A Passive House, also known as Passivhaus, is a highly energy-efficient building that is conditioned passively with minimal (or zero) energy from fossil fuels. Passivhaus buildings are super insulated and extremely air-tight when compared to conventional buildings, reducing the heat flow through the building envelope (walls, roof and floor) and requiring minimal energy to be conditioned (heated, cooled, dehumidified and ventilated). They maintain constant temperatures throughout the year across all building spaces, achieve superior indoor air-quality and have no humidity issues. A Passivhaus design is not just confined to residential buildings but instead applies to any building type and size (e.g. schools, office, supermarket, hospital).
How does it work?
Regardless of the climatic region and season, a Passivhaus can maintain a thermally comfortable indoor environment with low (or zero) energy consumption from fossil fuels. Even in Cyprus, which has a warm climate, a Passivhaus building can achieve year-round comfort without the use of conventional heating and cooling systems. The buildings are conditioned (heated/cooled) passively using solar energy, even under the most extreme conditions. The building also uses internal heat gains (e.g. from people, electrical equipment, lighting) to be heated during winter. Over summer, the cooling load required to maintain the building at comfortable temperatures is reduced by selecting optimal window orientation, providing shading and night-time (natural) ventilation. A mechanical ventilation system with heat recovery can be installed to supply conditioned (warm/cool) fresh air, extract stale air and ensure an excellent indoor air quality. This incurs minimal cost as it utilises the heat from the exhausted air to condition the fresh air and thus the indoor space.
The careful design of the building, and the correct selection and application of the building materials are necessary to ensure that a Passivhaus building to achieve a comfortable indoor environment throughout the year that is cost-effective. The building achieves these properties through:
- super insulate the entire building envelope (e.g. walls, roof, foundations),
- high performance / well-insulated windows and doors,
- air-tight structure,
- absence of thermal bridges,
- optimal use of solar gains (i.e. building orientation, daylight, glazing ratio), and
- mechanical ventilation with heat recovery.
Designing a Passivhaus Building
To achieve a passive design for your building, your architect in collaboration with your energy engineer should integrate the passive design with the architectural design of your building. Further, it is vital to select the most appropriate building materials and equipment (mechanical ventilation, lighting etc.