Architecture
Life Without Air Conditioning? These Passively Cooled Homes Say Yes
Ever wish you could chuck that money-sucking air conditioner? Check out these homes that keep the air cool and flowing passively
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:
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.
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.
Both of these houses from the "From the Ground Up" competition and book were designed and built to passive-house goals; like BedZED, passive houses use very tight envelopes and heat-recovery units. The house on the right, named TED, is one story taller than its silver neighbor, something that we'll see it uses to its advantage.
Openings in the upper floors allow the interior to act like one big chimney. The pop-up that caps the house has a south-facing window that heats up this zone, helping to draw warm air up and out of the house.
A good place to look for innovative solar designs (relevant here, considering that all passive strategies are part of solar design, given the sun's role in temperature, wind, rain etc.) is the biennial Solar Decathlon. Traditionally the participating schools would build a house on the National Mall and compete against one another to make the most cost-effective, energy-efficient and attractive house possible. This year it is being held in Irvine, California.
This entry by Appalachian State University is called Homestead; it embraces the traditional Appalachian lifestyle in its plan and outdoor spaces. The porch covers 900 square feet of outdoor space between the house and flexible modules that can be added as needed. The roof of the porch provides energy for the house through PVs, and the shaded outdoor space is an important part of the house's cross-ventilation strategy.
This entry by Appalachian State University is called Homestead; it embraces the traditional Appalachian lifestyle in its plan and outdoor spaces. The porch covers 900 square feet of outdoor space between the house and flexible modules that can be added as needed. The roof of the porch provides energy for the house through PVs, and the shaded outdoor space is an important part of the house's cross-ventilation strategy.
One of the unique aspects of ASU's design is a modern-day trombe wall (typically a thick wall fronted by a glass wall that stores heat during the day and releases it at night) that occupies the window fronting the house. Part of the window is vertical fins with a phase-change material; they accomplish the same thing as a larger trombe wall, all the while acting like a window and allowing views out. This photo shows that a sliding panel can be moved in front of the window, so that the fins do not get hot; this makes sense on hotter days, when the release of heat at night is not desired.
The simple and open interior (with a nice single-wall kitchen, no less) benefits from cross ventilation from the shallow depth of the plan and the corridors on both sides of the kitchen leading to the bedrooms.
When the doors to the bedrooms are open, accompanied by the exterior doors on either end of the house, the interior's cooling benefits from generous cross ventilation.
This house in Santa Cruz, California, exhibits a couple of strategies from the outside: shading of south- and west-facing windows through trellises and towers that are used for ventilating warm air. These linked elements work well with the larger design, which has an organic quality, as if the house has evolved piece by piece over time.
From the inside we can see how the corner pops up above the roof. This section, the tower, helps to ventilate warm air.
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.
The BK House's tall spaces also help to ventilate warm air. Here we can see an operable vent in the translucent panels at the top of the living space.
The BK House's tall spaces also help to ventilate warm air. Here we can see an operable vent in the translucent panels at the top of the living space.
A master at dealing with the hot climate of Australia is Glenn Murcutt, an architect who is inspired by traditional architecture but executes projects in contemporary materials. In the case of the Simpson-Lee House, the metal, concrete and masonry respond to the fire risks in the area, but the exterior provides plenty of natural ventilation for cooling the interior.
The eastern elevation includes a generously cantilevered roof above clerestory windows that sit atop sliding glass panels that open up the whole living area to the elements.
Murcutt actually likens the experience of the open east facade to looking out from a cave, even though the well-insulated walls are rather thin, the house is raised above the landscape and the view is through a metal frame.
More: If Walls Could Talk: Back to the Future of the House
More: If Walls Could Talk: Back to the Future of the House