There are five key Certified Passive House design principles;
1
Air Tightness
Elimination of drafts.
2
Super-insulated & thermal bridge-free envelope
Retain heat energy.
3
Heat recovery ventilation (MVHR) Recycles heat energy & provides fresh air.
4
Water tightness
Essential for building durability.
5
High-performance joinery
Building enclosure
3. Ventilation
Since passive houses are airtight (you can read more about airtightness here), mechanical ventilation is necessary to maintain indoor air quality. These ventilation practices also contribute to energy efficiency and occupant comfort, and we ensure a comprehensive approach that may include natural ventilation strategies that harness natural airflow and wind patterns for summer cooling.
The most common passive home ventilation systems are Mechanical Ventilation with Heat Recovery (MVHR) or Energy Recovery Ventilation (ERV) systems that bring in fresh outdoor air while recovering the heat (and, in the case of ERV, humidity) from the exhausted indoor air. This process reduces the need to heat or cool incoming air from scratch, contributing to energy efficiency.
The primary difference between HRV and ERV lies in their handling of moisture transfer. HRV focuses on heat recovery and is ideal for cold climates. At the same time, ERV goes a step further by transferring moisture, making it suitable for a broader range of climates, especially those with humid conditions.
It comes down to the location’s climate, energy efficiency goals and indoor air quality requirements.
Whilst introducing fresh air to the habitable spaces, 24 hours, seven days a week, we are also exhausting stale air from other spaces such as the bathrooms, kitchen, laundry, and other areas where moisture is generated. The exhaust air goes through a heat exchanger. Up to around 90% of the heat energy from the warm, outgoing air is transferred to the cool incoming air without mixing, to warm it up before it’s delivered around the house. That’s where most of the energy efficiency comes from – the money used to warm the air in the house is recycled by the heat exchanger.
We also look at cross-ventilation for cooling, which strategically places windows on opposite sides of the building so that air can flow through, creating a breeze and effectively replacing the indoor air when outside conditions permit, usually in summer. We can design with high and low windows for warm air to rise and escape, drawing in fresh air through the lower openings. Or we can design an interior courtyard to create a space where outdoor air can naturally flow into the building.
Clerestory windows can be placed high on the walls, just below the roofline, to allow warm air to escape while providing natural daylighting to the interior. However, creating an energy-efficient building is a fine line between heat gain and natural air ventilation from opening windows.
The effectiveness of these strategies depends on factors such as climate, building orientation and the style of the passive home.
Curious about how a passive home can change your life? Request a free consultation and learn how you can adopt eco-friendly living. Give us a call or fill in the form here.
