What is a Passive House?

The 5 Key principles.

Passive House works around 5 key principles:

  1. Airtightness

  2. Thermal Insulation

  3. Heat Recovery Ventilation

  4. Thermal-Bridge-Free Design

  5. High performance window

Using these 5 key principles we are able to produce a house that offers a controlled environment that is able to hold a comfortable temperature year round with minimal input from a heating and cooling system.

Studies have shown that more than 40% of Australian homes have condensation issues. With condensation comes an increased risk of mould. In a passive house calculations are made using PHPP (Passive House Planning Package) to design the home so that it remains within a safe and comfortable temperature. Testing has found this to be 20-25°C and a relative humidity of 60% at 25°C. With a controlled climate and no surface temperatures lower than 12.6°C (due to thermal-bridge-free design) we know that the risk of condensation, and therefore mould, is mitigated.

© copyright Passive House Institute 2015

PASSIVE PRINCIPLES

  • Airtightness

    Unlike a conventional home, a passive house is designed to be completely airtight. To achieve this we use tried and tested products by leading brands for all external windows and doors, as well as installing an airtightness membrane on the internal of the building’s thermal envelope.

    The airtightness layer should be on the side of the envelope that is warmest for the longest period per year, in Melbourne this is the interior of the house.

    To achieve Passive House we must reach an airtightness level of 0.6 ACH at 50 pascals. This is tested using a blower door test, where a fan is placed on the front door opening and the house is then pressurised and depressurised to measure the air tightness. We perform this test while we are still able to access the airtightness system so that if there are any major leaks we are able to access them.

    Image © Passive House Institute

  • Thermal Insulation

    Thermal insulation is extremely important for stopping unwanted losses or gains of heat. In passive houses we use location-specific data to determine the requirement of our insulation. in Melbourne we roughly require 140mm of insulation to achieve our thermal value needed.

    Our insulation layer needs to be continuous and complete, encompassing the entire perimeter of the building.

    Image © Passive House Institute

  • Heat Recovery Ventilation (HRV)

    HRV is another component that is not seen in conventional builds. Due to the building being airtight, fresh air needs to be supplied to the building. This could be done by opening doors and windows however, this air isn’t conditioned and if the external temperature is not around the comfortable 20-25°C range.

    HRV units work 24/7 to replace the air in the house with fresh air from inside. As the internal extract air passes through the system, it recovers the heat from the air and transfers it into the external supply air.

    The external supply air also passes through a filter, reducing allergens, dust and pollutants entering your home.

    Image © Passive House 2023

  • Thermal-Bridge-Free Design

    Being thermal-bridge-free allows for lower heat transfer and controlled internal temperatures. Thermal bridges are weak points within our thermal envelope. without thermal bridges, the risk of condensation on surfaces is reduced, as external temperatures can’t transfer to the interior causing cold spots.

    Image © 2018 International Passive House Association

  • High Performance Windows

    All openings for doors and windows are the weakest points in our insulation and airtightness layers. High-performance windows are extremely important as they are designed to allow lower air leakage and lower unwanted thermal gains and losses.

    All high-performance windows are either double or triple-glazed and are constructed of low-conductivity materials or are thermally broken.

    Image © 2023 NEUFFER WINDOWS + DOORS, KRONPRINZSTRASSE 8, 70173 STUTTGART, GERMANY