When planning a ventilation system, there are a few building code requirements that you need to be aware of. In particular, the Building Code of Australia (BCA) states that you must have windows that are equal in size to at least 10% of the floor space, for the purpose of natural light - or 3%, for rooflights (or a proportional combination of windows and rooflights). When we talk about ventilaion it's worth remembering that skylights don't necessarily open to allow ventilation.
The 5% ventilation requirement
For the purpose of ventilation, an openable window or similar aperture is required to be at least 5% of the floor space in that particular area. The area itself may be defined just as one particular room, or a combined set of adjoining spaces. Also, in a room where there is no ceiling fan, the BCA states that you must achieve effective cross ventilation.
If you opt for a mechanical ventilation system instead, you need to ensure that the unit and its installation comply with Australian Standard (AS) 3666.1 'Air handling and water systems of building – Microbial control'. This will dictate the required flow rate and noise level. It also needs to comply with AS 1668.2 'Mechanical ventilation for acceptable indoor air quality'.
Sick building syndrome
Failure to comply with these standards could result in ‘sick building syndrome’. Studies have shown that people need fresh air and natural light for their health and wellbeing.
Most of the time, sick buildings are created by inefficiencies with air conditioning and ventilation. Much of the time, sick buildings are the result of a build-up of moisture and mould. Living in such a home can lead to eye, nose, throat or skin problems, or hypersensitivity.