PASSIVE BUILDS

5 PASSIVE HOUSE PRINCIPLES

1. Thermal Insulation

Opaque building components of the exterior envelope of the house must be very well-insulated. For most warm-temperate climates, this means a maximum heat transfer coefficient (U-value) of 0.03W/(mK), i.e. a maximum of 0.15 watts per degree of temperature difference and per square metre of exterior surface are lost.

2. Passive House Windows

The window frames must be well insulated and fitted with low-e glazing’s filled with argon or krypton to prevent heat transfer. For most warm-temperate climates, this means a U-value of 0.90 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 Heat Recovery

Heat recovery ventilation allows for quality indoor air and saving energy. In Passive House, at least 75% of the heat from the exhaust air is transferred to the fresh air by means of a heat exchanger.

4. Airtightness of the Building

Air leakage average must be smaller than 0.6 air changes per hour of the total insulated envelope area during a blower door pressure test of 50 Pascal (pressurised and depressurised).

5. Thermal Bridges

All edges, corners, connections and penetrations must be planned and executed with great care so that thermal bridges can be avoided. Thermal bridges which cannot be avoided must be minimised as far as possible.

WHY BUILD A PASSIVE HOUSE?

CUTTING ASTHMA WITH PASSIVE HOUSE BUILDINGS

Comfort

Without the use of mechanical heating or cooling the house is designed so that every room stays around 18°C – 20°C, no matter if it’s -5 or 35°C outside. It will be warmer in winter and cooler is summer. It will also be quieter due the higher insulation and the better-quality windows.


Health

A heat recovery unit will filter and purify the air by reducing carbons and pollen. Using a heat recovery unit will also remove moisture and odours from your home, leaving it fresh and comfortable.

Sleep will be better because the heat recovery unit will reduce carbon dioxide building up in your bedrooms. While sleeping in a closed room, carbon dioxide levels rise very quickly (see graph). In an ideal world, you should be sleeping with both your window and door open to elevite the affects of excessive CO2 exposure. However, in winter (in a standard build) your options are limited as opening a window will reduce the room temperature (which also has negative effects – adults should be sleeping in a room with a temperature of 18°C and infants / elderly should be sleeping with a room temperature of 20°C).

The heat recovery unit reduces the need to open windows for air flow and maintains a comfortable (and healthy) temperature at least 90% of the year (Passive House standard).

CO2 level chart for air quality.
Graph of CO2 levels for 2x Adults and 1x baby sleeping in a 4 x 4m bedroom.

Economical Benefits

By building a Passive House, you will no longer have to constantly heat or cool your home at high costs. The home will be designed around the solar gains and loses specific to your site and it’s orrientation. By applying the 5 Passive House Principles, the need for heating and cooling will be reduced.

“The 2018 NZ Census results showed that 318,891 homes were affected by damp – more than the total number of occupied private dwellings in the Canterbury and Otago regions combined

STATS NZ

Passive House Requirements


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

The Space Heating Energy Demand is not to exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand.

In climates where active cooling is needed, the Space Cooling Energy Demand requirement roughly matches the heat demand requirements above, with an additional allowance for dehumidification.

The Renewable Primary Energy Demand (PER, according to PHI method), the total energy to be used for all domestic applications (heating, hot water, and domestic electricity) must not exceed 60 kWh per square meter of treated floor area per year for Passive House Classic.

In terms of Airtightness, a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50), as verified with an onsite pressure test (in both pressurized and depressurized states). 

Thermal comfort must be met for all living areas during winter as well as in summer, with no more than 10% of the hours in a given year below 18°C or over 25 °C.

All of the above criteria are achieved through intelligent design and implementation of the 5 Passive House principles: thermal bridge free design, superior windows, ventilation with heat recovery, quality insulation and airtight construction.

Our buildings are planned, optimised and verified with the Passive House Planning Package (PHPP).

Using the maths & physics built into the PHPP we calculate the performance of our buildings before completing the design portion of the project and before starting the build.

FREE MUST HAVE E-BOOK!

Your Home, Our Planet” is filled with everything you will want to know before building an Energy Efficient / Passive House. Download the E-Book now, for free!