By Nicola Rivers, indoor climate specialist at Zehnder Group UK
Our recent summers have already been characterised by extremes in the UK’s climate. Temperature records soared beyond 40ºC for the first time, causing many to have to flee their homes in search of cooler and safer dwellings.
Overheating is a real problem in residential buildings. CIBSE defines residential overheating according to its fixed temperature test as, ‘when the internal temperature threshold of 26°C is surpassed for over 3% of the time’. Exceeding this temperature threshold for extended periods can affect occupant thermal comfort, health and wellbeing as well as productivity.
Within the UK Building Regulations, Approved Document Part O provides guidance to building designers on mitigating overheating in residential buildings and reducing these effects. Its prescriptive approach to optimising glazing, solar shading and natural ventilation clearly outlines preferred solutions to keeping a building cool.
But problems occur when external factors dictate that passive ventilation can’t be used to control internal temperatures and then Part O lists alternative means - from acoustic façade vents and mechanical ventilation to mechanical cooling.
Tackling Overheating
Combining ventilation with active cooling can offer a low carbon solution to overheating issues in residential properties and can be designed in conjunction with dynamic thermal modelling.
At Zehnder, we approach overheating with seven steps. Our cooling hierarchy consists of stages or options, some of which are complete standalone solutions and others which are combined, to deliver the required level of cooling capacity, including ventilation and humidity control.
These range from purge ventilation in the form of acoustically treated inline extractor fans, radial ducting to reduce noise, leakage and to maintain lower running speeds, and pre-insulated ductwork to ensure continuously insulated air distribution. Chilled water coils like the Zehnder ComfoPost also work in conjunction with the MVHR system. When linked to a centralised chilled system or reversible heat pump it can provide pre-heating in the winter and pre-cooling in the summer on the supply/intake air.
But our pioneer product to mitigate overheating and supply effective ventilation into a property is the Zehnder ComfoAir Q600 with ComfoClime that provides a tempered-air solution to meet Part O, providing a ‘fit for purpose' product across the construction landscape.
The ComfoClime system combines heating, cooling, and ventilation in one unit, providing a viable solution to Part O/TM59. It features an innovative reversible air to air heat pump module that can provide both air tempering and space heating and uses passive measures to cool the property first before activating the modulating compressor. This results in a more energy efficient solution to provide a comfortable climate during both warm and cold periods.
For more information visit: www.zehnder.co.uk/en/sectors-knowledge/topics/overheating
