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The high-tech house offers relief irom summer heat not only by
means of power-hungry air conditioners, but also through shade
trees placed along the south side of the building. Heat in winter
can come from a gas-fired furnace and also from warm air radiated from a solar mass beneath the floor. Smarter design and new
technolog>' are keeping the options open.
Unconventional ways of improving heating have received
widespread attention since the 1973 oil embargo. The methods
hinge largely on harnessing the power of the sun. So-called
passive solar systems stress proper orientation of the house and
using the sun to heat spaces and materials. Active solar systems
rely on moving parts such as heat exchangers and computercontrolled window curtains.
"Passive solar" really means smart design. For a house in the
Northeast, for example, it makes good solar sense to design small
windows on the north facade, to shut out cold winds, and large
windows on the sunny south side, to absorb the warm rays. Even
in the active solar house, these straightforward measures help
heal the house without pumps, motors, ducts, and burners.
Increasingly, so-called solar mass is being used to enhance the
natural space heating that occurs when the sun streams in
through windows. Building a sun room on the south side will
bring warmed air into the rest of the house, but a low stone wall
at the rear of the sun room, rather than a standard wall, will absorb the sun's heat and reradiate it into the house long after the
sun has set.
Other simple design measures also qualify as passive improvements in heating and cooling. A simple front door can be enhanced with a small foyer that has an inner and outer door.
Someone arriving opens the outer door, enters the foyer, and
closes the door. He may hang his coat and leave his muddy shoes
there, then open the inner door and enter the house. In the summer this arrangement prevents gaping losses of cooled air; in
w inter it locks out inrushes of cold air.
Similarly, a walkway between an unattached garage and a
house can cut heating losses through an uninsulated garage. walkway with doors at both ends keeps the garage "attached,"
which is convenient, but eliminates heat loss and also locks out
harmful car exhaust and other fumes.
Active solar systems offer further benefits, but usually at
higher cost because of the equipment involved. An important
consideration, though, is that they give options to home owners
whose homes are already built but are not designed for passive
solar. Active solar heating was first used widely to heat water;
solar collectors on the rooftop can be seen in many communities
today. But more elaborate arrangements are now being tried.
Robert Starr's home in Lyndonville, Vt., for example, relies on
solar collectors for all its hot water and space heating. During
sunny weather, an electric pump pushes a combination waterantifreeze solution up through seven rooftop collectors. The
returning warm solution feeds a heat exchanger, which preheats
the hot tap water, and two piping circuits. Each circuit consists of
four serpentine loops of -/4-inch polyethylene piping, each 200
feet long. These extend below the house, circulating through a
6-in. concrete slab on which the house rests. A separate circuit of
four similar pipes travels through 2 ft of earth packed below the
concrete.
The solution in the two loops gives up its heat to the concrete
slab and earth. The cooled liquid then rejoins that coming from
the heat exchanger and is pumped back up to the collectors.
There are no pumps to draw heat out of the concrete and earth
mass—the heat is simply radiated by the concrete, which in turn
is kept warm by the warmed earth beneath it. Manual valves control each loop—it did not pay to install electric ones, because of
their cost and the power they would consume. Hence the amount
of heat is controlled by only one powered component—the
pump.
Typically the temperature of the concrete slab is 65° to
70°F—10 to 20° below that of most thermal masses directly exposed to sunlight, but warm enough to keep the indoor air comfortable at night. Heating during the day is gained directly
through large windows. Although most active collectors operate
at 120° to 180°, those on Starr's house stay below 90°—thus less
heat is lost because of the smaller difference in temperature be smart design and a few manual maneuvers can greatly aid the
natural heating and cooling capability of a house, as in the La
Honda, Calif, home of David Brodhead and Joy Asdoorian. In
winter excess heat from tiie ground floor is blown into the entry
hall, where it is cycled through the upstairs and ultimately recycled through a central stone (thermal mass) wall via a duct runtween Starr's collectors and the outside air. Keeping temperatures
low throughout the system raises its heat-conversion efficiency to
between 60 and 70 percent.The concrete slab heats the indoor air directly because it forms
the house's main fioor. For purposes of decor, Starr covered it
with 5/16-in.-thick wood tiles, bedded in mastic, which do little
to diminish the radiated heat. Starr's 1400-square-foot house cost
$52 000, including the land. He used only 18 gallons of home
heating fuel from October 1982 through April 1983 for auxihary
heat, according to a study of the house conducted by the U.S.
Department of Energy's Solar Electric Research Institute (SERI)
in Golden, Colo. Without the solar features, some 550 gal of oil
would have been needed, SERI concluded. At the then
$1.19-per-gallon average U.S. price for home heating oil, the additional fuel would have cost $633