Comment: The fight against mould

For many building facility managers and homeowners across Australia’s east coast, soaring summer humidity left a dangerous legacy – mould. Respiratory infections and irritation to the eyes and skin are just some of a long list of potentially serious side effects from exposure to mould.

Back in January, Sydney endured record-breaking humidity and other states too rang in the new year with sweltering conditions. Suffice to say, for a prolonged period, we experienced 24/7 humidity.

A high percentage of moisture in the air at a specific temperature is known as ‘relative’ humidity. Throughout our summer season, relative humidity did not dip sufficiently to inhibit mould growth – and mould loves moisture. When air conditioners are in operation, inside temperatures are cool. What’s problematic is the infiltration of warmer, moist outdoor air (especially during storm seasons). When this air lands indoors, it can result in condensation on cold surfaces, creating favourable conditions for mould growth.

‘Leaky’ buildings and homes are, of course, part of the problem. In warm climates, where lots of airflow is encouraged, leaks too may follow. Here, large windows, louvres and indoor/outdoor areas may not all be 100 per cent airtight when closed.

So, where to from here?

The goal is to remove moisture from interiors (ideally, at the point of creation). Natural ventilation and air conditioning can assist – but not simultaneously. In short, if the air conditioning is running, the place needs to be entirely sealed up.

Simple? Not quite.

When designing mechanical engineering services such as air conditioning, remember that communication and education are key. We need to understand precisely how a building or home operates. Don’t be aspirational about how your building or home is going to be used. Be realistic.

If some occupants routinely open certain parts of the building whilst the air conditioning is running, we (as service design engineers) need to know. Aged care facilities are a good case in point, where large numbers of residents may opt to have their windows and doors open while the adjacent common areas are air conditioned.

‘Mixed-mode’ services may be a suitable solution for sites like these. Here, both natural ventilation strategies and air conditioning can co-exist. But only if they’re well designed. Getting the balance right is a very nuanced task.

At entrances and exits, air locks (that trap air between two doors) may help maintain consistent internal air temperatures. Similarly, air curtains (where air gushes down above entranceways) can assist in countering exposure to warmer outdoor air when people enter or exit a building. In the case of specialist commercial buildings, high-tech moisture-removal systems can be very effective at prohibiting mould growth.

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For homeowners and homebuyers

I suggest homeowners look closely at rooms where moisture is most likely to be found, year-round. Think kitchens, bathrooms and laundries. Consider ways moisture can be removed from those rooms, otherwise it can be absorbed into surfaces, creating a prime breeding ground for mould.

Exhaust systems, that extract moisture and release it outside the building, are a good place to start. Ideally, exhaust fans should be connected to light switches that trigger their operation. The addition of in-built timers can also be beneficial to ensure exhaust systems run long enough to remove any lingering moisture.

New homebuyers should look for designs that favour natural cross-ventilation (where windows and/or doors are located opposite or adjacent to one another). Well-shaded windows (ideally with awnings) are another must-have.

Large windows are often a big part of architecturally designed homes – they look great and help connect occupants to nature. But without adequate sun protection, these windows may add to solar heat gain inside the home and, in turn, increase the property’s air conditioning load.

Ideally, look for project teams that prioritise both climate-responsive architecture and climate-responsive engineering solutions.

Ashburner Francis
ashburnerfrancis.com.au

Photography
Mindi Cooke

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