thermal cycling without compromising performance. Ventilated facades as an element of a passive cooling strategy Historically, facades were expected to keep weather out. Today’s cladding helps to regulate heat, moisture and ventilation whilst supporting improved energy performance.
Unlike traditional external finishes
fixed directly onto the building fabric, rainscreen facades introduce a ventilated cavity between the external cladding and the insulated wall construction. Research from the Fraunhofer Institute
for Building Physics has shown that ventilated facades reduce heat transfer into buildings by helping to remove solar heat before it reaches the inner wall. Similarly, researchers at the Building Research Establishment (BRE) have highlighted the role of ventilated facade systems in improving summertime thermal performance, particularly as overheating becomes more common in UK buildings. The result is a facade that helps reduce solar heat gain during summer while simultaneously improving moisture management and protecting the insulation layer throughout the year. Passive measures first The government has adopted a ‘passive measures first’ policy when it comes to
housing design. Outlined in Approved Document O, the rules clearly state that mechanical cooling can only be used where enough heat can’t be removed without it. The Chartered Institute of Building
Services Engineers (CIBSE) TM59 has become the UK’s standard methodology for overheating assessment. It encourages designers to model • • • • •
facade performance natural ventilation shading
thermal mass orientation
rather than relying on air conditioning. One of the most effective passive cooling
strategies remains external shading. Architects have long used projecting roofs, deep reveals and brise soleil to reduce solar gain. Increasingly, facade systems themselves are becoming part of that solution and ventilated facades are one element of a wider passive cooling strategy.
Brise soleil panels are seeing renewed
interest. By interrupting direct sunlight before it reaches the primary building envelope, well designed cladding can drastically reduce surface temperatures and lessen cooling demand without relying on mechanical systems such as air conditioning.
Similarly, varying board orientation,
introducing expressed fins, combining projecting facade elements and specifying lighter-coloured finishes can all help minimise absorbed solar energy. Rather than designing separately for summer and winter, architects can achieve year-round environmental performance through a single integrated facade design plan.
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