The Passive House Standard
Passive Houses are the best energy efficient design strategy using conventional building components; outperformaing all regulatory standards.
The basic theory is to reduce the heating and cooling needs of the home, so that one harldy needs to produce any heating or cooling to meet this tiny demand.
In the construction process of a Passive House, greater attention is given to how the building is assembled: no gaps in the insulation; no pipes in the exterior walls; no thermal bridges (a building component that assists heat energy getting from the exterior to the interior or vice-versa); insulation levels are typically double legislation requirements, depending on exact climate; attention to window types, sizes and locations on the envelope; etc.
Additionally, before insulation gets installed, it is recommended to do a blower door test, to understand how air-tight the shell is.
This provides the opportunity to seal up any areas where you can hear and feel air rushing in.
Then with insulation and drywall, the air-tightness gets even better - this is not done with conventional home building.
Because of the attention to detail, a Passive House is typically higher in quality.
"The heat losses of the building are reduced so much that it hardly needs any heating at all. Passive heat sources like the sun, human occupants, household appliances and the heat from the extract air cover a large part of the heating demand. The remaining heat can be provided by the supply air if the maximum heating load is less than 10W per square metre of living space. If such supply-air heating suffices as the only heat source, we call the building a Passive House."
Univ. Prof. Dr Wolfgang Feist
Head of Energy Efficient Construction/Building Physics at the University of Innsbruck, Austria & Director of the Passive House Institute, Darmstadt, Germany
The Passive House Standard requires:
A maximum space heating and cooling demand of less than 15kWh/m2/year or a maximum heating and cooling load of 10W/m2 .
A maximum total primary energy demand of 120kWh/m2/year.
An air change rate of no more than 0.6 air changes per hour @ 50 Pa.
To achieve the Passive House Standard in the UK typically involves:
Very high levels of insulation
Extremely high performance windows with insulated frames
Air-tight building fabric
'Thermal bridge free' construction
A mechanical ventilation system with highly efficient heat recovery