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Thermal regulations in the UK

Structure Basics | January 1, 2006 | By:


Legislation to promote energy saving measures in new buildings has been tightened a number of times over the past 20 years, since the recognition that buildings contribute almost half the annual carbon dioxide emissions in the UK. The most recent revisions proposed to the Building Regulations were intended to reduce that contribution significantly—as well as to comply with European legislation that comes into force on 1st January 2006—by implementing wide-ranging rules on air-tightness, fabric thermal performance and equipment energy efficiency. However, debate within the industry—and indeed amongst government ministers—has delayed the implementation of the revisions until spring 2006 at the earliest. The contents of the revisions to Part L of the Building Regulations are broadly known, although mechanisms for measurement and monitoring are not yet published. We aim to identify key aspects of the changing legislation that will affect building designers.

The European context

In order to comply with the European Commission “Energy Performance of Buildings” Directive (EPBD), due to come into force in January 2006, buildings must be accompanied by an energy performance certificate. This will allow prospective tenants and purchasers to make informed decisions about the expected long-term energy usage of their asset, and for “public buildings” such energy labels must be displayed publicly. This requirement is expected to impact the commercial property sector over the coming years as responsible organisations seek to ensure that they occupy well-rated premises.

How such labelling is undertaken, particularly for complex buildings, is not yet clear. There are a number of different assessment methods that can be used, and a team from the Building Research Establishment (BRE) has been working to develop new calculation methodologies. The aim would be for every building—including existing buildings—to have a published rating (in kWh/m2 per year) that represents real energy consumption in use: i.e. it will take into account how premises are managed as well as how they are designed.

Key issues for Part L of the Regulations

Fabric Thermal Performance is always a target for legislative change: as materials technology evolves, improved ‘U’-values can be achieved for a building envelope. The current revisions are no exception, with maximum ‘U’-values expected to be set as follows (W/m2K):
Walls 0.35
Roofs 0.25
Windows 2.2
Floors 0.25

Within the existing regulations, it is possible to trade-off between areas of poorer-performing fabric, and other energy-saving measures, such as high-efficiency boilers. The indications are that although this mechanism will still be possible to a certain extent, there are more stringent “minima” to be met. This is likely to lead to more considered integrated design, to ensure that maximum benefits can be derived from elements such as transiently occupied atria acting as buffer zones, and balancing transparency with highly-insulated elements.

Air-tightness is once again under scrutiny, with a maximum permitted air-tightness of 10m3/h/m2. Robust details are already in circulation for ensuring compliance with the air-tightness criteria, but it is expected that air-tightness testing will become compulsory for all but the smallest new buildings.

Equipment Efficiency becomes more significant within the new regulations, with efficiencies specified for boilers (including seasonal adjustment) lighting and ventilation fan power. It has been speculated that mechanical ventilation and air conditioning equipment will need to be rated in much the same way as domestic white goods, such that energy-efficient products can be readily recognized by the market. Again, how this might be implemented or monitored is not yet agreed.

Renewable Energy is increasingly recognised as a key component to reduce energy demanded from conventional fossil fuels, and a proposal in the consultation documents identifies a requirement for non-domestic buildings to contribute 10 percent of their energy from renewable sources. This is expected to be challenging, as the market for solar heating systems, photovoltaics and wind turbines is still in its infancy.

Measurement methodologies

For dwellings, the existing Standard Assessment Procedure (SAP) has been updated to SAP 2005, which includes a number of refinements, such as use of CO2 emission rate as opposed to a carbon index, and including lighting energy as well as the opportunity to score from renewable energy sources.

For buildings other than dwellings, it’s a little more complex. The intention is to use a new method, the Simplified Building Energy Method (SBEM) which compares the newly designed building to a notional building of the same geometry and usage to determine the energy performance. New software is currently undergoing validation testing before widespread publication. Of course, energy simulation tools can still be utilised to determine expected performance, but such tools will need to be validated against the new performance criteria.

Code for sustainable buildings

The other standard pending implementation in the UK is the “Code for Sustainable Buildings” intended to come into force in spring 2006. The code sets targets, not just for carbon emissions, but also for water and waste management, embodied energy and material use. As a Code, rather than a piece of legislation, this standard is not necessarily binding, but it is anticipated that all public bodies will adopt its minimum requirements through their procurement processes.

Possible impacts of new regulations

Clearly, the ambition is to generate building designs that are more energy-efficient and so impose less of a burden on limited planetary resources. It is hoped that more thoughtful building design, and the introduction of new technologies and new materials that perform well will help meet the requirements. In terms of fabric architecture, the use of shading devices, and intelligent use of fabric-roofed transient spaces as “buffer zones” are some opportunities that could be harnessed.

Two major impacts on the construction period:

  • Designers requiring more time (and fees!) to complete necessary calculations and submissions to Building Control.
  • Possible delays in completion approvals, as inspectors are required to assess and approve more complex submissions, covering a wider range of issues

To some extent, construction professionals will need to apply the new regulations for a period before the real impacts are clear—but in the meantime, expect a certain amount of confusion and delay as the industry gets to grips with all the changes.

Tanya Ross is a frequent contributor to design and architecture journals worldwide.

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