PHAM NEWS | APRIL 2024 Ventilation & Heat Recovery


Why we need to lower the temperature


With more frequent heatwaves and concerns about global warming, over- heating is becoming a problem in many UK properties. Nicola Rivers from Zehnder Group UK looks at some of the solutions that can help beat the heat.


R


ecent UK summers have shown unprecedented shifts in our climate, with temperatures


repeatedly surpassing 40ºC and causing nationwide discomfort as a result of overheating. According to future climate projections from the Met Office, under a high emissions scenario, the temperature of hot summer days may still surge by up to 6.8°C in the coming decades, making overheating an issue that won’t go away. Unlike the US and many


European nations, where infrastructure mitigates such weather conditions, the UK is largely underprepared, with 4.6m homes in England reported to have experienced problems with overheating. This forces many to seek cooler and safer environments during the summer months. Inner-city dwellers often flee


the extreme heat, especially in Urban Heat Islands such as London and Manchester, while others rely on plug-in fans to alleviate stifling indoor conditions, despite high electricity bills amid a cost-of- living crisis. Most of us readily


acknowledge the disruptive impact of high temperatures in homes, but many don’t realise that these effects can manifest into significant health problems, such as disrupted sleep patterns, increased heat stress, heat- stroke, impaired sleep and, in severe instances for the more vulnerable, premature death. According to CIBSE, neglecting


to tackle this issue could result in an estimated 4,500 premature deaths annually by 2050 – yet many installers are unaware of the issues and how to tackle this very real, modern-day issue.


Below standard According to research commissioned by The Climate Change Committee, a high proportion of existing homes in the UK still fail to meet the new overheating standard for new homes or are estimated to fail the current standard used in the buildings regulations to limit overheating. The problem of overheating


throughout the industry is being linked to the unintended consequence of building and


Nicola Rivers Indoor climate specialist at Zehnder Group UK


retrofitting properties to be more airtight and prevent energy loss during the winter months – yet now faced with the problem, many are unsure of how to tackle it. Addressing the risk of


overheating requires newly built houses to be constructed with a consideration of high temperatures, and that some existing homes are retrofitted to keep internal temperatures down during hot weather.


Part O guidance Approved Document Part O addresses the pervasive issue of overheating in residential buildings – defined by CIBSE as ‘when the internal temperature threshold of 26°C is surpassed for over 3% of the time’. Part O provides guidance to mitigate overheating, prescribing strategies such as optimising glazing, solar shading, and natural ventilation. However, challenges arise


q Combining ventilation with active cooling can offer a low carbon solution to overheating issues in residential properties


when passive ventilation is impractical due to external factors such as noise, security, or pollution restrictions on


window usage. Part O suggests alternative solutions, including acoustic façade ventilators and mechanical cooling, with their effectiveness modelled in accordance with the guidelines (TM59) to demonstrate compliance.


Fresh approach Traditional methods like air conditioning units combat overheating but compromise indoor air quality by recirculating potentially harmful particulates and stale indoor air. Their energy-intensive operation exacerbates the escalating energy crisis, straining the national grid and contributing to global CO2 emissions. Air conditioning units also


demand high operational expenses and introduce an additional service requirement to the standard building operations, adding further challenges amidst the cost-of-living crisis. They also typically remain inactive during the winter months when temperatures naturally decrease. So it’s time for a new approach


to beating the heat, such as using ventilation as a strategy and solution. Combining ventilation with a tempered air system can offer a better solution to overheating issues in residential properties and can be designed in conjunction with dynamic thermal modelling. These systems can significantly


reduce cooling requirements, as demonstrated by a recent study implementing the Passive House standard in Tall Residential Buildings, which saw reductions


37


of up to 40% in cooling needs due to improved enclosure performance.


More than cooling Mechanical ventilation systems, such as Mechanical Ventilation with Heat Recovery (MVHR), often serve as the foundation for addressing overheating concerns as they are adaptable to ensure compliance with best practice guidance like CIBSE TM59. However, our approach


extends beyond mere ventilation and cooling – it involves optimising the overall indoor climate to create a comfortable and healthy living environment throughout the year. Adopting a comprehensive hierarchy of ventilation and cooling solutions, we can offer standalone options as well as integrated ones to ensure the ideal solution is specified for buildings at risk from overheating. These include various


solutions, such as purge ventilation which utilises acoustically treated inline extractor fans, radial ducting to minimise noise and leakage, and pre-insulated ductwork ensuring continuous insulation. Additionally, ground-to-air subsoil exchangers that work alongside the MVHR system, offer pre-heating in winter and pre-cooling in summer to fulfil the required cooling capacity, including ventilation and humidity control. However, our flagship solution,


the Zehnder ComfoAir Q600 with ComfoClime, addresses overheating using tempered-air technology, making it perfect for new builds contending with environmental obstacles such as noise pollution or lack of shade. This system integrates heating, cooling, and ventilation functionalities, adhering to Part O/TM59 standards across a range of settings, from residential high-rises to care homes. Its innovative features, notably a reversible heat pump module, guarantee energy-efficient performance throughout the year. These solutions can be


seamlessly integrated into various building projects, effectively streamlining overheating concerns, delivering a ‘fit for purpose’ product for diverse construction projects and ensuring cost-effective and efficient planning and implementation. So, as temperatures soar and


buildings become tighter and taller, in line with efficiency and sustainability goals, the need to address the risks of overheating is more important than ever before. Taking control and understanding the best way to mitigate these issues is the first step in an effective overheating strategy. ◼ phamnews.co.uk/424/57


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