Modern Building Services

MODERN BUILDING SERVICES FEBRUARY 2021 11 FEATURE INDOOR AIR QUALITY More information can be found at www.daikin.co.uk/ indoorairquality. Ventilation Fundamentally, ventilation works to remove stale indoor air and replace it with ‘fresh’ outdoor air. While opening a window may, on the surface, appear like a suitable solution, this can in fact do more harm than good, allowing pollution from external sources to easily enter the interior space. Instead, correctly designed, installed, commissioned and serviced ventilation systems – as part of a building’s wider HVAC system – can help to prevent the ingress of outdoor pollution, extract water vapour, airborne pollutants and odours from the air, control humidity and ensure a constant supply of fresh, clean air to occupants. Striking a balance In our newer buildings, this can require finding a careful balance between energy efficiency and air quality. Given the pressure to reduce running costs and energy consumption, combined with the targets set by BREEAM and LEED assessments, the emphasis can often fall on achieving high levels of energy efficiency within modern building design. While this focus on making a building well-insulated and air tight can help to lower energy bills, it does also make it more difficult to create a natural flow of air around a building – leading to low oxygen levels and increased potential for allergies and odours, as well as the risk of condensation build-up. Through careful design and consideration, however, it is possible to strike a balance, meeting the required energy efficiency levels while simultaneously achieving effective ventilation and a clean, healthy and comfortable indoor environment. For example, there are whole building ventilation systems available with various energy efficiency features, such as variable refrigeration temperature control and the ability to reuse waste heat from cooling and refrigeration. Building Regulations In the UK, ventilation design is controlled by the Building Regulations Approved Document Part F, which sets out the criteria for both homes and ‘non-domestic’, primarily offices. Of course, it stands to reason that different building sizes and functions will require differing levels of ventilation. For example, the required ventilation rates for homes are based on the number of bedrooms, from 13 l/s for a one- bedroom home to 29 l/s for a five- bedroom property. In comparison, the total air supply and extraction for office ventilation is 10 l/s per person, with intermittent extract ventilation also required for specific areas, such as WCs, photocopying room and kitchens. Maintenance As well as designing and installing the ventilation correctly, regular servicing and maintenance throughout its lifespan is perhaps just as essential to ensure it continues to deliver a high level of performance. Given the system’s role of extracting airborne pollutants and providing a constant supply of clean air, the regular cleaning of a building’s ventilation is understandably crucial. Without the correct attention, dust and dirt can build up and affect the system’s ability to maintain indoor air quality. While ventilation units are already fitted with filters - primarily to keep the system free of dust, as well as to help remove particulate matter from supply air - there is still more that can be done. Regularly checking the supply intake and exhausts for signs of dirt build-up, pollution or contamination, or damage fromweather and animals, is good practice, as is inspecting the ductwork and indoor units. Any dust should be removed from the ductwork, with particular attention to the filters, heating and cooling coils and any change of direction in the ducting. For further guidance on ventilation maintenance, BS EN 15780: 2011: Ventilation for Buildings. Ductwork. Cleanliness of Ventilation Systems specifies acceptable cleanliness levels for supply, recirculation and extract air, grouped into three classes – Low, Medium and High – depending on the use of internal space. According to theWorld Health Organisation (WHO), air pollution from both indoor and outdoor sources represents the single largest environmental risk to health globally. Given this, it is clear that incorporating indoor air quality within modern building design is key, with effective ventilation at the core of achieving this clean, healthy and comfortable indoor environment for occupants to enjoy.