Modern Building Services

MODERN BUILDING SERVICES JULY/AUGUST 2021 15 FEATURE INDOOR AIR QUALITY A full system approach to IAQ Integrated heating, cooling and ventilation systems are, without doubt, the best approach to tackling IAQ. Fresh air introduced into the home or business dilutes and helps remove trapped air and contaminants in the home or office. In addition, viruses do not generally survive the outdoors, so dilution helps mitigate transmission from airborne viruses inside the building. In a small duct system, heated or cooled air is passed through the air handling unit and can be easily configured to accept outside air before being distributed throughout the interior through small, heavily insulated ducts. To ensure constant circulation the system uses a process known as aspiration creating a gentle suction around the outlets that draws room air into the stream of heated or cooled air. This delivers draft free heating with a temperature differential no greater than 1°C throughout a given space. As well as improving air quality the delivery systemmeans that there is no need for space-consuming radiators as warm air is delivered into rooms via small spotlight style outlets installed into the ceiling. Filtration Even when providing outside air, most of the air in a HVAC system is recirculated from the indoors. A recent study by the National Air Quality Testing Services revealed that indoor air pollution in UK homes and buildings is 3.5 times worse than outdoor air pollution. Dilution does a great job of reducing some pollutants, notably gases, but doesn’t remove larger particles. This is where filtration comes in, particularly when the outside air is of low quality, for example in built up areas. One of the benefits of using a centralised system to provide heating, cooling and ventilation is that air quality can be significantly improved at any time of the year through the addition of filters and air cleaners. High Efficiency Particulate Air filters are the most common in the UK and are designed to remove at least 99.97% of particles from the air. The least efficient filters are designed to keep the HVAC system clean so that it heats and cools properly. These filters will capture the largest particles such as dust, hair, and dander. Better filters will capture smaller particles but will also create more air restriction which can reduce air flow and cause problems with the equipment. As a result, the type of blower in the system is an important factor in deciding what level of filtration to use. Most conventional HVAC blowers cannot tolerate much restriction and ductless mini- and multi-splits have no capability at all. Air disinfection Disinfection is the process of killing pathogens and destroying viruses. There is only one known technology that can accomplish this while the occupants are in the room and that is ultraviolet light. It must be the right kind of UV radiation, however, and there must be precautions so none of the occupants are harmed. This type of disinfection has been used successfully for more 100 years in healthcare settings. Only recently, through Covid-19, has it become popular to use in a home or office. A UV light can be standalone whereby small fans pull room air into the device, exposing it to the UV light. These work well for a single room, but it is an expensive option for a whole building. A better solution is to install the UV light in the duct system. Air drawn through the ultraviolet lights destroy disease causing pathogens and microbes. This is particularly recommended for high-risk areas such as care homes. Comfort control Although often overlooked as part of IAQ, maintaining a comfortable temperature for a home or building is essential. It is also one of the most important strands of Public Health England’s Beat the Heat: Coping with heat and COVID-19 campaign. [v] While in the UK, efficiency drives have increased the amount of insulation and widespread radiant and underfloor heating means that we can easily achieve desired temperatures in the Autumn and Winter a series of record summers have found UK HVAC systems lacking in the hotter months. Integration of heating and cooling means that temperature adjustments can be made through a central thermostat and the temperature in a building need only fluctuate between two to three degrees all year-round. When it comes to IAQ and Covid-19 there is an immediate response needed to tackle the issues associated with recirculated air, but we also need a whole system approach to improve indoor air quality wherever we live, work and breathe. Download a free Chartered Institute of Plumbing & Heating engineers and Unico Systems heating, ventilating and cooling CPD online via www.bit.ly/CPDVent “Integrated heating, cooling and ventilation systems are, without doubt, the best approach to tackling IAQ.”