Modern Building Services

20 MODERN BUILDING SERVICES FEBRUARY 2023 FEATURE HEATING T he drive to combat global warming, reduce carbon emissions and achieve Net Zero by 2050 sees the benefits of VRF systems in high-performance modern buildings in greater demand as they offer a more sustainable built environment, which has become more and more pronounced. Compared with traditional HVAC systems, VRF systems are a renewable and more environmentally friendly energy solution that can greatly reduce carbon emissions from commercial buildings. They also have characteristics of low operational noise, compact size, advanced comfort control, design flexibility, as well as high energy efficiency. As one of the best low carbon heating options available in the current market, together with these superior advantages, the VRF market in the UK construction industry will inevitably continue to grow in decades to come. Depending on the energy source, a VRF unit can be classified as an air source or water source system. While the former takes energy from the outside air, the latter extracts energy from a large body of water. The large water source could be a pond, lake, river, stream, seawater, or even underground water such as in old mine workings. These systems can also utilise energy sources that would otherwise be wasted, such as industrial cooling towers, and computer/server rooms, and turn otherwise wasted energy into useful energy to heat buildings. The energy absorbed by the outdoor unit is transferred to the indoor space for heating or cooling in buildings. In comparison, air source VRF systems are far more commonly used in the UK construction industry, but water source VRF generally has higher efficiency than air source systems as heat transfers better in water. The water sourced outdoor unit is typically installed indoors and requires a large water source for operation. While the air sourced outdoor unit is installed outside. Furthermore, the water source VRF system does not need to defrost operation and generally has low operational noise as there are no fans in the ODU. Unlike the air sourced unit where the outdoor air temperature is influenced by external weather conditions and can vary significantly throughout the year, the temperature of the water source is not affected by external conditions as much. Hong Cheng , Technical Writer, EU Engineering Centre at LG Electronics, says that Variable Refrigerant Flow (VRF) is an energy-efficient HVAC system with sophisticated controls and sensors integrated together. It can effectively control the indoor temperature to create micro-climate zones to suit each individual according to each occupant’s specific needs, in different zones of a building. Typical use of Variable Refrigerant Flow (VRF) applications in commercial buildings