Modern Building Services

MODERN BUILDING SERVICES JULY 2022 29 Ventilation is required in all occupied buildings. It is particularly important in areas where moisture is produced, such as kitchens or bathrooms, as excess moisture can lead to mould growth. Whether natural or mechanical ventilation is used, contaminants are reduced by bringing fresh air into the building. All systems need to be tested for correct flow rate and must be maintained regularly, including changing filters, to keep them working efficiently. Choosing the right filter Mechanical ventilation with heat recovery (MVHR) systems can reduce energy consumption while maintaining the required ventilation. They are an important tool in maintaining good IAQ and should always be equipped with the highest appropriate quality of filtration. The introduction of fresh air is clearly important but external conditions can have a major impact. For this reason, filters have a crucial role to play in removing major pollutants from the outside air as it enters a building via ventilation and air conditioning systems. As well as recognised standards for the application of filters, there are also ratings for low energy filters. The use of ePM1 class filters is recommended in buildings that are close to roads and in city centres, but the higher grade of filtration typically results in lower airflows and deviation of system design when used on retrofits, or increased airflow requirements and upscaling in fan size on new equipment. This consequence is because of the increased airflow resistance of higher-level filtration. Life cycle costings Whilst thought of as a minor factor in ventilation equipment, the investment in the type of filters that are used can have a large impact on equipment life cycle costs. We can calculate the expected energy requirement using the following formula that takes into account airflow, pressure drop, service time and fan efficiency. = Energy demand (kWh) = Average pressure drop over the filter during the service time (Pa) = service time (hours) = the flow rate by volume (m 3 /s) = Total fan efficiency (%) Example of an eight-pocket bag filter with a filter grade of ePM1 Air flow rate = 1 m 3 /s Average PD = 170 Pa Service time = 8,760 h Fan efficiency = 50 % A normal configuration of filters within an air handling unit would consist of coarse panel filters acting as a pre filter and then bag filters offering further air filtration. Using a panel filter as a pre filter would lead to increased overall pressure drop and, when relating back to the equation above, would result in a higher energy demand. Recent developments by filter manufacturers like Mann + Hummel have led to eco filters being manufactured with the sole aim of reducing the life cycle cost of equipment without compromising on IAQ. These filters include integrated pre filters and utilise nanofibres into the construction to provide low pressure drop characteristics usually found in glass bag filters with the added benefit of the depth loading that comes from synthetic material. When comparing complete life cycle costings that include purchase and disposal costs, we can realise an overall cost saving of up to 50% using eco filters instead of traditional filter media in addition to similar percentage gains in reduction of CO 2 emissions. Purification and filtration In addition to ventilation, IAQ can also be improved locally by the use of air purification and filtration. Solutions such as the indoor cassette range from LG (including Dual VANE 4-Way, Round and 1-Way units) feature a powerful 5-step air purification system which removes odours, germs, and PM 1.0 fine dust. With indoor air cleaning, 99% of ultra-fine dust (size 50nm~ 100nm), bacteria and viruses can be removed. The process comprises pre-filter, dust electrification, PM 1.0 filter, deodorisation filter and ioniser. The PM 1.0 sensor monitors air quality and with the central controller or monitor units, IAQ can be managed in real time with a remote control or smartphone. Wall-mounted units from the same manufacturer include an AirCare system with the following benefits: • Pre-filter - Traps large dust particles from the outset • UVnano - Removes 99.99% of bacteria on the fan (Including 0.1~0.3 in size) • Plasmaster Ionizer+ - Removes more than 99.9% of bacteria (Including 0.1~0.3 in size) • Auto Cleaning - Prevents bacteria and mould and dries the moisture inside the indoor unit to keep it clean. Efforts to combat the threat of indoor air pollution have been magnified by the need for improved air management during and after the Covid-19 pandemic. Effective ventilation and air treatment solutions have never been higher on the agenda and making the right choices on equipment to manage IAQ has never been more important. The Airpocket Eco ePM1 fromMann + Hummel A 5-step air purification system is used in LG indoor cassettes FEATURE INDOOR AIR QUALITY More information can befound at www.exi-tite.com