The two primary ventilation systems used in New Zealand are balanced pressure and positive pressure systems. Each system offers particular operational advantages depending on the region.

Positive pressure systems are often considered suitable for coastal areas such as Auckland and Tauranga, while balanced pressure systems may be more appropriate for colder inland regions like National Park and Queenstown.

Key differences include:

• Positive pressure systems are typically automated with variable speeds and can deliver higher airflow rates when needed, while many balanced pressure systems require manual adjustment of air speed. Positive pressure systems generally have a much higher airflow rate than balanced systems.
• Balanced pressure systems can recover up to 80% of the energy within the home; for example, if the indoor temperature is 18°C, the supply air may reach up to 14°C. Positive pressure systems draw air from the roof space, which can be warmer during the day, potentially providing higher supply temperatures depending on environmental conditions. Positive pressure systems may adjust or halt operation based on temperature sensors, whereas balanced systems may require occupants to manually manage fan speed and use an additional heat source.
• Positive pressure systems can employ high-grade filters (such as F7) that capture particles as small as 0.3 microns, including dust, pollen, and mould spores. In contrast, many balanced systems use G3 filters effective down to 10 microns, which may not remove all smaller particulates.

Common misconceptions about positive pressure systems include:

• The belief that roof space air is stale or stagnant; however, regulations require roof spaces to be ventilated, which allows fresh outside air to enter. Filtration further improves air quality before it enters living spaces.
• The concern that positive pressure systems introduce cold air in winter or hot air in summer; in practice, these systems often use temperature sensors to regulate fan speed or switch off automatically based on temperature differentials. Balanced systems may continue operating under similar conditions unless user intervention or an independent heat source is provided.
• Newer homes are too airtight for Positive Pressure, incorrect. All homes have good extraction venting points such as bathroom, ensuite, laundry and kitchen vents and around garage doors. All these areas are perfect as venting points for Positive Pressure and make it very effective.

This comparison aims to assist in understanding the operational differences between balanced and positive pressure ventilation systems in various New Zealand environments.

BDVair is a New Zealand owned and run specialist ventilation company with over 20 years experience.