Ducting: Friend or Foe?

Getting the ducting part of any project takes both design time and site organisation. Ducts can get re-routed because of issues on-site and this can affect how the HVAC system performs.

Performance is usually the main focus once the project is finished, despite any site alterations during installation, and this is understandable. The primary function of the system is to cool/heat/ventilate as per regulations and requirements.

But…what about the longer term? What impact does the ducting have on the building that it is meant to serve?

Up to now, the ducting in a HVAC has been either neutral – i.e. it simply does the job of supplying the designed HVAC air as it is meant to do, or can actually end up causing harm to the area, and people, it serves.

How does this happen?

Lets’ assume that there are no issues with, cold/hot spots, stratification or draughts from the system. What else can cause harm?

With the increased awareness of the impact of Indoor Air Quality on building occupants, there is a growing recognition of the part played by the unseen part of the duct; the inside.

We are breathing in 3 to 4 litres of air per minute, that’s approximately 15kgs per day. The importance of keeping this air as healthy as possible seems obvious, yet this aspect of our industry seems to play only a minor role.

There are regulations already in place for keeping ducts clean. The BESA (Building Engineering Services Association) website can give you access to the book on the TR19 regulation. This can also lead you on to BSEN15780 (cleanliness of ventilation systems, excluding kitchen extracts) and the Workplace (Health, Safety & Welfare) Regulations 1992.

The Corporate Manslaughter and Corporate Homicide Act 2007 refers to fire (and fire spread) from dirty ducting.

For microbiological issues there is TM26.2000 (information available from CIBSE) to give the client and contractor guides on how to test for, and treat, the various biological pathogens. This states that there should be “reasonable provision” for safe and comfortable environments.

The regulations also refer to keeping the AHUs & fan coils (as well as other the other system components; silencers, dampers, turning vanes etc.) clean for the same reasons as keeping the duct clean.

On top of all this, as ducts get dirty the airflow performance and energy efficiency of the system can both reduce.

Obviously, kitchen extract ducts are focused on more due to more acute fire risks and insurance requirements, but what about the condition of all the other ducts?

Given the weight of legislation, and the fact that there are specialist cleaning companies available to perform the necessary tasks on behalf of the HVAC company or direct for the FM provider or the end client, why is duct cleanliness and its impact on the occupants via IAQ no receiving more prominence in our industry?

During installation, access only needs to be made available for access to system components, not necessarily the ducting itself. This is the remit of the cleaning contractor that will follow on later. But, what if the client (occupier) doesn’t realise the need exists for cleaning the ducts? What if they know, but decide to continually put it off due to cost or the unwanted disruption?

What if the duct is never going to be accessible (think of the many HRV/MVHR & ERV systems installed in residential ceilings throughout the UK & Ireland)?

What can be done to help prevent the situation arising in the first place? Those in the kitchen extract side of our industry will already be doing what they can to reduce grease build up. But what about standard HVAC ducting?

Keeping the filters clean is one obvious answer and there are improvements happening in this area with air flow sensors available to email an alarm when filters start to clog up and require maintenance.

Heavier filtration in itself can only be part of the answer do to the decrease in energy efficiency it can cause.

UV lamps help keep the air handling unit clean from microbes which reduce the potential for microbes in the duct.

Also, the colder the off coil temperature in the system (and the lower the relative humidity), the less chance that microbes will grow in the first place. This applies AHU/FCU as well as the ducts.

Higher velocity airflows can prevent dust and dirt build up in the duct simply by virtue of the faster-flowing air holding any sediment in suspension. Everyone understands that a fast flowing river will hold its sediment in the water while further downstream when the flow becomes much reduced, the sediment is deposited on the river bed. The air in the duct acts similarly.

So there are a combination of actions that can be performed to reduce the dirt in the ducts in the first place, reduce the need for cleaning and help provide a better result for the client in terms of efficiency, costs and (perhaps most importantly) the health of the occupants by not allowing IAQ to deteriorate.

We see that we can stop the duct from becoming a “Foe”. What if we could make it a “Friend”? What if instead of trying to prevent the duct causing a problem, we turn it into a delivery system for positive IAQ?

We can use the items mentioned above and combine them with purification that actively removes the gaseous pollutants, as well as bio-pathogens, coming from both inside and outside the building. From this point on we can be using the ducting to deliver healthier air throughout the occupied space and actively improve the lives of the occupants.

We can take it one step further. By inserting newly available probiotics into the airstream that will land on the surfaces we can purify not just the air our clients breathe but also the keyboards, desktops, phones etc. they use every single day.

It is reported that it is cleaner to eat on the toilet that at your work desk due to the germs in the workplace! (I personally will not be testing that!)

We can go from a defensive role of trying to prevent a problem caused by unclean ducts, to actively providing a better place to work or live, improve health rates at work, residences and in caregiving situations via those ducts to use our HVAC industry for the betterment of all.

A way of achieving the above is The Ingenious Air? Small Duct System. An intelligent climate control system that has an optional high specification air purification module. It removes VOCs and other harmful pollutants. It also removes disease-causing viruses and bacteria, allergens, dust and odours.

Additionally, the system can add up to 100% outside air ventilation with heat recovery ventilation. This can further improve air quality and save energy. At the same time, it provides a safe and comfortable indoor environment with clean, purified air.

Backed by years of experience, research and development, various case studies and installed in trusted brands such as Apple, Subway, Pandora and more, isn’t it time your ductwork is more of a friend than a foe?

ACR News, Joe Flanagan/Ingenious Air, (2018). Ducting: Friend or foe? Retrieved 13 April, 2018.