to a set of swales or into a small terrace pool. During warmer months,
pool water is recirculated by a solar-powered pump through a biological
filtration area. One of my favorite aspects of this roof design is the fact
that I have no gutters to worry about. My neighbors use electricity to heat
theirs to prevent ice clogs.
Neighbors also use humidifier systems. I have a greenhouse on the
south side of the master bedroom, and it contains an “endless river”
pool. When the air is dry, a humidistat turns on a simple fan to bring
humid air from the greenhouse into the main house. This gives me 30
to 50 percent more humidity than I would otherwise have indoors. The
unheated greenhouse is three to four USDA Plant Zones warmer than the
average outside winter zone. I can easily grow citrus and lavender, as well
as a variety of plants commonly found in the San Francisco Bay area. In
spite of the harsh climate and difficult site, the house has become a quiet
retreat, an inspirational workplace and great place to watch the weather
and local wildlife.
energy Systems Provide Solar Cat-approved Warmth
The house uses a variety of active and passive solar systems, and systems that aid ventilation, daylighting, heat retention and humidification.
Because the house is located in high desert with an average of 6,500 heating degree-days per year (F), it needed solar heating as well as ventilation
and cooling. The mountains loom to the west, blocking late-afternoon
sun; thus the solar orientation of the house is a bit east of true south (I lose
the sun at 2: 30 p.m. at winter solstice). The standing-seam metal roof of
the main house tilts 13 degrees from horizontal, making it a reasonable
platform for part of the PV array. The rest of the array is mounted on a
trellis over the terrace.
The radiant heat system is powered by seven solar collectors, each 4
feet by 10 feet (1.2 meters by 3 meters). These collectors heat a glycol/
water mixture for domestic hot water (DHW) and space heating. After
passing through a heat exchanger for DHW, the fluid is distributed into
loops of tubing buried in sand beds under the concrete floor slab. Together,
the sand and concrete serve as thermal mass to store heat and release it
slowly and evenly into the living space. As the weather grows warmer, the
fluid can be diverted into a heat exchanger used to heat the pool. This
type of sand bed solar thermal system was explained in Bob Ramlow’s
article, “Warm, Radiant Comfort in the Sand” (SOLAR TODAY, November/
December 2007). The cost was $12,000 (not including installation costs),
compared to the $20,000 or so I would have paid for a nonsolar radiant
In addition to the concrete slabs, the walls provide thermal mass.
They’re built of straw bales above an insulated concrete form (ICF) foundation, with 2 to 3 inches of soil cement finish on the exterior and on the