What makes a Passivhaus so energy efficient?

A Passive House requires as little as 10 percent of the energy used by typical Central European buildings – meaning an energy savings of up to 90 percent.

So how does it work?

  • Passive Houses require less than 15 kWh/(m²yr) for heating or cooling (relating to the living space)
  • The heating/cooling load is limited to a maximum of 10 W/m2
  • Conventional Primary energy use may not exceed 120 kWh/(m²a) – but the future is renewable energy supply (PER) with no more than 60 kWh/(m²a). This is easy to accomplish with passive houses.
  • Passive Houses must be airtight with air change rates being limited to n50 = 0.6/h.
  • In warmer climates and/or during the summer months, excessive temperatures may not occur more than 10 % of the time.

There are 5 principles which inform the design and construction of a passivhaus and help to make it so energy efficient: 

  • High quality insulation and superior windows means that with a building shell consisting of good insulated exterior walls, roof and floor slab, it will keep the heat in during winter in the house – and out during summer.
  • No thermal bridging; the insulation is applied without any “weak spots” around the whole building so as to eliminate cold corners as well as excessive heat losses 
  • Airtight construction 
  • Mechanical ventilation 

These principles are the core ways in which you can differentiate a “normal” home with one that has the PassivHaus badge of approval. Next week we’ll be looking at examples of Passivhauses in Scotland.