What is passive ventilation?
It is a natural way of exchanging air in a building—without fans or electrical power. It operates based on temperature and pressure differences: warm air rises and escapes through chimney flues, while cold air enters through air inlets or window leakages.
What are its greatest advantages?
- Zero Electricity: It works automatically without the need for fans.
- Silent and Maintenance-Free: No noise, no vibrations, and no servicing required.
- Low Investment Costs: Vertical chimney flues and air inlets are sufficient.
- Ideal for Single-Family Homes: Perfect for small buildings where simplicity and economy are priorities.
What are its disadvantages and limitations?
- Weather Dependency: It works well in winter but poorly during hot weather. When the temperature difference is small, a "backdraft" (reverse flow) may occur.
- Lack of Control: You cannot precisely regulate the volume of fresh air or its parameters.
- Heat Loss: Cold air enters while warm air escapes—this can account for 30–40% of a building's total energy loss.
- Structural Requirements: It only works with well-designed ducts and inlets; it cannot be the sole system in high-rise buildings (typically above 9 stories).
Why does passive ventilation work better in winter?
This is due to the large temperature difference between the interior and the environment. Warm air has lower density, so it "escapes" upward, drawing cool air in from the outside. The greater the contrast, the stronger the ventilation draft.
How to make passive ventilation work better?
By implementing hybrid ventilation, which is a combination of natural and mechanical systems.
- In favorable conditions, it operates naturally (gravity-based).
- When the draft weakens, a supporting fan automatically switches on.
- The Result: Lower energy consumption while maintaining constant air exchange.
What if full flow control is required?
In that case, mechanical supply and exhaust ventilation is the preferred choice, often equipped with heat recovery (recuperation). This allows you to:
- Regulate the exact volume of air.
- Filter and pre-heat the air.
- Recover heat from the exhaust air, meaning you can ventilate the building without significant energy losses.
