HVAC Ducting Systems and Indoor Air Quality

Keeping your heating, ventilation & cooling (HVAC) system clean will not only save you money, but keep your employees healthier and more productive.


Ducted HVAC (heating, ventilation and cooling) systems are the most popular way of maintaining thermal comfort within residential and commercial buildings.

When these systems are new, they perform well, regulating the indoor temperature and humidity and providing sufficient fresh air to keep the occupants refreshed and productive. Replacing stale room air with fresh air also serves to purge the indoor air of carbon dioxide, volatile organic compounds and other indoor air pollutants.


How does indoor air move through a HVAC system?


The supply air from an HVAC system is a mix of returned room air, and fresh air from outdoors: the ratio of these two supply air streams is controlled by dampers within the HVAC’s air handling unit (AHU).


To maintain the comfort of building occupants, the fresh air exchange rate should be controlled to deliver about 10 litres per person per second. This corresponds to roughly 0.5-4 fresh air changes per hour for most buildings, depending on the number of occupants and other variables. This means that the total volume of the occupied space is replaced every 15-120 minutes with fresh air.


The cost of running an HVAC system typically accounts for about 40% of the total energy bill for a commercial building.


Conditioning the fresh air from outdoors, heating in winter and cooling in summer, forms a large part of that cost. It is understandable that building owners and managers would seek to minimize this cost by delivering just the necessary amount of fresh air. However, when insufficient fresh air is included in the supply air mix, the indoor air quality suffers due to increased levels of carbon dioxide and other indoor air pollutants.


The air handling units are also responsible for filtering the supply air to remove environmental dust, pollen, mould spores, exhaust particles, dust mites, fibres and other materials before distribution to the occupied spaces.


How do we keep our HVAC system clean and cost efficient?


Despite filtration, material does accumulate within the air ducts over time. If a filter is not changed or cleaned it becomes increasingly clogged with dust causing pressure build-up across the filter.  This can result in the filter collapsing, releasing its burden to downstream components of the air handling unit and supply air ductwork.


The material burden within air ducts reduces the efficiency of the system making the system more costly to operate. More importantly the ductwork may become a reservoir for contaminants such as fine dust, allergens, moulds, bacteria, asbestos and other fibres which adversely effects the indoor air quality creating a health and safety risk for the building occupants.


HVAC systems must be regularly inspected, maintained and cleaned. Duct cleaning involves cleaning all of the various elements of an HVAC system: supply air ducts, return air ducts, heating coils, cooling coils, condensate pans, fans, diffusers and grilles.


Need more information about duct cleaning? Contact us or call 1800 878 262.