PASSIVE HOUSE PRINCIPLES

Passive house design and construction seeks to work to reduce the energy required to heat and cool a building, by reducing the heating or cooling energy losses in that building. This is called the energy balance. The above video from Tandem Architecture in Canada explains the principle very nicely. 

The five principles of Passive House design are (applicable for Melbourne):

  1. Insulation - higher levels use BCA standards x 150%

  2. Window U values 1.3 - double glazed low e (Passive Haus warm temperate zone)

  3. Heat recovery unit >75% efficiency. Use certified Passive Haus units. Ventilation units consume a similar amount of  energy use as a light globe. Filters to be changed once every 12 months.

  4. Airtightness - Airtightess <0.6 ach (air changes per hour). Design an un-interupted insulation barrier around the building fabric. Junctions of elements are the most challenging locations. Measure with a blower door (pressurisation test). Needs to be <0.6 ach. The AusZEH House achieved 4 ach. Average of Aus houses built in last 15 years 15 ach.

  5. Thermal bridge free design - This is also a new requirement of the BCA 2019. Psi value measures speed of thermal bridging. Psi<0.01W/mk considered thermal bridge free. Design to avoid thermal bridging through timber studs. Add an internal layer for services so these do not bridge the insulation.

In Melbourne this means:

  • 80-90% less energy use than most blgs. Equiv to approx 8.5-9.5 stars

  • Heats or cools required ventilation - no more

  • Heating <10W/m2 Cooling <10W/m2

  • For Passive Haus certification Primary energy (energy required to run everything in the blg incl heating/cooling, HWS, lights, power etc) needs to be <120kWh/m2.annum ie more than just NatHERS.

  • Alternative energy not required under Passive Haus classic accreditation

  • Low area/volume ratio - good to be <0.7 will help

  • No open chimney

  • Lager openings to the sun, smaller away from the sun

  • Use Passive Haus certified components eg certified heat pumps