Donnachadh McCarthy: The Home Ecologist

'Passive houses can cut heating bills by up to 90 per cent and eliminate the need for heating'


Some economists are predicting that the price of oil (and with it gas and electricity bills) could soar from its current high of $125 (£64) up to $200 a barrel within a couple of years. Therefore, promises of reducing heating bills for new homes by up to 90 per cent and eliminating the need to install any type of central heating boiler sound very attractive indeed. This is what is being promised by the energy efficiency experts behind the PassivHaus movement, which was started more than 10 years ago in Germany by Professor Wolfgang Feist.

Essentially the PassivHaus approach says that if you pay very close attention to three core issues – improving the air-tightness of your new building, stopping heat escaping through what they call "heat-bridges" and finally maximising heat gain from the sun in winter and minimising it summer – then you can cut the energy required for heating the house so much that it will not require any traditional central-heating boiler or air-conditioning unit. As they refer to such heating/cooling systems as "active systems", hence the term PassivHaus is used to represent the opposite.

The importance of eliminating heat-bridges is now gaining wide acknowledgement amongst builders and architects. It is the technical jargon for a material that conducts heat from inside a building to the outside, e.g. a metal pipe passing through an insulated wall will carry heat to the outside. The PassivHaus team argue that if you can eliminate such heat-bridges, you can seriously cut heat losses from new buildings.

Likewise, they argue that radically improving the air-tightness of a building will cut energy losses. The standard devised by the PassivHaus Institute calls for a level of air-tightness 10 times better than even the very latest UK building regulations. Recognising that human health requires proper ventilation, the standard calls for the inclusion of whole-house mechanical ventilation with heat recovery. Heat recovery means these ventilation systems use the outgoing stale warm air to heat the incoming fresh air but must be more than 75 per cent efficient to qualify for the PassivHaus standard.

Interestingly, this standard accepts the heat provided by the ventilation system may occasionally need topping up and suggest an integrated hot water, ventilation and electric-heating unit. PassivHaus estimate that a modest 1Kw electric-heater would provide all the extra heating needs of an average house.

This ultra-efficient standard is being introduced to the UK by the Building Research Establishment (BRE) and under the helpful eye of Gavin Hodgson, they provide support and certification for the system in the UK. There are already more than 6,000 such PassivHaus certified buildings across Europe. The first are now under construction in the UK. So the race is on to see who will win the accolade of being the first UK certified PassivHaus.

With the climate crisis now requiring an urgent global "Eco-Marshall Plan", then maybe it is fitting that in a small way, a positive German invasion of the UK could help get that plan off the ground.

For more information, visit

Donnachadh McCarthy works as an eco-auditor and is author of 'Easy Eco-auditing'

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