Passive Houses

Passivhaus is the fastest-growing energy performance standard in the world.

The robust simplicity in its design allows a designer to minimise the building’s heating requirements.

Passive Houses are extremely well insulated and designed to be substantially heated from passive gains such as the sun’s heat. Typically these houses require up to 90% less energy for heating compared to a conventional house.

Examining the Passive House standard in detail, it must meet the following criteria:

  1. The space heating energy demand should be under 15 KWh per square metre of living space per year or 10W per square metre peak demand.
  2. The primary energy demand, the total energy used for all domestic requirements (heating, hot water and domestic electricity) must be less than 120KWh per square metre of floor area per year.
  3. The level of airtightness must be a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50).
  4. Thermal comfort must be achieved during winter as well as in summer, with less than 10% of the hours per year over 25 degrees Celsius.


  1. Thermal bridge free design: By planning and executing all edges, corners, connections and penetrations with great care, thermal bridges can be avoided. Where they cannot be avoided, they should be minimised as much as possible.
  2. Superior windows: The window frames must be well insulated and fitted with low e-glazings filled with argon or krypton to prevent heat transfer. For most cool-temperate climates, this means a U-value of 0.80 W/(m²K) or less, with g-values around 50% (g-value = total solar transmittance, proportion of the solar energy available for the room).
  3. Ventilation with heat recovery: Efficient heat recovery ventilation provides good indoor air quality while saving energy. In a Passive House, at least 75% of the heat from the exhaust air is transferred to the fresh air entering the house through a heat exchanger.
  4. Quality insulation: The exterior of the house must be extremely well insulated. For most cool temperate climates, this means a heat transfer coefficient (U-value) of 0.15 W/(m²K) at the most, i.e. a maximum of 0.15 watts per degree of temperature difference and per square metre of exterior surface are lost.
  5. Airtight construction: Uncontrolled leakage through gaps must be smaller than 0.6 of the total house volume per hour during a pressure test at 50 Pascal (both pressurised and depressurised).

Cygnum have a wealth of experience of working on Passive Houses and are the only Irish company and one of only two between Ireland and the UK to have a Passivhaus system – a methodology for designing a Passive House – certified by the Passivhaus Institute in Germany.

Our team of talented specialists includes two highly qualified designers who have passed the rigorous exams set by the Passivhaus Institute and are experienced in the design, engineering and on-site phases of both residential and large commercial projects.

Our Passive House experience permeates all aspects of our business from engineering and design through to on-site installation thereby providing a seamless experience as part of our dedicated customer service.

If you’d like to contact us, one of our team will be happy to answer any questions you have or to discuss your ideas for your dream home or your next project.