Balanced Ventilation vs Positive Pressure — What’s the Difference?

Balanced ventilation supplies and extracts equal air volumes, keeping indoor pressure neutral.

What is positive pressure ventilation?

Positive pressure ventilation works by pushing more air into a building than is exhausted out. This creates higher pressure inside compared to outside, which helps prevent untreated outdoor air from infiltrating through gaps, cracks, and openings.

The system typically consists of a supply fan that brings in filtered fresh air, while stale air escapes naturally through openings or through bathroom and kitchen exhaust fans. This approach is popular because it is relatively simple and provides effective protection against outdoor pollutants.

Positive pressure: pros

Helps prevent polluted air entering through gaps. Simpler system design with fewer components. Lower initial installation cost. Effective for PM2.5 protection during pollution events.

Positive pressure: cons

Pushes conditioned air out of the building, wasting energy. Can force humid air into wall cavities, causing moisture problems. No energy recovery from exhaust air. Higher long-term operating costs.

What is balanced ventilation?

Balanced ventilation provides equal amounts of supply and exhaust air, maintaining neutral pressure inside the building. Both incoming fresh air and outgoing stale air pass through the ventilation system, allowing for energy recovery and precise control.

In balanced systems with heat/energy recovery (HRV/ERV), the incoming and outgoing air streams pass through a heat exchanger that transfers energy between them. This significantly reduces the energy required to condition fresh air.

Balanced ventilation: pros

Energy recovery helps reduce heating/cooling costs. Precise control over air distribution and quality. Avoids moisture problems from pressurizing wall cavities. Humidity transfer possible with ERV systems.

Balanced ventilation: cons

Higher initial equipment cost. More complex installation with supply and exhaust ducting. Benefits from a well-sealed building envelope.

Key differences

Conclusion

Balanced ventilation systems are more advanced and suitable for modern buildings in Thailand. While positive pressure systems offer simple pollution protection, balanced systems with energy recovery provide superior long-term value through better air quality, humidity control, and significantly lower operating costs.

For new construction or major renovations, we recommend balanced ERV systems as the standard approach. While the initial investment is higher, the energy savings over time help offset it, all while providing better comfort and air quality throughout the building’s lifetime.