This guide is intended to assist designers, builders and homeowners to incorporate Best Practice standards of
energy efficiency into home extensions. It deals with:
• specifying energy efficient lighting.
Domestic emissions arise from the use of energy for space and water heating, cooking, and the use of lighting and electrical appliances.
For the homeowner, specifying an energy efficient extension is a cost effective approach, because the additional cost (over what would have to be spent to meet the minimum requirements of the building regulations) is quickly recovered in reduced fuel costs.
- designing and building
Opportunities for achieving a high standard of energy efficiency occur mostly at stage 3, when the detailed specifications for materials and products are prepared. However, there are also opportunities at stage 1, because the overall form of an extension influences its energy efficiency.
- extension shapes
Homes and home extensions take many forms. They contribute to the rich architectural variety we find in our villages and towns. However, when planning an extension it is important to bear in mind that some forms are inherently more energy efficient than others.
Another important factor is the amount and orientation of glazed openings (windows, roof windows and glazed doors). Windows fulfil several functions: they provide views out, let daylight in and assist with ventilation.
An unheated, southerly-oriented, highly-glazed conservatory will provide comfortable accommodation during spring and autumn, and on a few sunny days in winter.
The building regulations in the UK impose ‘minimum’ insulation standards for domestic extensions. However, the recommended Best Practice insulation standards (maximum U-values) set out in Table 1 provide for a better overall standard of insulation, thus reducing fuel use, fuel costs and carbon dioxide emissions.
New ground floors should be insulated to the Best Practice standards.
- exposed walls
Exposed walls should be insulated to the Best Practice standards.
Roofs should be insulated to the Best Practice standards.
- thermal bridging
The building regulations in the UK require that extensions must be constructed so that there are no ‘thermal bridges’, or gaps in the insulation layers within the various elements of the building fabric (i.e. walls, roofs and floors), at the joints between elements or around openings such as windows and doors.
There are many combinations of frame type and glazing type that will meet the Best Practice standard shown in Table 1 (i.e. maximum U-value 1.8W/m2K). Glazing types include double- and triple-glazing with different spacing, low emissivity coatings, and argon filling between the panes.
In the UK, domestic buildings have traditionally relied on air infiltration through the building fabric to provide background ventilation. This is supplemented by extract ventilation fans or by opening windows when additional ventilation is required.
For houses equipped with gas- or oil-fired central heating, one of the key issues associated with an extension is whether the existing boiler has adequate capacity to heat the enlarged house. In many cases, the additional heat loss associated with the extension makes it necessary to install a new boiler with appropriate additional capacity, at significant cost.
- room heaters
Where the house that is being extended does not already have central heating, it is a good idea to consider the installation of a central heating system, with a condensing boiler, as part of the extension project.
In most homes, lighting accounts for between 10 per cent and 15 per cent of the electricity bill, and contributes significantly to carbon dioxide emissions. The building regulations in England and Wales require that new accommodation (including extensions) includes some light fittings that will only accept energy efficient lamps.
The Energy Saving Trust (EST) manages a labelling scheme for products of proven energy efficiency.The scheme currently covers appliances (washing machines, fridges, etc.
- Q and A
Questions and answers on energy efficent home extensions.