims this was a “cautious estimate”, and that if the proposals were implemented “in full”, they would yield a cut of about 1.32 MtC in 2010.

The DETR is seeking responses to the consultation document by 29 September. The document and the editable consultation response form can be obtained from DETR on 0870 1226 236 or downloaded from www.construction.detr.gov.uk /br/br05g.htm