Page 20 - Green Builder September-October 2018 Issue
P. 20
Annual Building Science Report 2019 EFFICIENCY MATTERS
request, a third system was installed consisting of
a minimally ducted mini-split heat pump with fan
coils to provide back-up heating and cooling to the
bedrooms. This redundancy may seem excessive
for a passive house, but according to builder Je
Adams, “the system has been designed for a climate
that could be dramatically dierent in years
or more.”
The solar thermal system is also the primary
source for the home’s potable hot water. The air-
to-water heat pump and an -gallon heat pump
water heater provide backup domestic hot water.
The hot water distribution system was designed
COURTESY OF ALLIANCE GREEN BUILDERS any bath or kitchen xture.
to cut water loss to cup before hot water reaches
The hilltop home is self-sufficient for water.
Five ,-gallon tanks collect rainwater from
the roof to supply percent of the family’s
collect stormwater from the site, and one additional
One with the sun. Casa Aguila performs far better than net zero, thanks to a super-efficient indoor water use. Four more ,-gallon tanks
, gallon tank collects graywater (from the
building shell, a wind turbine, three sun-tracking solar photovoltaic arrays and solar thermal shower, baths, sinks and washing machine). This
water heating. stormwater and graywater is ltered and used for
threat, Alliance installed triple-glazed, tempered glass windows with irrigation and re suppression. A separate system collects blackwater
an outer pane of impact-resistant laminated glass. The R- insulated from toilets and kitchen sinks in a septic tank; from there, it is
windows also provide year-round energy eciency with coatings to aerated and ltered, and the clean water is pumped into another
reduce heat transfer. ,-gallon holding tank for drip irrigation.
The roof consists of -by- rafters topped with ⁄-inch OSB coated The homeowners requested an electric production system that
that is coated with the liquid-applied waterproong membrane that can allow the home to eventually go o grid. Three large dual-axis
also covers the wall sheathing to form a continuous air and water solar trackers were installed on a leveled area south of and below the
barrier. This is topped with -inch-thick structural insulated panels home. Each tracker holds square feet of photovoltaic panels, for a
(SIPs) that have a polyurethane core with a higher melting point than total capacity of kW. The panels can rotate in multiple directions;
most foams. The SIPs are covered with a roong underlayment and
a standing-seam gray metal roof with a solar reective index of
to help resist solar heat gain. Netting is attached to the underside of
the roof rafters, and the space is lled with blown cellulose. Below
that is a -inch gap and then -by- ceiling rafters that are covered
with the phase-change material and drywall. The gap provides more
space for insulation above the recessed can lights.
The home’s slab-on-grade foundation is wrapped in inch of
expanded polystyrene (EPS) insulating foam. Embedded in the
concrete is plastic piping for the home’s radiant heating and cooling
system.
FORWARDTHINKING TEMPERATURE CONTROL
The home actually has several heating and cooling systems. Most of
the hot water for the radiant oor heat is provided by nine -by- COURTESY OF ALLIANCE GREEN BUILDERS
( square feet) solar thermal collectors mounted on the roof. An
air-to-water heat pump provides backup water heating and water
cooling. Additional water cooling, should it be needed for extremely
high summer temperatures, is available via a ducted fan coil system Aqua Aguila. Solar thermal panels provide hot water for the pool, spa,
(with cold water from the air-to-water heat pump). Per the owners’ domestic hot water and radiant floor heat.
18 GREEN BUILDER September/October 2018 www.greenbuildermedia.com
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