That's what makes the DETR's Part L document such essential reading. The proposals to tighten the fuel conservation aspect of the Building Regulations will affect everyone associated with the construction industry, from those who design and construct buildings to those who occupy and operate them.
At one time the name said it all: Part L: Conservation of fuel and power. Today, with 46% of the nation's CO2 emissions being produced by buildings, Part L has a much broader remit. For a start, the government has the climate change imperative. This is the Kyoto agreement which commits the UK to cutting its greenhouse gas emissions by 12.5% over 1990 levels by 2012. Labour has promised to double this, committing itself to a 20% reduction by 2010.
The latest plans for Part L have been devised after a softly-softly period of consultation, a delicate iterative process which has taken 18 months longer than planned. The result is a set of quite dramatic proposals, staged over an eight year period. So what are the key proposals in Part L, and how will they affect the services industry?
Dwellings
Proposals for dwellings include significant improvements to the elemental and target U-value methods. These will be introduced in two stages over two years to keep the housebuilders happy. There are also requirements covering the installation and efficient control of heating systems, along with performance standards for lighting systems and controls. The definition of material alteration has also been widened to bring more work on existing buildings into the scope of the Regulations.
For dwellings, the DETR is proposing to use the SEDBUK database (Seasonal Efficiency of a Domestic Boiler in the UK – part of the Standard Assessment Procedure) to let builders trade efficient boilers against fabric U-values. If a SEDBUK-rated boiler is installed, the minimum wall U-value would initially be 0.35 W/m2K.
Under the two-stage process this will tighten to 0.30 W/m2K 18 months after the regulations come into force (see 'The Part L staging process'). If non-SEDBUK rated boilers are used, wall U-values would need to be 0.31 W/m2K, rising to 0.27 W/m2K after 18 months.
DETR is also proposing a relaxation in the form of 'poorest acceptable U-values'. The U-values of walls and floors could be as low as 0.7 W/m2K if this is compensated by the performance of other elements, like boilers. This applies to both domestic and non-domestic buildings.
The other major change is the effective replacement of the Standard Assessment Procedure by the Carbon Performance Index (CPI). This will enable builders to show compliance by achieving a certain minimum on a scale of annual carbon emissions.
Non-domestic buildings
Proposals for the non-domestic sector include: improved U-values; measures to limit the exposure of naturally ventilated buildings to solar overheating; measures to improve the as-built and in-use efficiency of air conditioning, mechanical ventilation and lighting systems; provisions to improve building airtightness; and the fitting of energy meters with a long-term view towards mandatory energy reporting.
As with dwellings, the government is proposing to set carbon emission standards using an adapted version of the CPI. Initially only offices will be covered by the CPI, largely because they are the only sector covered by a benchmark database in the form of Energy Consumption Guide 19 (ECON 19). Pass levels will be based on current "typical" performance (the database median).
The efficiency of air conditioned and mechanically ventilated systems will be covered by the CPI, with the pass mark being related to the typical performance standard of ECON 19. Specific fan power limits have been set at 2.0 W/litres/s for new buildings, and 3.0 W/litres/s for refurbished systems (or new systems in refurbished buildings).
Hospitals and schools will be expected to conform to guidance issued by the NHS and the DfEE. This is an important issue, as the DETR is looking for schools to be removed from Crown exemption and brought under the aegis of the Building Regulations.
U-values will be improved, with that for walls initially increasing from 0.45 W/m2K to 0.35 W/m2K in 2001, and to 0.30 W/m2K in 2003. DETR is also proposing a switch from the proportional area method of calculation to the combined method used elsewhere in Europe.
The Part L proposals have already raised eyebrows over the link between domestic U-values and heating system efficiency using the CPI. Non-domestic buildings are covered by a calculation within the similar Whole Building Carbon Performance Index.
A maximum carbon intensity has also been proposed for heating systems. At full capacity, gas heating systems are expected to generate 0.01 kgC/kWh, while at 30% load this figure is 0.058 kgC/kWh.
Designers will be able to claim a benefit from using a combined heat and power system. Although this will assume all the heat is being used, the regulations will tighten up on this in time.
Mandatory standards and testing for fabric airtightness is the big issue. For the first time non-domestic buildings will be expected to leak no more than 10 m3/h/m2 of envelope (including floors). Building control officers (or so-called "competent persons") will be empowered to demand tests if they suspect the sealing is not adequate.
As an interim measure "to avoid overwhelming the industry's ability to deliver", a building will be deemed to comply if a pressure retest shows a 75% improvement or gets to within 15% of the pass mark. The air leakage index will tighten to 5 m3/h/m2 in 2008.
On solar overheating, Part L provides simple calculations that designers will have to use to demonstrate that space temperatures will not rise beyond 280C on more than ten days in ten years when subject to an intenal gain of 15 W/m2.
Part L proposes to improve lighting efficiency in offices and industrial buildings by stipulating that the initial average efficacy taken over the whole building be not less than 40 luminaire-lumens/circuit Watt. For other buildings this is 50 luminaire-lumens/circuit Watt, and for display lighting not less than 15 luminaire-lumens/circuit Watt. Lighting must also be marketed with the relevant photometric data to enable light output ratios to be established.
Part L provides a list of permissible light sources, but as there is no restriction on the first 500 W of lighting, there is life yet for the gls tungsten lamp. (The August-September issue of BSJ's sister magazine Light & Lighting contains an in-depth analysis of the lighting efficiency standards).
Building logbooks and energy metering enter the Building Regulations for the first time. Initially sufficient meters and sub-meters should be installed to enable building users to compare energy consumption with performance benchmarks like ECON 19.
Part L stipulates that new buildings should be provided with details of the installed building services, the controls, and the method of operation, along with forecasts of building energy consumption. The resulting logbook is meant to ensure that buildings perform as the designers intended.
This is a precursor for the future requirements for building owners and occupiers to undertake routine recommissioning – a form of MOT test – to sustain good performance over the building's life.
The staging process
Perhaps the most significant change to Part L is the proposal to tighten the regulations over several stages. Stage 1 of improvements to the document effectively comprises those measures which can be introduced quickly and with the minimum of disruption to the construction industry.
In most cases, implementation of new standards will be six months after the Regulations are amended, but some measures have been deferred until two years after the amendment to give industry time to adapt (see table 1).
Stage 2 improvements are slated for 2003 (beyond the next general election) and include those measures where more time is needed to ensure that there "are no technical...or enforcement reasons that would make the proposals unacceptable".
Stage 3, slated for 2005, embraces those proposals that require changes to the Building Act, while Stage 4 in 2008 would tighten up those measures introduced in stages 1 and 2. (For more details on staging).
The virtue of the rolling improvements to Part L is that it gives the industry time to develop products and construction practices. The downside is that long-term plans of any sort in government are a hostage to fortune, namely the parliamentary timetable. The Part L revision process has already slipped by 18 months – and changes to primary legislation like the Building Act are also prey to political whim and the outcome of general elections.
Finally, the DETR is at pains to point out that the requirements of Part L are not intended to be prescriptive. Builders and developers will be at liberty to come forward with their own ways of demonstrating compliance with the functional requirements of Part L.
Source
Building Sustainable Design
Postscript
You have until 29 September to comment on the Part L proposals.
