Given the hullabaloo about wind turbines, heat pumps and photovoltaics, you’d be forgiven for thinking that alternative energy in architecture is entirely dependent on gizmos and gadgets. But as Howard Liddell of Gaia Architects (www.gaiagroup.org) in Edinburgh, Scotland, bluntly puts it, ‘True alternative energy is not to use it’.
This would seem obvious to our forbears. In the past, when respect for natural resources was instinctive, buildings and their occupants were necessarily energy-efficient. Today, as Piers Smerin of Eldridge Smerin Architects and Designers (www.eldridgesmerin.com) points out, ‘with 30% of all UK delivered energy currently being used on domestic heating, this far outweighs other energy uses and makes producing a house with low energy the key environmental issue’.
‘We can quite easily design houses and other buildings that require zero heating. I am currently designing a “Weetabix” School,’ Liddell continues jokingly, meaning that, ‘the heating system is the pupils via the energy they are giving off as a result of their hearty breakfast’.
He estimates this to be 100W per child. ‘The problem in a technic al-fix society is that we look for technical-fix solutions – the opportunity to be a non-consumer gets lost in the rush for innovative technology,’ he surmises.
‘The first rule in an energy strategy for a building should be to remove the need for energy consumption as far as is reasonably possible. This may seem obvious but I have yet to see a building with a photovoltaic system in the UK, which has been super-insulated and was tested for airtightness. Then, the only energy supply home owners have to find is for hot water and, of course, electricity,’ states Liddell.
He categorises his approach as ‘eco-minimalism’ or, more simply, ‘good housekeeping’. It is a method also described as passive design or natural heating and cooling – creating buildings in which a comfortable indoor climate can be achieved in summer and winter without recourse to conventional heating or air- conditioning systems. Passive design has a role to play in every climate; utilises both ancient and modern materials, from argon-filled triple glazing to rammed earth walls; and is increasingly implemented, as a matter of course, in both new builds and refurbishments in many countries, but not yet in the UK where residents have become disconnected from the practicalities of energy generation and conservation.
‘People can understand that a gadget provides them with electricity but don’t necessarily understand the principles behind maximising heat gains or minimising heat losses,’ suggests Dan Gibbons of Bere Architects (www.bere.co.uk), a London practice that bucks the trend, even incorporating passive energy in their renovation projects, for instance at Sylvanus House in north London. ‘Taking on board passive principles is more about lifestyle. If you leave windows open during the day in summer then the house is going to heat up. It seems anathema to us to close windows, or use shutters, although people on the continent have been doing that as a matter of course for centuries,’ he continues.
The irony is, the finances of renewable energy often don’t add up. ‘Until a building is properly insulated and made airtight with ventilation heat recovery [to remedy the resultant humidity and pollution], eco-gimmicks are really looking like a very bad deal in terms of value for money,’ states Liddell. ‘An array of photovoltaic cells to supply 5kW of electricity [note a kettle uses 2kW; a power shower 7–9kW] will set you back at least £20,000 and take 50 years to pay back. With the snag that they lose efficiency at about 1–2% per annum so they never really last 50 years before they need replacing.’Leaving aside the ‘Weetabix’ effect, the five key considerations in passive design are orientation, insulation, airtightness, shading and landscaping. Orientation boils down to positioning the building to maximise solar heating in winter and minimise overheating in summer.
Insulation, predictably, comes down to reducing unwanted conductive heat loss. Airtightness, contrastingly, relates to infiltration losses that result from an inadequately sealed structure. (The infiltration rate on a typical house is around 1.5 air changes per hour; with care it can be reduced to just 0.2 air changes per hour.) Shading prevents overheating, while landscaping contributes to shading in the summer and wind protection in winter....