LIGHTING Integration of roof lights to minimise energy usage


Industrial and commercial buildings across Northern Europe typically use 20-30% of their total energy consumption on lighting, so there is enormous scope for energy saving measures.


One of the most effective is in plane roof lights, which can be easily incorporated into pre-finished steel roofing systems. When combined with efficient lighting systems, they can help to significantly reduce energy use.


Roof lights increase natural light, but also create areas of low insulation in the roof. Heat losses are virtually matched by solar gains through the roof lights, although in the summer this can lead to periods of solar overheating of the building.


Hours of operation


Installing 10% of the roof area with roof lights provides a good starting point for designing a day-lit interior. In some cases, up to 14% could be beneficial, but at high levels you need consider total heat gains in the building.


High-bay racking and similar bulky equipment can have a dramatic effect on light availability. An effective approach is to use a lower area of roof lights to provide natural background light with point lighting where needed. We can provide assistance with modelling and selecting the most appropriate area of rooflights for your project. Contact us for further information.


Summary of effects of increased level of rooflights


POSITIVE EFFECTS


Rooflight n


Lighting type/efficiency


Size /% area


n Transmittance n U values n Layout


Solar gain


Increased fabric loss


Naw


Required lighting level for operations (lux)


Figure 6. Effects of rooflights on building operations and environment


64 Solar overheating


Air conditioning passive cooling


Internal colour and reflection


Heat generation Control system


Provision of natural daylight Reduced CO2


from lighting Solar heat gains in winter


NEGATIVE EFFECTS


Increased fabric heat losses Excessive solar gains and overheating during summer


Cost of installation


Increased maintenance requirement


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