“Capturing passive energy such as light and warmth from the sun is important in addressing the rising costs of energy, the depletion of finite resources and the projected long-term effects of carbon emissions.
Using the sun to light a home is one strategy; others worth considering include passive cooling and ventilation. Living without air conditioning is unimaginable for many people, but given the right design, planning and house orientation, it should be possible to live without the need for mechanical cooling by:
- Cutting down on direct sunlight in warm months
- Drawing warm air out of the interior
- Tightening the envelope to keep heat from infiltrating
- Designing spaces that keep the air cool in the “occupied zone”
BedZED (Beddington Zero Energy Development) is billed as “the U.K.’s largest mixed-use, carbon-neutral development,” completed in 2002. A number of features (a biomass combined heat and power plant, onsite sewage treatment and a rainwater recycling system, to name just a few) are used in pursuit of this goal, but it’s the natural wind-driven ventilation that steals the show. Topping the buildings are rows of wind cowls, which — like the chimneys of yore — give the development a distinctive (and colorful) profile across the sky.
The cowls serve two needs: ventilation and heat recovery. With the cowls no energy is required for ventilation, and in the colder months the heat kept in the house by the supertight envelopes is not lost in the process. The British Isles may not need air conditioning like, say, Florida, but the architects and engineers still had to address cooling.
For one, internal heat gains from computers and other equipment in the north-facing work spaces (living spaces in the mixed-use development face south) are addressed through vents and the building’s thermal inertia. The latter means that the buildings’ roofs and walls absorb the heat from the equipment as well as a good deal of the outside heat in warmer months, therefore minimizing temperature swings between the day and night. After the sun goes down and the temperature drops, the built-up heat is released.
The BK House in upstate New York has a number of sustainable features, including a reliance on passive cooling (no air conditioners).
The exterior, as with other examples, has a supertight envelope with a high R-value. As well, polycarbonate panels, skylights and well-placed windows bring in plenty of natural light.
It’s worth pointing out that passive daylighting is a means toward passive cooling (considering the light entering is not too direct, so it doesn’t lead to heat gain). Every light turned off during the day cuts down on the cooling that would have been required to offset its heat.”