Energy & Environment
Buildings with 15-20% rooflight area are more energy efficient
Incorporating rooflights into a building will cut energy use and reduce CO2 emissions. The benefits of natural daylight to the well-being of school children, care home residents, hospital patients and in the work place are well documented. The De Montfort University’s Institute of Energy & Sustainable Development is a respected authority on energy use and considerable research has shown that rooflights, combined with automatic lighting control, considerably reduces a building’s energy requirement thus lowering CO2 emissions. Simplified Building Energy Model (SBEM software) used to calculate the energy efficiency of buildings, shows that carbon emissions increase when the rooflight area is reduced below 20% of the overall roof. Combine this with the fact that studies show 93% of aluminium used in construction is recycled, rooflights should be a feature of any ‘green’ project.
BUILDING REGULATIONS PART L
A brief outline of the regulations is given here. However, we recommend you read our more thorough report here
New Build & Replacement Dwellings & Non-Dwellings
Latest changes in Part L states that rooflights should have a minimum insulation performance of 2.2W/m2.k. This is easily achievable with the Lonsdale ThermGard series glazing bars and low-e, double glazed units. Please see our QuikSpecs for typical examples of glass types. Note that rooflights with inferior performance can be used, but should be no worse than 3.3W/m2.K. However, steps must be taken to ‘trade off’ and improve other areas of the building in order to comply using the whole building method
Replacement Only Dwellings & Non-Dwellings
Rooflights being replaced may be assessed solely upon the centre pane Uvalue of the double glazed unit and need not take into account the frame Uvalue. This shall be no worse than 1.2W/m2.K.
Lonsdale ThermGard Patent Glazing System can achieve excellent insulation values when combined with high performance low-e glass. We are able to provide Uvalue Data Sheets specific to your project taking into account the bar lengths, spacings & glass type enabling you to more easily gain approval by Building Control. You can view an example here, please contact our Technical Department for advice
Part L requires that the building envelope’s air permeability should not be worse than 10m3 per hr/m2 at an applied pressure of 50pa The Lonsdale ThermGard system has been previously tested and found to compliant with latest regulations. Therefore it is suitable to form part of the buildings ‘air-barrier’ provided special attention is paid to the abutments with the building and additional air-tight components incorporated in accordance with our standard air-tight details. Please contact our Technical department to request our Air-Tight Binder.
Low-e glass used in double glazed unit combinations provide improved insulation. Typically, centre pane Uvalues are 1.6W/m2.K, but this can be improved by argon filling the cavity and using high performance, soft coat low-e glass to 1.2W/m2.K. The efficiency of the unit can be improved further be using thermally improved spacer bars. Please see our QuikSpecs for typical examples of heat saving glass or visit the glass manufacturers web pages shown on our links page.
Solar Heat Gain
The inside of the building can heat up during daylight hours due to the sun. This is termed as solar heat gain. To reduce this effect, solar control glass can be adopted to reflect heat and reduce glare from the sun’s rays. This lessens the burden on air-conditioning systems thus reducing CO2 emissions. In simple form, this may be body tinted glass in blue, green or bronze or more sophisticated, coated clear glass that allows maximum light transmission, but at the same time substantially reduces heat gain. Please see our QuikSpecs for typical examples of solar control glass or visit the glass manufacturers web pages shown on our links page.