Low-energy houses

Passive House (Passivhaus) is a standard for energy efficient, comfortable, ecological, and affordable buildings which has been developed in the early 1990’s in Germany. The Passive House Standard creators define it as a construction concept.

A Passive House building is much more than “just” a low-energy building. Passive House buildings allow for space heating and cooling related energy savings of up to 90% compared with typical building stock and over 75% compared to average new builds. Passive House buildings use less than 1.5 l of oil or 1.5 m² of gas to heat one square meter of living space for a year – substantially less than common low-energy buildings.

Passive House buildings make efficient use of the sun, internal heat sources and heat recovery, rendering conventional heating systems unnecessary throughout even the coldest of winters. During warmer months, Passive House buildings make use of passive cooling techniques such as strategic shading to keep them comfortably cool.

Passive House buildings are praised for the high level of comfort they offer. Internal surface temperatures vary little from indoor air temperatures, even in case of extreme outdoor temperatures. Appropriate windows and a building envelope consisting of a highly insulated roof and floor slab as well as highly insulated exterior walls keep the desired warmth in the house – or undesirable heat out.

A ventilation system supplies constant fresh air imperceptibly, making for superior air quality without unpleasant draughts. A highly efficient heat recovery unit allows for the heat contained in the exhaust air to be re-used.

Passive House Standard

For a building to be considered a Passive House, it must meet the following criteria:

Space Heating Demand: not to exceed 15kWh annually or 10W (peak demand) per square metre of usable living space.

Space Cooling Demand: roughly matches the heat demand with an additional, climate-dependent allowance for dehumidification.

Primary Energy Demand: not to exceed 120kWh annually for all domestic applications (heating, cooling, hot water and domestic electricity) per square meter of usable living space.

Airtightness: maximum of 0.6 air changes per hour at 50 Pascals pressure (as verified with an onsite pressure test in both pressurised and depressurised states).

Thermal Comfort: thermal comfort must be met for all living areas year-round with not more than 10% of the hours in any given year over 25°C.

Further reading:

Allan Corfield (2017). Beginners’ Guide to Building a Low-Energy Home https://acarchitects.biz/guide-to-building-a-low-energy-home-1/

Passive House Institute https://passivehouse.com/

Passipedia https://passipedia.org/

Passive House Institute (2010). Active for more comfort: Passive House https://www.passivehouse-international.org/upload/Passive_House_Active_for_more_comfort_brochure.pdf