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emperature and air quality are the two main environmental factors that determine the comfort and health of building occupants.


Temperature control is particularly important as the impact of the climate emergency literally hits home, and temperature records continue to be smashed. You only have to look at the recent heatwave across Europe where some areas have been braced to suffer a blistering 480C, and which caused a series of dreadful wildfires on several Greek islands and in Algeria. And a remote township in China’s arid northwest has endured temperatures of more than 520C.


But the dangers posed by high temperatures is not


always so dramatic. Highly respected physicist and philosopher Dr Friederike Otto is senior lecturer in climate science at the Grantham Institute for Climate Change and the Environment, part of Imperial College London.


As she warned recently: “Heatwaves are killers.


They are called silent killers because people don’t drop dead in the street, but [they have a devastating impact on] the elderly, those with existing health conditions, people living in badly insulated housing, people, living in part of the city with lots of traffic so high air pollution… Heatwaves are a huge danger, life threatening.” Meanwhile, indoor air quality (IAQ) – defined as the


environmental characteristics inside buildings that can affect human health, comfort, and work performance – is also heavily impacted by high temperatures. Inadequate ventilation can increase indoor


pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. And high temperature and humidity levels can increase concentrations of some pollutants. The Air Quality Expert Group to the Department


for Environment, Food and Rural Affairs released a report late last year – Indoor Air Quality – that said: “The COVID-19 pandemic has served to heighten awareness of indoor air quality issues and the need


Creating the right atmosphere with multi-functional control


Combining temperature control with improved air quality, heat pump air handling units tick a lot of boxes; in particular, they boast high efficiencies and year-round comfort, as Tim Mitchell, sales director of Klima-Therm, explains.


for adequate ventilation in buildings, arguably acting as a catalyst for a paradigm shift in how this is approached.”


One of the most effective tools to control the indoor


environments of commercial premises is the heat pump air handling unit (AHU) for air conditioning (for temperature control) and displacement ventilation (for IAQ control). Displacement ventilation is a means of distributing


room air that employs a stream of slow-moving fresh air to displace waste air, which is forced out of the internal space via exhaust panels. Heat pump AHUs are ideal for displacement


Energy efficient environmental control


The 3DxHP Series three-coil integral DX heat pump air handling unit offers ultra-low carbon defrost-free operation with low installation costs and the option for bespoke design incorporating components such as humidifiers, attenuators, and carbon or HEPA filters. The built-in refrigeration system with variable speed scroll compressors can eliminate the need for


secondary cooling or heating systems such as chilled water and hot water derived from boilers. This reduces the energy required to move the secondary medium from the source to the AHU (pump power input), further maximising energy efficiency and therefore reducing the system’s carbon footprint. The built-in refrigeration system minimises the refrigerant content, eliminating pipe runs through the building and radically reducing the refrigerant content compared to variable refrigerant flow systems.


ventilation applications as they can provide a constant summer/winter supply air temperature due to the three-coil design and a variable speed drive scroll compressor. This unit can typically be adapted to most applications, particularly where space is a premium – only ductwork, electrics and an optional building management system connection are required. Heat pump AHUs are particularly well-suited to high-demand applications such as healthcare establishments and data centres. Since their refrigeration systems use one or more variable speed scroll compressors, close temperature control of the environment and high energy efficiency are possible since the system can react closely to varying performance demands. The zero defrost system that heat pump AHUs possess ensures uninterrupted supply air temperature in winter, with no need for a defrost cycle. In the case of my own company’s version of this technology – the 3DxHP Series (see box) – an innovative three-coil design allows air to be returned effectively during winter heat pump operation and incorporates heat recovery that is active all year round. A heat rejection coil located after the heat recovery


device provides some heat dissipation without affecting heat recovery, thus protecting the energy efficiency features of the product.


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Air handling units


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