Understanding the new Part L of the Building Regs
A radical shift in the approach to energy-performance standards — Mike Duggan.
With the formal consultation process for the new Part L of the Building Regulations closing this month, MIKE DUGGAN highlights its scope and the issues raised.The Office of the Deputy Prime Minister (ODPM) has published proposals for more-demanding energy-performance standards for both new and existing new buildings, which will come into effect at the end of 2005. These new standards will become the new Part L of the UK Building Regulations and are part of the Government’s response to the need to reduce greenhouse-gas emissions as covered in the Energy White Paper and The Action Plan published in April 2004. For the first time, Part L will be published in four separate documents. There are two for dwellings and two for non-dwellings. For each, there is one for new buildings and one dealing with refurbishment and alteration work in existing buildings. This article just concentrates on the one for ‘new buildings other than dwellings’.
Energy performance The main headline is that the energy performance of new buildings will need to be about 25% better than the current Part L, which itself only came into effect in April 2002. This overall improvement is made up of two elements. • An improvement in the standard of energy efficiency of 15 to 20%, depending on the level of services in the building. • A benchmark provision of renewable-energy systems. This benchmark is intended to reduce carbon emissions from the building by a further 10%. Including renewable-energy systems is not a formal requirement, but if they are not included the equivalent carbon savings have to be achieved through enhanced conventional energy-efficiency measures. One of the most significant changes in the new performance standard is target carbon-dioxide emissions for heating, cooling, ventilation and lighting. This would have to be estimated using an appropriate whole-building calculation method. This whole-building approach would mean that developers and builders have a great deal of flexibility in how they achieve the target. Some might prefer to concentrate on improving the envelope performance by including more insulation in the walls, floor and roof, and specifying better performance windows. Others might wish to concentrate on the building-services plant (e.g. more efficient boilers and chillers, improved lighting or more energy efficient mechanical ventilation), or on renewable-energy systems.
Other targets As well as meeting the carbon target, the building has to meet a number of other standards. • Minimum acceptable standards for the various elements of the envelope and the HVAC and lighting systems. This is to ensure that the carbon target is not achieved through a relatively inefficient basic building that is compensated by incorporating a large amount of renewable-energy systems. • Ventilation systems should be capable of achieving the same specific fan power at part load as that achieved at the design flow. As part of this, it is proposed that all fans with a rated power greater than 1100 W should be equipped with an efficient form of flow control such as a variable-speed drive or variable-pitch fan. • Control of overheating; if any zone of the building does not have a mechanical cooling system, it should be designed so that the space will not overheat. This is to minimise the likelihood of a subsequent air-conditioning retro-fit. As well as assessing the basic design, compliance with the proposed new Part L requires a number of checks to be made on the quality of the completed building. These include the following. • An air-tightness test; the proposal is that this will become a legal requirement for all non domestic buildings with a flow area greater than 500 m2. • In a similar way, it is proposed that ventilation ductwork for systems with a capacity of greater than 1 m3/s should be the subject of leakage testing.
Showing compliance At first sight, it may seem that having to use a whole-building energy-calculation tool would make demonstrating compliance with Part L much more complex than previously. In reality, this approach should make demonstrating and checking compliance easier than before, since most of the rules are built into the software and therefore are not open to individual interpretation. This would create a much more consistent compliance regime. The proposals represent a radical shift in the approach to energy-performance standards. They focus on the key policy objective (i.e. carbon-dioxide emissions), they allow a great deal of flexibility for builders in meeting the standard, and they would facilitate the task of enforcement. They also put increased emphasis on ensuring standards are met in the actual building and not just on the drawing board. At the outset of the revision work, the ODPM asked FETA to be the lead industry body for heating, ventilation, air conditioning and refrigeration. FETA and its members have worked closely with ODPM officials and their Part L contractors during the consultation process which formally closes on 22 October 2004. A final industry consultation meeting has been held, which was well attended — an indication of how important Part L is perceived to the HVAC&R industry. We now wait for the regulations to be re-drafted to reflect the extensive input from the sector.
Mike Duggan is the technical manager of the Federation of Environmental Trade Associations (FETA), 2 Waltham Court, Milley Lane, Hare Hatch, Reading RG10 9TH.
www.feta.co.uk
Related articles:
