I went to visit a new ‘PassivHaus’ in Hornsey. It is a terraced house belonging to Metropolitan Housing Association in a conservation area which has been retro-fitted to meet the Passivhaus standards
From the PassivHaus website the following is a description of a dwelling that achieves the PassivHaus standard and typically includes:
– very good levels of insulation with minimal thermal bridges well thought out utilisation of solar and internal gains
– excellent level of airtightness
– good indoor air quality, provided by a whole house mechanical ventilation system with highly efficient heat recovery
By specifying these features the design heat load is limited to the load that can be transported by the minimum required ventilation air. Thus, a PassivHaus does not need a traditional heating system or active cooling to be comfortable to live in – the small heating demand can be typically met using a compact services unit which intergrates heating, hot water and ventilation in one unit (although there are a variety of alternative solutions).
For Europe (40o – 60o Northern latitudes), a dwelling is deemed to satisfy the PassivHaus criteria if:
the total energy demand for space heating and cooling is less than 15 kWh/m2/yr treated floor area;
the total primary energy use for all appliances, domestic hot water and space heating and cooling is less than 120 kWh/m2/yr
These figures are verified at the design stage using the PassivHaus Planning Package.
As the Hornsey house was a retrofit rather than a new build – the standard is marginally different.
It was very impressive – and very warm. Between insulation, special air circulation, triple-glazing, special door fittings and solar panels – it is an example of what can be done where there is a will to actually take the measures that will enable our housing to become environmentally neutral.