Heard of the Passivhaus concept? Discover why more and more architects and designers are using its techniques to build the sustainable housing of the future.
Passivhaus recently hit the housing headlines when Goldsmith Street in Norwich was named the 2019 winner of the prestigious Royal Institute of British Architects (RIBA) Stirling Prize. When crowning the development as the best new building in the UK, RIBA judges said it “meets rigorous Passivhaus environmental standards”.
What is the Passivhaus concept?
There are five guiding principles:
- Superior windows
- Airtight construction
- Ventilation with heat recovery
- Quality insulation
- Thermal bridge free design.
The first Passive House was built in Darmstadt, Germany in the early 1990s. Now the city is home to the Passive House Institute, which promotes the construction of buildings which combine a high level of occupant comfort with low energy heating and cooling.
“The heat losses of the building are reduced so much that it hardly needs any heating at all,” says Prof Dr. Wolfgang Feist, head of energy-efficient construction/building physics at the University of Innsbruck, Austria and director of the Passive House Institute.
“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.”
The Passivhaus standard
To be certified as a Passive House, a building needs to meet strict criteria. The aim is to create a building in which “thermal comfort is achieved solely by post-heating or post-cooling the fresh air flow required for a good indoor air quality, without the need for additional recirculation of air”.
There is also the EnerPHit standard – which applies to refurbishment projects. EnerPHit is a slightly relaxed code for when the existing architecture and conservation issues mean that meeting the Passivhaus standard is not feasible.
Why are the Passivhaus benefits?
Compared to the UK’s current new home standards, Passivhaus buildings achieve a 75% reduction in space heating requirements. The concept can therefore be used to achieve the 80% carbon reduction target set out by the Government.
According to the Passive House Institute, evidence shows that Passivhaus buildings are performing to standard. This is crucial as the discrepancy between design aspiration and actual performance for many new buildings in the UK can be as much as 100%.
The Goldsmith Street project
In 2008 the city of Norwich held an international RIBA competition to choose architects for the scheme, which was won by Riches Hawley Mikhail. However, the financial crisis put the project on hold and the city took the bold decision to develop the site itself, without a housing association or development partner.
The brief was to provide approximately 100 new homes consisting of about 50 individual houses and 50 flats. The design seeks to re-introduce streets and houses in an area of the city which is dominated by 20th century blocks of flats.
From the outset, Goldsmith Street was designed as a low-carbon scheme, where all homes face south to “maximise solar gain” while each wall is more than 600 millimetres thick. Other measures to increase insulation include letterboxes being installed in external porches, rather than doors to minimise draughts.
The project is on target to achieve full Passivhaus certification — the city claims it would be the largest social housing scheme in the UK to achieve the standard.
The benefits for residents include sunny, light-filled homes with low fuel bills of approximately £150 per year. In the main, these properties will be socially rented.
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