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Introduction to Passive House

Posted on October 29, 2021

Passive house or Passivhaus is a building standard at the forefront of improving thermal comfort, improving efficiency, and reducing energy use of the building’s we inhabit. It was developed in Germany in the 1990s and has developed into the gold standard for low energy buildings that perform as they were designed, so much so that it is now being adopted by many UK councils as a benchmark for their own new build housing.

So, what is Passivhaus? 

Whilst based on principles of building physics, Passivhaus is a back-to-basics approach that focusses getting the key elements of building design working together to reduce the annual energy use of a building to 15kWh per sqm or lower. For comparison, the typical UK Victorian house uses in the region of 20 x more at 300kWH per sqm and even a modern house will typically use over 6 times more at 100kWH per sqm. 

It is not just for homes, and can be equally applied to any building type. Successful Passive projects in the UK range from bespoke one-off homes, to low cost social housing and even a spa and leisure complex that is currently being built by Exeter City Council about 2 miles from Grainge’s office! 

How it is achieved and some more of the benefits. 

There are some key principles to achieving Passive House

  • Thermal envelope – a layer of insulation wrapped continuously around the house, that is not punctured by numerous elements of structure and does not have weak points at connections e.g. between walls and floors or roof and walls. The ensures that the walls, floors and roofs loose minimal heat through their surfaces. 
  • Airtightness – a Passive House must be highly airtight to avoid energy loss through air leaking out through gaps, measured in ‘air changes’. A Passive House allows 0.6 air changes whereas current UK building regulations allow up to 10. 
  • Ventilation – fresh air is paramount for internal comfort. Passive House’s recover the warmth from warm stale air in the house and put it into fresh air to allow comfortable, draft-free spaces. This is done through mechanical ventilation and heat recovery (MVHR). 

All of the above (and a fair bit more) is put into a building energy model called PHPP (Passive house planning package) and the design can be tweaked until you can demonstrate the building energy gains and losses are within the Passive House Targets. As the model and building process is more involved than required by many elements of standard UK building regulations, the building is much more likely to perform as designed and avoid the ‘performance gap’ – this is where the reality of a building’s energy performance is far worse that its theoretical design. 

Whilst additional renewable technologies can be added to Passive House, reducing the need for energy in the first place is at its heart. Passive House is synonymous with low energy use, low energy bills and high comfort, which addresses some of the key issues associated with climate change, fuel poverty and impact on the UK energy grid. 

Grainge Architects and Passivhaus 

Grainge Architects are members of the UK Passive House Trust and have a certified Passive House Designer recently qualitfied via the UK-leading AECB CarbonLite course. Give us a call if you would like to discuss how we can help you create your own truely low energy building. 

For more information have a look at the Passive House Trust Website: 

https://passivhaustrust.org.uk

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