London Cooling

The building industry’s voracious appetite for both energy and natural resources has many architects aspiring toward zero waste, zero emissions, and zero grid-sourced energy use in their designs—–but everyone needs a good example to help them achieve their goals. The Lighthouse, a London-area show home, has the potential to make a huge impact on the practice of sustainable architecture because of its minimal impact on the planet.

Designed by Sheppard Robson for the Building Research Establishment (BRE), the Lighthouse bundles together a number of advanced technologies to meet the highest level of the Code for Sustainable Homes—–a new set of sustainability criteria with which all new homes in England must comply by 2016. For instance, the sloping 40-degree pitched roof integrates a photovoltaic array with highly efficient structural insulated panels (SIPs), attractive timber framing, and mechanical ventilation with heat recovery (MVHR) to maintain consistent indoor temperatures. The standard interior layout has also been inverted, with sleeping quarters placed on the ground floor and living areas above. This gives the most heavily trafficked rooms maximum exposure to sunlight through double-height windows and a rooftop light shaft.

Perhaps the most unique feature of the Lighthouse, though, is the windcatcher—–a low-tech passive cooling system that has been around for millennia but rarely appears in new construction. Originally designed and used in Persian oasis cities, the device works like a chimney.

A traditional windcatcher is a vertical void, like an air well, made from brick, stone, or other basic building materials. It cuts down through the center of a house, from the roof all the way to the basement. On each floor of the interior, the windcatcher has shuttered apertures that can be opened or closed as needed, depending on the season. Used in conjunction with windows on the outside of the house, and with doors in the central corridor, a well-operated windcatcher lets residents directly manipulate the flow of air into and out of the home—–and there’s no need to use electricity.This process generates a kind of personal weather system, sending cool breezes out from the center of the house (when the windcatcher pulls cool air down from roof level) or dispersing hot winds upward through the structure (when it sucks hot air up from inside). Activated naturally by gradations in temperature from top to bottom, it’s like a preventative, self-regulating air conditioner.

Windcatchers can also be used in tandem with underground streams. Air passing over the super-cool subterranean water creates chilly residential microclimates; the effect can be so intense that long before the advent of electricity, icehouses could be operated—–even in summer. The Iranian cityof Yazd, for instance, located at the meeting point of two deserts, is famous for its giant windcatching towers, which help to define the city’s skyline. Many of these sit atop domed cisterns, or ab-anbar, in which chilled water can be stored for several seasons. Ice making has been abandoned inside these structures for reasons of bacteria,but indoor reservoirs will always be useful in a desert climate.

Of course, the top end of any windcatcher risks turning into nothing but an inlet for dust and bugs—–and even birds—–but filters and screens can be installed to maintain the divisionbetween inside and outside. Traditional designs also include internal dust sills, which work when the bottom of the shaft is wider than the top, thus slowing down breezes at the base—–and allowing dust to settle.

Windcatchers are surprisingly sophisticated climate-control devices. Many people wonder how our ancestors ever survived without air-conditioning—–let alone without Diet Coke and iPods—–but these low-tech designs are inspiring evidence that living comfortably does not, by necessity, mean living with electricity.

For now, the Lighthouse stands near London, uninhabited, as it undergoes monitoring and research. Unfortunately,in late 2007, the green prototype was found to fall short of the British construction standards for zero-carbon homes. The design itself called for
a building of the highest level of sustainability, but when it came time for construction, airtightness proved challenging in such a unique structure.

If they can work out the kinks, the architects estimate that the Lighthouse’s total energy bills will be only £31 per year (roughly $60), all of which will go toward purchasing wood pellets for the biomass boilers. With this setup in place the building’s electricity will not only be renewable, it will be nearly as free as the wind.