What is a Passive House?
The gold standard of energy efficiency
Why choose Passive House?
The Passive House standard provides many benefits. Here are just a few:
- Energy efficiency - Passive House buildings require no central heating and use up to 90% less energy for heating and cooling than traditional buildings, resulting in significant energy cost savings.
- Comfort - Passive House buildings provide superior sound insulation, consistent indoor temperature, and they are free of draughts and cold spots, resulting in improved comfort for occupants.
- Health - Mechanical ventilation provides a continuous supply of fresh air while recovering heat from the exhaust air, resulting in improved indoor air quality.
- Durability - Airtight building envelope and thermal bridge-free design of Passive House buildings result in a longer building lifespan and reduced maintenance costs.
- Sustainability - Passive House buildings have a smaller environmental footprint during the use phase than traditional buildings, as they require less energy to heat and cool.
Cost of building a Passive House
There has been a consistent downward trend in costs as the standard has become more widely adopted. Passive Houses tend to cost approximately 4–10% more than traditional houses, but the initial investment is offset by the energy efficiency, which may translate into up to 90% savings on heating bills.
Moreover, investing in the quality of a building confers many other benefits such as lower maintenance costs, higher worth in the housing market, higher comfort, and more.
Passive House walls
Exterior walls are a key component of creating a well-insulated envelope.
Here are some of the parameters to be considered:
- Continuous insulation with no thermal bridges
- An easy to apply airtight layer
- High thermal mass (in some climates)
As a rule, the walls of Passive Houses are thicker than that of regular buildings.
Typical options for high-performing exterior walls include:
- SIP - Insulating foam core sandwiched between two structural facings
- Concrete or brick walls insulated with polystyrene or mineral wool
- Light timber constructions insulated with glass wool or blown in fibres
While all viable, some alternatives are better than others. Synthetic or mineral-based materials have typically a higher carbon footprint and come from non-renewable sources.
Bio-based materials can offer the same level of energy-efficiency, while leaving a minimal environmental footprint. Straw has an impressive thermal conductivity value of 0.06 W/mK. It is a rapidly renewable resource and has the lowest embodied energy of all insulation materials.
Passive House wall details
With the core aspects of Passive House established, let us explore the structure of an ideal Passive House exterior wall component.
The core of the EcoCocon wall system are load-bearing timber-straw panels. An airtight membrane is fixed onto the exterior side and covered with fibre board. Our innovation – using a vapour-permeable membrane as an airtight layer on the exterior side – has been confirmed by WUFI calculations and field tests to work in nearly all climatic conditions.
Applying the membrane on the exterior makes it extremely easy to achieve great blower door test results. Typically below 0.3 h-1 on the first attempt. The membrane also doubles as temporary weather protection until the facade is complete. Moreover, protected by the straw wall, the membrane is safe from being punctured during construction.
In addition, not having to deal with the airtight layer on the inside makes it possible to apply the clay plaster directly onto straw.