Throw your weight around
A passive solar home needs thermal mass to function properly. This regulates temperatures, keeping the house cool in the summer and warm in the winter. It can be a creative centerpiece or an obscure element that's hardly distinguishable from a standard
stick frame wall.
Limited only by your imagination, create thermal mass in a slab, tile, concrete, brick, stone, water or an earthen wall. But make sure it's thick enough. A standard quarter-inch-thick ceramic tile isn't enough material.
Spherical Design Engineers
recommends the mass be at least three or four inches thick or it warms too fast and doesn't hold the heat: "
Building a thermal mass structure opens interesting design opportunities. Using concrete floors that act as foundation, floor and mass that take a long time to heat up during the day and vents off the heat when windows are open at night. Building hallways with lots of windows - hallways that double as libraries, alcoves or reading nooks, with rammed earth, plaster on straw bale or concrete walls that act as decorative features" and heat collectors. A waterfall fountain to divide two sections of a sunroom. It provides evaporative cooling while it flows during the summer, then sits still to create a pool of motionless water mass to collect winter heat.
Thermal mass doesn't have to be obvious to be effective. Thermal mass can be hidden inside partition walls using concrete masonry blocks. The walls are a bit thicker than your average stick construction, but it's doubtful anyone would ever notice. In residential areas, this is an easy way to build thermal mass that works both
aesthetically and space-wise.
Sweat the details, no matter where you're building
Passive solar heating and cooling ideas don't change too much from hot to cold climates. It functions great everywhere, especially if you learn how to maximize the benefits of your homes climate and keep common sense construction rules in mind.
Spherical Design Engineers
recommends building an airtight house where no more than one-third
of a house's air exchanges with the outside each hour. Avoid fiberglass
batts for insulation
, because they don't stop enough air movement.
Instead, use blown fiberglass, cellulose or rigid foam. Use R-50 insulation
in the attic and R-19 or higher in the walls. And don't forget to
insulate your basement, sub-floor or slab to at least R-10. Make sure
duct work is tight and pick windows with the Energy Star logo preferably
with a U-value of .35 or less.
To keep cool, it's important to use your prevailing winds. Maximize cross winds by putting high and low windows on opposing sides to move air through the house. If summer temperatures drop at night, open windows to let the air in and dramatically cool off the thermal mass. And if it's exceptionally hot, like Las Vegas, the best design lets in as little air as possible - ideally with thick adobe and straw bale walls and something like a sod roof to reflect and evaporate heat.
Staying warm has similar principles. Thicker walls help augment the mass, while openings need to be limited everywhere except the south side in freezing climates. Construction needs to be extra tight.
And if it's still not warm or cool enough, many extra efficient technologies can easily augment a passive system using far less energy than traditional air conditioning or heating. Radiant heat floors use low temperature heating systems. A ceiling fan effectively stirs heat and moves air year round. Swamp coolers use about 75 percent less energy than air conditioning. (Note: A swamp cooler, or evaporative cooler, using a fan to push hot outside air first past
water wetted pads, cooling the air, and then into the house.)
"When people think solar, they think PV panels or hot water. When it comes to passive, they don't have a lot to look at. People just don't see it enough. It's not as tangible as solar panels on your roof, even though it's incredibly effective. Ultimately, passive solar will be cast into the mainstream of new construction by other forces: high energy prices.