In a world ever concerned with reducing its ecological footprint, the German Passivhaus (“passive house”) standard – and similar building codes such as the Swiss MINERGIE-P – are gaining increasing attention from architects, developers, housing associations and government departments.
When developers adhere to the strict Passivhaus standard, it results in ultra-low energy buildings. The standard has been successfully applied to residential buildings, schools, supermarkets and offices. While it is primarily used in new buildings, it can also be applied to refurbishments.
Most Passivhaus buildings have been constructed in Germany, Austria and Scandinavian countries.
In the UK, the standard has been used in a number of developments, including Agar Grove Phase 1A in Camden, which when complete will be Britain’s largest Passivhaus development. It has also been used in a number of educational buildings, including STEM in Bradford and Stebon Primary School.
Compared to conventional constructions, Passivhaus buildings must be extremely airtight. According to Wikipedia, structures must adhere to “either 0.60 ACH50 (air changes per hour at 50 pascals) based on the building’s volume, or 0.05 CFM50/sf (cubic feet per minute at 50 pascals, per square foot of building enclosure surface area).” To this end, the generally accepted best practice is to test the structure’s air barrier enclosure using the “blower door” method. Ideally, this should be done at the mid-point in construction.
The Passivhaus standard was created so most of the air exchange with the outside occurs by controlled ventilation via a heat-exchanger. This reduces heat loss (or gain, depending on the local climate) to the lowest possible level. Another reason for this arrangement is that Passivhaus requires a great deal of insulation, which can bring challenges with condensation/dew. Control of moisture is made possible through air barriers, and the effective sealing of construction joints and service entry points.
Meeting the Passivhaus standard also involves:
As mentioned, the Passivhaus standard has been used in a number of UK residential, commercial and educational buildings. While some evidence suggests construction the UK and other northern European countries is significantly more expensive compared to central Europe, ultra-low energy bills and minimal CO2 footprint means it could be an increasingly common building standard in the UK.
And of course, air tightness testing plays a critical role in ensuring the standard is met.
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