Improving the Use of Energy in Buildings

Energy Advice > Saving Energy > Home Improvements

Energy Saving requirements for certain Home Improvements in UK Building Regulations

Building Regulations have for many years included a section ("Part L") on the conservation of fuel and power, that applies to all new homes built in Britain. From 1st April 2002 some of these requirements were extended to improvement work carried out on existing homes in England and Wales. (Different rules apply in Scotland and Northern Ireland.)

When do the new regulations apply?

The new Building Regulations apply in three main circumstances:

1. on new constructions such as new buildings or extension works;
2. where there are material alterations: works that affect, during construction or after completion, structural stability, fire safety or means of access for the disabled; or
3. with the provision of controlled services and fittings: the provision of a new boiler (or new hot water cylinder) to replace an existing one or the provision of one or more new windows to replace existing ones.

What has to be done with windows, doors and rooflights?

The regulations require that when windows, doors with at least half their area of glass, rooflights are replaced, the new units are properly draught-proofed and meet a minimum standard for the transmission of heat through the window, door or rooflight. This minimum standard is the same as would apply on a new home and effectively means that the new unit must be double-glazed with a wide air-gap (at least 12mm) and either filled with argon gas or carrying a low-emissivity coating. As windows meeting the new standards have been widely available in Britain for several years, they should not be significantly more expensive than basic double glazed units that no longer satisfy the regulations. Any member of the Glass and Glazing Federation's Fenestration Self-Assessment Scheme (FENSA) will be able to supply windows, doors and rooflights that meet the new rules. (The new rules do not apply if the work is just replacing panes of broken glass or parts of a rotting window frame or sash.)

What are the new rules about central heating systems?

The main rule is that boilers now have to meet a minimum specified level of efficiency, based on the Government's official test results (which are available on the internet at www.sedbuk.com). The minimum standard varies slightly with the fuel used:

Note that the SEDBUK rating is for guidance only. Full details of efficiencies for boilers and other heating systems including open fires and stoves, as well as the minimum levels of controls and pipe insulation, can be found in the Domestic Heating Compliance Guide. The guide also explains how to calculate minimum efficiencies when changing fuel as well as the boiler, and gives the procedure to determine those rare cases when it is permitted to install a non-condensing boiler, such as a combined gas fire and back boiler.

A modern boiler will not perform well if it has poor controls. To allow these high efficiencies to be achieved in practice, the new Building Regulations also require that any system has a time clock or programmer, a room thermostat (that will switch off the heating when it is not needed) and a hot water tank thermostat (except where combi boilers are used without a tank). They also require the system to be fully pumped (preventing older "gravity" systems) and the wiring in of a boiler interlock that will stop the boiler firing if neither the hot water nor central heating circuits requires any heat. A typical modern thermostat and programmer combined into a single unit.

There are separate provisions for solid fuel systems (coal or wood fuel).

The rules also require all newly installed hot water tanks to have adequate insulation (and a tank thermostat).

All newly replaced systems have to be tested by a competent person (who will usually be the installer) who is registered by one of three bodies (the Gas Safe Register [which replaced CORGI on 1 April 2009] for gas, Oftec for oil and HETAS for solid fuel). The installer also has leave proper operating instructions - it is no longer acceptable for them just to leave the boiler installation instructions behind!

What needs to be done with major alterations to a home?

As mentioned above, the new Building Regulations require the addition of insulation when there are material alterations being made to the property, most often as part of a structural change. In this circumstance, there is a basic requirement to add insulation to the level required for new buildings for roofs and floors affected by the changes.

In the case of structural changes to walls there is a requirement to add "a reasonable thickness" of insulation. This is not defined, as it will vary according to whether a wall has a cavity that can be filled, or if the wall is solid and will require some form of internal or external insulation. For changes to solid walls, one possible route may be to add a layer of the insulation material that can be fixed to a wall rather like a thick wallpaper.

When major elements of a roof structure are replaced, the rules are rather more straightforward, with the new roof structure having to satisfy the insulation levels (U-values) that apply to new homes. Similarly, where the structure of a ground floor is to be replaced or re-boarded, insulation should be added to the standard for new homes.

There are similar rules that apply on material changes of use, such as converting a barn to a new home or sub-dividing a house into flats.

Do the new Building Regulations apply to historic buildings?

The Regulations specifically exempt historic buildings (such as listed buildings, those in conservation areas and those of historical or architectural interest in National Parks or areas of outstanding natural beauty) if it is not practicable to carry out the changes in accordance with the new rules without damaging the character of the building. Owners of homes that may be regarded as historic are advised to speak first to their local council (or National Park) Conservation Officer for additional guidance.

...and are there Building Regulations for new buildings?

Yes. There have been rules on the conservation of fuel and power in UK Building Regulations since the 1970s. The detailed rules are highly technical and so we have not attempted to explain them here. However they have been set by Government to ensure that all new homes are easy to heat economically and do not unduly damage the environment.

A final warning! Although many of the new Building Regulations appear quite complex, the penalties for non-compliance can be quite severe. This web page is designed to provide a quick summary but should not be seen as replacing detailed advice from an architect or registered installer of controlled equipment. In particular the rules on windows, walls, floors and roofs have quite detailed requirements on U-values which are shown in the full Building Regulations. The approved documents can be downloaded from the Government's Planning Portal website. For further guidance, we recommend contacting your local council's building control officer or planning department.