Frequently Asked Questions about Ventilation in the Passivhaus

Frequently Asked Questions about Ventilation used in a Passivhaus Certified property

By Ruth MacEachern

Product Manager

Below is a series of frequently asked questions and informative answers on ventilation in a Passivhaus certified property.

1. What is Passivhaus?

The Passivhaus standard maximises energy efficiency and user comfort through its fabric first approach, relying on the materials used to construct the dwelling and aspects such as high levels of insulation, building orientation, and shading to provide sustainable living. A mechanical ventilation with heat recovery system (MVHR) is required due to high airtightness levels which expels stale air and pollutants and circulates fresh, filtered air around the dwelling, recovering heat energy from the extracted air. This provides major comfort and health benefits for the occupants. 

2. How does Passivhaus ventilation work?

Ventilation in a Passivhaus certified property uses a mechanical ventilation with heat recovery (MVHR) system which incorporates a heat exchanger. This transfers heat from the outgoing stale air to the incoming fresh air which retains some of the heat that would otherwise be wasted in a traditional system, but is a huge benefit for airtight dwellings.

3. Why is mechanical ventilation heat recovery (MVHR) more suitable for a Passivhaus than natural ventilation?

Controlled ventilation is crucial in the Passivhaus to maintain indoor air quality, remove pollutants, and control moisture levels. Since the Passivhaus is airtight to minimise energy loss, mechanical ventilation with heat recovery ensures a continuous supply of fresh air without compromising energy efficiency. In comparison with other mechanical ventilation systems, MVHR does not rely on the unpredictability of the elements such as wind and sunshine. 

Good to know

Find out more about the running costs of an MVHR system and its long-term benefits on the overall Passivhaus cost.

4. What are the benefits of a mechanical ventilation heat recovery (MVHR) system in a Passivhaus certified property?

The key benefits include:

• Improved indoor air quality
• Reduced risk of moisture-related issues such as mould and mildew
• Enhanced comfort with consistent fresh air supply
• Energy efficiency through heat recovery
• Reduced energy consumption for space heating

5. How does heat recovery work in Passivhaus ventilation?

Heat recovery in Passivhaus ventilation systems requires the exchange of thermal energy between the outgoing stale air and the incoming fresh air. A heat exchanger  transfers heat from the warmer outgoing air to the cooler incoming air during the winter, and vice versa in the summer. This reduces the need for conventional central heating and air conditioning systems.

6. What are the main design challenges of mechanical ventilation heat recovery (MVHR)?

The objective of a mechanical ventilation with heat recovery (MVHR) system is to optimise energy efficiency while delivering comfortable living and health benefits. One of the key design challenges of integrating MVHR in Passivhaus design is selecting the correct products and designing a system to suit the building. This involves professional knowledge and experience to avoid costly errors.

7. How much does it cost to install a mechanical ventilation system (MVHR) in a Passivhaus?

This depends on the size of the building and its layout. For example, the Passivhaus UK cost for a typical 4-bedroom MVHR system is approximately £3,000-4,000. The installation price is additional to this, which will depend on the complexity of the ductwork. 

To budget for Passivhaus costs discover EnviroVent’s MVHR products. 

Good to know

Learn how the installation of mechanical ventilation with heat recovery in the Passivhaus certified property has had a positive impact on the environment and occupant health and well-being in these success stories.

8. Can a mechanical ventilation heat recovery (MVHR) system reduce a building’s carbon footprint?

Yes. While ventilation systems consume energy to operate, the energy efficiency benefits from heat recovery typically outweigh the energy consumption. This leads to a reduction in the carbon footprint of the Passivhaus. 

9. Can Passivhaus ventilation systems be integrated with other HVAC (heating, ventilation and air conditioning systems?

Yes, Passivhaus ventilation systems can be integrated with other HVAC systems for climate control, for example in an older house. Coordination between the ventilation, heating, and cooling systems will ensure optimal indoor comfort and energy efficiency.

10. What is Approved Document F?

This approved document focuses on ventilation and the quality of indoor air. Approved Document F serves as a valuable resource for professionals involved in the design, construction, and maintenance of buildings in the UK for addressing sustainability and energy efficiency considerations whilst creating a healthy environment for occupants.

11. How can a building achieve Passivhaus certification?

The Passive House Institute establishes the Passivhaus certification guidelines and can only be awarded by an authorised Passivhaus certifier. Achieving Passivhaus certification requires collaboration between architects, engineers and builders to implement rigorous design and construction practices that prioritise energy efficiency, comfort, and environmental sustainability. 

Good to know

The Passive House Institute (Passivhaus Institut in German) originates from Germany. It was established in 1996, trialling an inhabited family house built to reduce energy consumption. The Institute continues to research the Passive House concept and has become an international authority on Passive House building for energy efficiency.  

12. What maintenance is required for Passivhaus ventilation systems?

Regular maintenance of Passivhaus ventilation systems includes cleaning or replacing filters, checking the efficiency of heat exchangers, and ensuring proper airflow. It is essential to follow manufacturer guidelines and schedule professional inspections to keep the system running at its peak performance.