Monday, September 23, 2013

Energy efficiency, the new National Building Regulations

Part Xa to the National Building Regulations Sans 10 400
These new regulations became a requirement from November 2011.  They have been a "must do " requirement since May 2012.


These deal with :

1.    How we use energy to heat water

2.    How heat is lost and gained through roofs

3.    How we use energy for lighting

4.    How heat is lost and gained through glazing, ie windows and glazed doors.


1.    How we use energy to heat water,

The new regulations require that a maximum of half of the energy used to heat water can be electrical, the balance must be by an alternative source – solar geysers, heat pumps, gas.

Hotwater cylinders and hot water pipes must be insulated with a geyser blanket to a certain minimum requirement. Hot water cylinders should be positioned to minimize the length of the hot water pipes.

2.    How heat is gained and lost through roofs

Roofs are required to be insulated to meet a minimum requirement. The simplest method is to provide a 135mm blanket of cellulose fibre type insulation ( isotherm / aerolite type) but a combination of cisalation, fibre blankets, thicker insulating ceilings can be specified.

3.    How we use energy for lighting.

The maximum electrical energy useage for lighting in the home is limited to 5W per m2 of interior floor area. This effectively means that lighting should be a combination of CFL, LED or fluorescent lights. The old 60w globes, or multiple 50w halogen downlighters are unlikely to comply. Generally a combination of up to 15w cfl globes  and 6w led downlighters will comply.

4.    How heat is lost and gained through glazed elements.

Glass is a lousy insulator, and is now required to meet strict criteria in two ways - conductance of heat through glass, and solar heat gain through glass.

Conductance is simple, how we use energy to keep our homes warm when it is cold outside and cool when it is hot outside. The calculation is a function of the area of glazing in m2’s and the interior floor area of the space in m2’s, calculated separately per storey.

Solar heat gain deals with the magnification effect of direct sunlight through glass, and this can vary depending on whether the glazed element is facing north south east or west. West for instance is the worst from this point of view.

The area of glass is therefore limited to ensure it complies with the new requirements.

Elements which can help are :

Type of glass – single glazing, double glazing, tinted glass, specially treated glass, shading overhangs in front of the glass. Type of window frame makes a difference. For instance wooden and Upvc window frames are better insulators than aluminiium or steel.


These new requirements are now the law, and we as architectural professionals cannot get a plan approved without showing on the plan how the new work complies. We are also required to inspect the work during construction and on completion to ensure that what was actually built does comply.


These reg’s are similar to buying a hybrid version of a standard car.  Unfortunately being good and green is expensive L


David Holliday is on the national panel of qualified persons to take responsibility for these new requirements

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