Mechanical Ventilation in Passivhaus vs Traditional Constructions

Comparison: Mechanical Ventilation in Passivhaus vs Traditional Constructions

By Ruth MacEachern

Product Manager

Mechanical ventilation in Passivhaus design differs from traditional ventilation systems including the mandatory use of mechanical ventilation with heat recovery (MVHR) systems, airtight construction, energy and cost efficiency and improved indoor air quality. 

Passivhaus homes are specifically designed to reduce energy consumption, maximise indoor comfort, and ensure a healthy indoor environment. Traditional systems work by exchanging indoor air with outdoor air to maintain acceptable indoor air quality and comfort levels. Unlike mechanical ventilation systems, which rely on fans and ductwork to control airflow, traditional ventilation systems often use natural ventilation methods (opening windows and background ventilators) or mechanical fans to achieve appropriate ventilation levels in a property..

What are the differences between MVHR in Passivhaus design and traditional ventilation systems?

Mechanical ventilation nowadays differs significantly from ventilation systems used in traditional buildings in several key aspects:

1. Continuous ventilation with heat recovery- Passivhaus design uses balanced continuous mechanical ventilation, which ensures a constant supply of fresh outdoor air and the removal of stale indoor air throughout the day and night. Traditional ventilation systems, on the other hand, may operate intermittently or rely on natural ventilation through windows and vents.

2. Heat recovery – one of the key features of mechanical ventilation in Passivhaus design is the use of heat recovery technology. MVHR units recover heat from the stale air before it is expelled from the building. The recovered heat is then incorporated into the fresh air entering the building to warm the living spaces. This heat recovery process helps reduce energy loss and minimises heating costs. 

3. Airtight construction - Passivhaus buildings are more airtight than a traditional dwelling, which helps to  minimise air leakage and heat loss. This ensures that the mechanical ventilation systems used within Passivhaus design have high levels of  energy efficiency. 

4. Design and sizing - Passivhaus ventilation systems are carefully designed and sized by experienced Passivhaus consultants  to meet the specific requirements of each building based on factors such as occupancy, building orientation, and climate. Passivhaus design considerations include airflow rates, ductwork layout, and equipment selection to ensure optimal performance. Traditional ventilation systems, especially older versions, may not always have the same level of precision.

5. Indoor air quality - Passivhaus ventilation systems enhance indoor air quality by providing a continuous supply of filtered outdoor air and effectively removing indoor pollutants. This helps create a healthy and comfortable indoor environment. While traditional ventilation systems also aim to maintain indoor air quality, they may not always achieve the same level of performance as Passivhaus ventilation systems.

Good to know

Some ventilation manufacturers offer Passivhaus approved components to meet the ventilation requirements under the Passivhaus standard. EnviroVent is one of these manufacturers. Details of the available components and their suitability can be found on the Passivhaus component database. 

Find out more about the success of the Passivhaus design journey.

How does MVHR (mechanical ventilation with heat recovery) impact energy efficiency?

Mechanical ventilation with heat recovery or MVHR in Passivhaus design is highly energy and cost-efficient. By combining continuous ventilation with heat recovery technology and airtight construction, Passivhaus ventilation systems minimise energy consumption for heating and cooling while maintaining indoor comfort and air quality. Traditional ventilation systems are less efficient and often rely on fossil fuels for heating and cooling, which are expensive and have a detrimental effect on the environment.

Mechanical ventilation – a sustainable solution

Mechanical ventilation in Passivhaus design offers several environmental benefits which can support the reduction of carbon emissions. Here are some of the key advantages of mechanical ventilation systems:

1. Energy efficiency - by recovering heat from expelled air and using it to preheat incoming fresh air, mechanical ventilation systems help reduce the need for additional heating. This lowers energy usage and associated greenhouse gas emissions.

2. Indoor air quality improvement - mechanical ventilation systems ensure consistent and controlled airflow throughout a building, which contributes to a healthier indoor environment for the occupants.

3. Moisture control - mechanical ventilation systems, particularly those that include a relative humidity sensor, help regulate indoor humidity by removing excess moisture from the air, reducing the risk of mould and mildew.

4. Pollutant removal - by filtering outdoor air before it enters the building, mechanical ventilation systems help reduce indoor exposure to harmful contaminants. 

5. Climate adaptability - mechanical ventilation systems can be designed to meet the specific ventilation requirements of different climates and building types. 

To find out more about mechanical ventilation, including the benefits, cost savings and incorporating it into Passivhaus design visit Frequently Asked Questions about Ventilation in Passivhaus.