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Air filters

Updated: Jul 19, 2021

Air filters significantly improve indoor air quality and are an essential part of forced-air heating, ventilation, and air-conditioning (HVAC) systems because they are crucial to the efficient operation of the equipment. Good indoor air quality can assist homeowners reduce their carbon footprint, enhance the health of the house and its occupants, and improve home's energy rating. Homeowners should understand about the various elements and proper air filter installation to maintain their HVAC system properly.

Air filters are installed on the HVAC air handler’s return side to clean the air to improve indoor air quality and to protect the motor from particulate matters. If you have a heat-recovery ventilator (HRV) installed, there should be an air filter inside it to clean the outside air that is taken into the home. Furthermore, the air filters should be in easily accessible locations so it can cleaned or replaced as necessary. Select filters with high minimum efficiency reporting values (MERV) of 12 or higher to trap pollutants like outdoor dusts, pollen, airborne bacteria, virus particles, mould spores and odours. Nevertheless, whatever the MERV rating is, a filthy or dirty air filter can significantly lessen air flow that increases the HVAC equipment’s run time, which eventually will cause wear on its motor and energy consumption. For best possible operation of the HVAC system, filters should be replaced regularly (typically every 3 months) or cleaned frequently as per manufacturer’s recommendations.

If the HVAC air handler is in an accessible location such as a utility room or basement, the filter should be in the air handler’s return plenum side. The air handler should be outfitted with a filter media box that has a openable access panel cover with gasket to provide an airtight seal when closed. The filter media frame must be compatible for the size and type of the filter and can be fabricated on site by the installer or could be provided by the HVAC manufacturer. The size of the filter (thickness, length and width) impact air flow velocity and filter capacity. HVAC design professionals should take into account the appropriate filter size to ensure that the equipment can cope with the associated pressure drop, especially with the installation of high MERV filters. To decrease pressure drop and increase the filter surface area, several options include use of deeply pleated filters or larger-dimension filters.

Proper maintenance of air filters is critical for the overall serviceability of the HVAC system. Doing the above recommendations will improve the home’s indoor air quality, increase the HVAC system’s energy efficiency, and lessen its consumption of non-renewable energy sources.

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