Making homes better for the climate, your wallet and health

Passivhaus homes at Wimbish, Essex. Mark Baigent

In the UK, a third of all the energy used goes towards heating buildings and providing hot water, most of this, a quarter of the total, in homes.

The thermal efficiency of UK homes has increased by one third since 1970, but the average energy used to heat a home has not dropped. In 1970, before the introduction of widespread central heating, homes were colder and many rooms often unheated. Now, occupants heat their homes more uniformly and to a more comfortable temperature. Heating accounted for as much as two-thirds of total household energy consumption according to 2008 figures; adding hot water provision brings this proportion to over four-fifths. Mainly, the fuel used to heat homes is gas.

This is why there’s so much concern about fuel prices today. The average domestic fuel bill in the UK in 2012 was nearly £1,300 a year, £800 for gas and £479 for electricity. These prices have doubled in real terms in the past decade due to rises in the price of gas.

Rising energy costs hit the less affluent especially hard. The UK has the highest rate of fuel poverty, and among the highest rate of excess winter deaths in western Europe. The principal cause of this is the poor energy efficiency of Britain’s housing stock.

We really are at a fork in the road. Either we scratch around for new supplies of fossil fuels with the environmental damage they will cause, and prices likely to continue to rise, or we reduce our demand for gas.

There is massive potential to reduce energy use by making homes more energy efficient. If we build new homes and convert existing homes to be very energy efficient we can cut the energy needed to heat our homes by up to 90%.

Isn’t this what the government already has in hand, with Zero-Carbon Homes from 2016, and the Green Deal established to help home owners improve the energy efficiency of existing homes?

Sadly no. The energy efficiency standard used in the so-called Zero Carbon Homes was chosen according to industry concerns in 2009, not to what might be possible or desirable in 2016. We could do much better when building new homes now. The Green Deal is a piecemeal approach to improving the performance of older homes. It does not take a whole-house approach nor examine the fabric of the house in detail, and really can only provide assistance with a few, limited aspects of making a home very energy efficient.

In fact, things are far worse than these building codes and standards indicate. The quality of construction in the UK is such that homes and buildings are far less energy efficient than their designs might suggest.

This means that not only are new buildings likely to be leakier and less energy efficient than claimed, it also means newer, more air-tight buildings pose risks of poor indoor air quality due to sub-standard ventilation. We’ve analysed these quality problems, and suggested some ways in which they can be solved in a detailed report. In particular, good teamwork throughout the whole process is essential, design must be finalised before construction begins, attention to construction detailing is essential, and there must be much more evaluation of performance post-construction.

The housing crisis in the UK is due to a shortage of homes, but if we continue to build homes in the way we do at present then there will be a second housing crisis: a disastrous legacy spanning many decades of higher bills, poorer health, and missed climate change targets.

Gas use for Passivhaus homes at Wimbish compared with the UK average, from data collected by Martin Ingham of Linktreat Ltd since the homes were first occupied. Martin Ingham/Linktreat Ltd

There is, however, an alternative approach that is gaining wide interest because the quality issues are eliminated and heating needs are minimal. We can build new homes to the Passivhaus standard, and refit many older homes to the Passivhaus EnerPHit standard.

The Passivhaus concept was developed in Germany more than twenty years ago and now there are tens of thousands of Passivhaus buildings in Europe and across the world. For a building to be certified as a Passivhaus building, it must be designed to achieve a very demanding standard of energy efficiency to the point that a conventional heating system is no longer necessary. This standard must be demonstrated to be achievable through a computer modelling package, and the quality of construction must be guaranteed through detailed checks and air-tightness testing. Air quality inside the home is maintained with mechanical ventilation with heat recovery: one mechanical fan extracts stale air from the building, while a second provides fresh filtered air. Heat losses are minimised by a heat exchanger transferring the warmth from the outgoing to the incoming air.

The residents of new Passivhaus homes built at Wimbish in Essex found their gas bills reduced by almost 90% compared to the UK average (see figure above), and enjoyed excellent internal air quality and comfortable temperatures year round. In contrast to the unhappy trend for many new homes in the UK that fail to provide adequate space inside or outside the home, Passivhaus homes make maximum use of space because there are no radiators on walls or cold draughts near windows. As one Wimbish resident said: “The houses are so light and spacious”.

We know from the experience at Wimbish and from other Passivhaus projects that construction costs for new Passivhaus homes need be only a few per cent more than for a conventional home and, with good design, perhaps no more at all. Lifetime costs will be far, far lower. If every housing association had similar ambition to Hastoe Housing, the developers of the Wimbish project, there would already be 50,000 Passivhaus homes in planning across the UK. That number would be utterly transformative.