TECHNOLOGY VENTILATION
As louvres are an integral part of the building envelope, aesthetics are an important part of the specifi cation process. However, it is very important that performance criteria are not compromised. For example, louvres can be hidden behind features or perforated panels but this can increase resistance to air fl ow
Louvre systems are an effective way of improving a building’s energy effi ciency but, to ensure best performance and protection from the weather, building designers and engineers must consider a wide range of factors, says Simon Hunter
LOUVRES IN THE AIR
I
t is estimated that around 45% of the UK’s CO2
emissions come from buildings. As
successive governments have committed to reducing greenhouse gas emissions by at
least 80% by 2050, the ways in which buildings are designed and built is changing. The Building Regulations – particularly
Part L, which sets carbon emission targets for new buildings – are expected to be the regulatory vehicle for meeting these goals, and are expected to introduce further carbon reduction targets later this year. To meet the tougher requirements designers are increasingly turning to ‘fabric fi rst’ solutions. This means consultants are using high levels of natural light and ventilation and insulation, combined with more energy-effi cient building systems, such as climate control and lighting. Louvre systems can have an important
part to play in improving buildings’ energy performance. Needed on most buildings, these systems allow airfl ow – both intake and exhaust – to heating, ventilation and air conditioning (HVAC) and other building systems, while protecting these openings against rain ingress. As well as allowing natural ventilation, an
effi cient louvre system can improve airfl ow to building systems, which means less power is needed to move the volumes of air required.
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In the case of HVAC systems, the improvement in energy effi ciency can mean a smaller and less powerful system is required for space heating and cooling. There are three main types of louvres: screening louvres, standard drainable louvres and storm-resistant (or performance) louvres. Screening louvres have the simplest designs, suitable for locations where water penetration will not cause signifi cant problems and economy is the primary consideration, such as screening rooftop plant or in car parks. Screening louvres typically have simple
blade shapes, which allow good airfl ow but give limited defence against rain. Standard drainable blades give good airfl ow and some rain defence, but do not perform so well with wind-driven rain. They are used when occasional ingress is not a major concern and where some drainage of water is required. Storm-resistant, or performance, louvres,
on the other hand, provide moderate to good airfl ow with excellent defence against wind- driven rain. These are typically used when high levels of ventilation and maximum protection from the rain is needed. Performance louvres have blades with complex profi les and use the ‘tangential separation effect’ to force air entering the louvre to change direction rapidly. The complex blade profi le creates low vortex
May 2013 CIBSE Journal 43
Louvre systems can have an important part to play in improving buildings’ energy performance
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