Passive solar cuts energy use by 50%
The beauty of harvesting the sun’s heat with a passive-solar house lies in its simplicity. Except for the sun, earth, and clouds, no moving parts are required for passive heating and cooling. passive-solar design elements include south-facing windows to let in the sun during the winter; thermal mass, interior, to store the solar energy once it’s inside; and appropriate roof overhangs and trellises to keep out the sun in summer.
This house has a long center wall flanked by two opposing shed roofs. The longer east-west axis provides ample opportunity for south-facing windows. pop-up roofs lift to the southern sky in three locations. These roofs allow natural light to penetrate into the house, making it feel bigger, orienting interior spaces to the natural world, blurring the line between indoors and out, and providing a substantial aperture for solar-heat gain.
To shade the windows under the pop-up roofs appropriately, the overhang increases in size as the window increases in height, adding a dramatic effect to the roof. Determining the right size for a shading device is done with a scaled section drawing. modeling the windows and overhangs on a computer can provide complete visual information about the quantity of sunlight entering the house for any day of the year. in addition to roof overhangs over all south-facing windows, two covered porches keep the house cool in summer by blocking the low morning sun from the east-facing windows of the kitchen and the low afternoon sun from the west-facing windows of the master bedroom.
In winter, heating can still be difficult without the right amount of thermal mass inside the house. The tile-covered concrete slab and stonework around the woodstove and archway absorb the excess heat of the day, then release it slowly at night. This thermal mass also provides significant passive cooling in the summer. Slab-on-grade construction has other benefits. Keeping living spaces close to the ground means that there are no steps or pressure-treated decks between inside and out; moreover, there is no need for crawlspaces or basements, two problematic spaces in terms of indoor-air quality. A concrete slab is also ideal for radiant-floor heating.