Modern Building Services

MODERN BUILDING SERVICES MARCH 2023 11 C IBSE defines overheating, according to its fixed temperature test, as when the internal temperature threshold of 26°C is unsurpassed for over 3% of the year. Exceeding this temperature threshold for extended periods can affect occupant thermal comfort, health and wellbeing, and productivity. It has been proven that surpassing temperatures of 35°C increases the chances of heat stress, which can have severe side effects such as dizziness, nausea, confusion and loss of consciousness and in some cases, it can lead to death. Climate change has led to increasing summer temperatures. Met Office future climate projections, under a high emissions scenario, suggest the temperature of hot summer days could increase by between 3.8 and 6.8 oC, in future decades and that we could see as much as a twenty-fold increase in the chance of hot weather warnings being issued 1 adding alarming concern to the issues overheating results in. In addition, experts claim that the global temperature is likely to rise 1.5 degrees above pre-industrial levels by 2051 and heatwaves will increase in frequency, making this an issue that won’t go away and should not be ignored. Challenges with overheating in modern buildings Building design often contributes to overheating in modern buildings. CIBSE has advised that if the issue is not addressed, 4,500 premature deaths per year are expected by 2050. Much of the problem lies, not just in what we are building but where we are building new apartment high-rises, where overheating is most prevalent. It is literally a case of location, location, location. Within the UK Building Regulations, Approved Document O provides guidance to building designers onmitigating 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 an apartment cool. If you pass all these prescriptive requirements, then job done. But problems occur when external factors dictate that passive ventilation can’t be used to control internal temperatures and the cooling hierarchy comes into play. If planning dictates that windows cannot be opened, Part O lists alternativemeans of reducing the order of preference from acoustic façade vents and mechanical ventilation tomechanical cooling. The predicted effectiveness of these solutions must bemodelled in accordance with TM59 to demonstrate compliancewith Part O. More and more inner-city conurbations are building upwards, like Urban Heat Islands such as London and Manchester. Developers are having to build higher and more compactly due to limited central city space. With locations like this, the external environment around the building can have a massive effect on the building’s usage and may affect the way occupants can ventilate their space. In central city locations, it is likely that other social impacts and infrastructure will need to be considered when finalising the design plans. For example, the building may sit next to railway, tube or tram lines or windows may open onto busy roads. Cities are often victims to higher levels of noise and pollution and, with a surfeit of retail space already available, more and more high- rise developments are being built with apartments on the ground floor, where opening windows to ventilate presents an unacceptable security risk. This can often result in 10-25% of apartments being unable to open windows due to safety concerns, security risks, excess noise and environmental pollution levels. Solar energy absorbed through the day by the building and then given-off later also provides problems in this instance. As the space cannot be ventilated via open windows, overheating can be shown to occur at night. ➜ Overheating continues to be amajor building problem, according to AndrewNash , Residential Divisional Manager at Nuaire. Tackling overheating when passive ventilation methods aren’t an option FEATURE AIR CONDITIONING, COOLING & VENTILATION