Recent improvements to the thermal performance of buildings has had significant benefits for energy efficiency, but indoor air quality is often neglected when it comes to the design of these air-tight buildings.
Air Change Australia manager Shane Carmichael says designers today are far more energy conscious which is why buildings are better sealed. However, while this approach is delivering energy savings, the downside is reduced air flow.
Carmichael says he receives requests from many frustrated new apartment owners who are experiencing these issues. These include stories of one- or two-year-old apartments with severe mould on walls, water under carpets and constant condensation on the inside of windows.
Carmichael says the reason these problems have become prevalent in the last few years is in the way apartments are now built.
“Prior to concerns about energy efficiency, buildings were constructed in a fashion that facilitated infiltration of air from the external environment,” he says. “This allowed for a turnover of air, minimising moisture build up within the occupied space.
“More importantly, it meant that bathroom exhaust systems had enough capacity to perform their duty and draw moisture laden air out of the bathroom. The obvious disadvantage of this is that energy is lost through this infiltration process.”
Although better sealed building produce a positive result, air turnover is extremely poor.
Carmichael says today’s apartments have effectively become a vacuum, and bathroom exhaust systems are not functioning.
Moisture from showers and laundries are not removed from the space and continuous build-up results in problems with condensation, mould and mildew, he says.
“Condensation is caused when moisture-laden air comes in contact with a cold surface. Unfortunately, this also corresponds with colder days, where occupants are unlikely to open doors or windows. Many of these problems occur in cooler locations such as Canberra and Melbourne.”
A typical example is a day in Canberra when it is 20°C, the heating system is on, doors and windows are closed, and at 30 per cent relative humidity condensation will occur on any surface lower than 1.9°C.
“As moisture builds up from showers and laundries, the risk of condensation is increased, with the same air at 50 per cent RH condensing on surfaces less than 9.3°C,” he says.
“The problem is exacerbated further with excessive moisture and humidity. It should be noted that these cold periods can last several days or weeks, with little to no air turnover during this time.”
In addition to unsightly condensation, Carmichael says mould and mildew can cause more serious health problems.
Toxic poisoning can even occur, according to the federal Department of Health's “Healthy Homes – A Guide To Indoor Air Quality in the Home for Buyers, Builders and Renovators” publication.
It states that toxic poisoning may occur if various mycotoxins such as mould and VOCs become absorbed through the skin, the lungs or the intestine.
This can affect the human nervous system, while some fungi can infect various parts of the human body, particularly the lungs and the skin. Those with weak immune systems are most at risk.
So how do we go about controlling these issues? Carmichael says firstly, it is important to minimise condensation through elevating surface temperatures by double glazing windows, eliminating cold tracking and controlling temperature in the space.
“Secondly, the apartment needs to have sufficient air turnover, removing moisture-laden bathroom air and replacing it with fresh outdoor air,” he says. “Opening a window is always a good solution for this, but not always practical particularly in extremely warm or cold climates.
“The alternative solution is for a mechanical form of ventilation that both introduces fresh air and removes the polluted stale air.”
To maintain energy efficiency a heat exchanger system can be used which will typically use the warmer indoor air to preheat outside air before it is introduced into the apartment.
The heat exchanger will preheat the outside air to 16°C before supplying it into
the apartment.
This has the benefit of minimising the additional load placed on the heating system from the introduction of outside air, especially during extremely cold conditions.
Air Change has released the ERV-IC 70 product which is specifically tailored for this role.
Some of the features of the ERV-IC 70 include:
Packaged with energy-efficient air to air counterflow plate heat exchangers
Built in a low-profile design to fit into tight ceiling spaces
Access for fans, filters and electrical through one single access panel
Focus on construction and insulation keeping noise levels to a minimum
High-efficiency fans with variable speed controllers.
“As residential dwellings in Australia become better sealed and energy efficient, the problem of condensation, mould and mildew will continue to become more prevalent,”
Carmichael says. “Maintaining air turnover and controlling surface temperatures are key elements to eliminating these issues.
“Heat recovery systems in particular are a cost-efficient solution and should always be considered during installation or design.”