Housing Specification Blog

Tackling overheating – a comfortable home all year round

July 23, 2015 PaulGroves Housing DesignHousing IssuesInnovationsPlanning & Legislation

Michelle Sharp, Group Communications Manager at Zehnder Group UK, talks perceived and actual temperatures:

Imagine getting into your car on a hot summer’s day after it has been sat baking in the sun.  You open the door and feel the heat hit you and your immediate reaction is to ramp the air conditioning thermostat down to ‘low’ and the fans up to ‘high’.  For a few minutes it’s sheer bliss.

However, once the air temperature has reduced to ‘low’ (normally 16oC) our ideal comfort level has been surpassed and the rest of the journey is spent alternating between turning the air conditioning on and off – never quite reaching ‘a comfortable level’.

The same is true of our homes during warm spells of weather and with three major factors causing increases in overheating including Zero Carbon energy efficiency agendas, Climate Change and Increased Urbanisation, keeping residential dwellings ‘comfortable’ for occupants is a fine balancing act – in fact keeping them cooler is becoming more of an issue in cities when keeping them warm!  Have you heard of the Urban Heat Island effect?  In cities unique microclimates can be created due to excessive heat build-up from solar gain and mechanical services and community heating pipework within apartment blocks as well as many over cumulative factors.

Thermal comfort levels are particularly important at night.  Environmental Design, Guide A1 advises that bedrooms should be 23oC or lower to have no effect on quality of sleep.  Research carried out by CIBSE and Arup2 tells us that 3oC is enough to turn us from comfortably ‘warm’ at 25oC to uncomfortably ‘hot’ at 28oC.  It seems amazing that 3oC can have such an impact on our comfort levels.

The thing is, it isn’t just temperature that plays a major role in these comfort levels, but humidity as well.  In order to achieve comfort in homes, we also need to pay particular attention to the effect of humidity on perceived versus actual temperature – the additional 3oC may just be perceived heat due to humidity levels.

Reaching to specify air conditioning systems really won’t help achieve true year round comfort in residential dwellings and will have huge energy impacts – which are definitely not needed.

In airtight and well insulated dwellings, the consideration of over-heating must be tackled in the most efficient and cost effective way – so as not to undo any of important energy performance work already implemented.

By reducing the humidity levels in the home you can also reduce the perceived air temperature and add to the comfort of the occupants.  The added benefit being that it will be felt throughout the entire home with none of the draughts or increased energy usage associated with other cooling methods. Comfort cooling technology integrated with your ventilation strategy means that you can get it right first time and maintain comfort throughout the year.

To discover more about overheating in modern homes, a copy of Zehnder’s eBook ‘Comfort, Health & Indoor Air Quality’ is available to download, along with a whole range of other tools and educational resources dedicated to the subject, at Zehnder’s Passive House website www.zehnderpassivehouse.co.uk

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