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Blog Post 13 June 2019

Passivhaus: what you need to know

Passivhaus, literally passive house in English, refers to buildings created to rigorous energy efficient design standards so that they maintain an almost constant temperature. Passivhaus buildings are so well constructed, insulated and ventilated that they retain heat from the sun and the activities of their occupants, requiring very little additional heating or cooling.

The Passivhaus Institute in Germany developed the energy efficient building principles, following a research project to investigate why low energy buildings often didn’t deliver on their expected energy saving potential. Builders of energy efficient homes and buildings can apply to have their buildings certified by the Passivhaus Institute. To achieve the certification, you must use the specific Passivhaus planning system, which allows you to adjust your design until your property reaches the required energy efficient standard.

While we’re not all in the position of creating a new home from scratch, we can apply the principle of reducing energy demand in our homes through energy efficient design to older homes too. Find out more about insulating your property or read on for more about how Passivhaus buildings function.

Carbon neutral vs Passivhaus

The methodology behind a Passivhaus building differs from some carbon neutral buildings, which use a combination of energy efficiency and clean energy generation to offset any energy use. A Passivhaus building aims not to use as much energy in the first place by being effectively sealed against the elements.

The actual construction methods of Passivhaus buildings will vary but they will all have some features in common, including:

  • far greater insulation than typical UK properties
  • triple glazing, with insulated frames
  • impressive airtightness levels (around 20x more than a standard build)
  • mechanical ventilation, with heat recovery system attached.

Heating a Passivhaus

A Passivhaus building aims to reduce the need to heat the building to such an extent that you don’t need a conventional heating system. However, there will be some heating mechanism attached to the property – often it takes the form of a small heating element attached to the ventilation system. These use very little energy and usually only kick in once the outside temperature drops below freezing. A passive house will also need to have a mechanism to heat water – it could be solar heating, perhaps coupled to a conventional gas boiler.

Where can you find Passivhaus buildings in the UK?

You can find Passivhaus developments in pockets all over the UK. The current largest residential Passivhaus development is located in Plymouth, according to the Passivhaus Trust. Primrose Park, a development of 72 houses, came about because the land was too costly for commercial developers to build on. As a result, the council offered the former school site to affordable housing developers for a token £1 as part of a programme of activity to ‘Get Plymouth Building’.

Energy costs are so low for tenants of Passivhaus properties that they’re far less likely to default or get into arrears with their rent. Hastoe Housing Association, reports that rent arrears are virtually zero on its Passivhaus development, compared to a 3-4 per cent rate generally across its stock.

Spending less on energy and reducing householders’ financial struggles seems a logical connection, but it’s not something commercial operators have focused on to date.

Why aren’t all buildings constructed to this standard?

The super energy-efficient Passivhaus building technique has higher up-front costs, which deters commercial operators. However, it has significant cost-saving and energy security implications for years to come – something that is of significant interest to local authorities, housing associations and individuals who are particularly motivated to create sustainable buildings.

You can retrofit older properties so that they function along the same principles, although it’s not usually possible to reach the same levels of insulation as a specially designed property. The Passivhaus Institute does have a separate certification that recognises appropriate retrofitting work, which has a lower threshold than for a full Passivhaus building as a result.

Certainly if the UK is to reach its carbon reduction targets, it will need to apply some of the lessons from Passivhaus buildings to the wider housing stock. While most of us are unlikely to be able to create fully functioning Passivhaus type buildings, we can insulate and ventilate our homes effectively, to ensure that they are as energy efficient as possible.

More on this…