Anyone who’s familiar with solar-heated houses knows
that there are any number of ways to harness the sun’s
energy, from the simplest “passive” approach (the
“little guy’s” method) all the way up to the expensive,
highly technical, “active” systems that big business tends
to promote.
Recently, one of MOTHER EARTH NEWS’ staffers and a photographer
went to Landenberg, Pennsylvania to look at one of the
“simple” systems and to talk to its designer–produce salesman-turned-builder Jim Kries–who is in
the process of constructing a small community of passive solar houses; he calls them, very appropriately, “Sunburst” homes.
Mind you, though, these houses don’t utilize what you
might call your “average” solar collector. Instead, Jim has
opted to incorporate a “Trombe wall” (named after its
inventor, French physicist Felix Trombe), which not only
heats the house without any moving parts or expensive
equipment, but makes the dwelling as attractive (at
least!) as any custom-built conventional home. In fact, the
owners of the house–Vincent and Kathy
Polidoro–decided to buy it when they saw the blueprints before construction of the home had even begun. And,
after talking to the Polidoros, we’re convinced that they
haven’t been disappointed at all!
It’s no secret that solar-heated dwellings have come into
their own in the past decade or so, thanks largely to
the efforts of many “unconventional” yet dedicated
designers. Folks like David Wright, William Shurcliff, Steve Baer, Bruce Anderson, and a host of others saw a
definite need to “make hay while the sun shines” rather
than just sit around and complain about the rising costs of
fossil fuels.
And there’s no doubt that these solar homes really work despite what the skeptics say about cloudy days,
winter storms, and other “no-sun” situations. But with a
few exceptions, most effective solar homes aren’t as
attractive as their designers or the public would like them
to be. Let’s face it, there’s not too much you can do to
improve the looks of a solar collector without lowering its
efficiency. Until now that is, because the Jim
Kries-designed “Sunburst” solar house is a real beauty!
You see, instead of trying to “hide” the collector in the
back yard, Jim decided to use it as the entire
south wall of the ground floor. To do this, he built a
14-inch-thick, 225-square-foot “Trombe wall” which is
painted black on its outer surface (to absorb and hold the
sun’s heat) and is finished in white stucco on the inside
(to assure an attractive, light, “airy” look in the house’s
dining and living room areas).
Of course, this “collector wall” isn’t directly exposed to
the weather. Instead, the entire surface is faced with
another 225 feet (or so) of 5/8-inch-thick insulated glass,
which is mounted from floor to ceiling about six inches in
front of the actual collector. The double wall creates a
passageway for the heated air to follow. And, as Kries is
quick to point out, that insulated glass–although it is
expensive–is no more so than common replacement panes for
sliding doors because that’s exactly what it is! In
other words, instead of using fancy solar hardware where
it’s not needed, Jim “made do” with standard building
materials to reduce costs and to insure that
replacements would be available in the event of accidental
damage.
So what we have, then, is a low-cost, simple way of
collecting and storing heat … which is great in the
winter. But what about the summer? Well, Jim has that one
figured out, too. The
south-facing upstairs wall (the one which is above
the Trombe wall) is cantilevered three and a half feet
beyond the glass “wall” below it. This overhang effectively
protects that expanse of glass from the rays of the high
summer sun; if the sun can’t get to the glass or
the black wall behind it, no heat is produced. Also, most
of the rays that do find their way to the collector surface
just “bounce off”, because of the oblique angle at which
they strike the glass.
To insure that the house is completely free of
unwanted hot air in the summer, Kries installed a large
attic fan in the dwelling’s second-story roof. Though he
doesn’t foresee a need for this addition, Jim explains that
the fan serves as a positive “warm air exhaust route”,
which might be needed in the event of unusually
hot or humid summer weather.
Supplemental Heat … Just in Case
The Trombe wall–despite its size and mass–still can only
provide about 60 to 75% of the house’s total winter heating
needs (an impressive percentage, considering the low-cost
simplicity of the system). Therefore, Jim added two
auxiliary heat sources,which-he hopes won’t ever see much
use.
The main “backup system” is a 98,000 Btu/hr.,
thermostat-activated, oil-burning hot water furnace
which, because it’s a two-zone design (“two-zone” means that
the temperatures of two different areas can be controlled
separately), only supplies heat where it’s actually needed.
Although the furnace is capable of providing all of the
heat that would ever be necessary, Kries hopes that it will
only be used on the coldest of days. The thermostats are
set at 55*F, and thus far–says the builder–the furnace has
not had to come on.
In addition to this “conventional” source of heat, Jim also
makes use of an attractive Morso 1125 wood burning stove
… a unit that’s not only favored for its high Btu output,
but because it can also be converted into a fairly efficient
“open fireplace” by removing the doors. And, since the
Sunburst house is located on two wooded acres, fuel supply
should be no problem.
Insulation Makes the Difference
Jim was determined to make his design as energy efficient
as possible, and that meant using insulation to its fullest
potential. To accomplish this, Kries framed the entire
structure with 2 X 6’s on 24-inch centers (instead of the
usual 2 X 4’s). This gives the house a rocksolid
framework and allow a greater-than-usual amount of
insulation to be used. Jim took advantage of this extra
space, too. He installed six-inch fiberglass batting
(over one-inch styrofoam sheeting) in the walls, and nine
inches of batting in the ceiling.
In addition to insulating the walls and ceiling to the
limits (they have R-values of 24 and 30 respectively),
Kries also paid special attention to the foundation of the
house (the 16-inch-thick “solar slab”) by first laying down
a full inch of tongue-and-groove styrofoam. This material
was covered with six inches of gravel, which in turn was
topped with six more inches of concrete. Finally the
foundation was finished off with 3 inches of brick veneer,
which serves as the floor of the living room. Not only does
this “layering” prevent cold from seeping in through the
foundation, but it also stores warmth within the mass of
the floor. . . which works in concert with the Trombe wall
to hold collected heat and release it slowly. (The Trombe
wall is mounted directly on the insulated “solar slab”
foundation of the house … which also supports the masonry
chimney in the center of the building. In this manner, both
the heat collected through the Trombe wall and
that absorbed by the chimney via the fireplace are held
inside the entire structure for up to 16 hours).
But the high insulation factor isn’t the only thing that
keeps heat within the house. Jim has made clever use of
“airlock” double-door entryways (a fancy way of describing
old-fashioned vestibules). He also relies on several
south-facing windows to admit heat (and light) into various
rooms in the house, including the living/dining area
behind the otherwise solid Trombe wall.
