On the Path to Zero Energy Homes Page: 4 of 6
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FSEC had shown that heat transfer to the duct system can rob
the air conditioner of as much as one-third of its cooling capacity
during the hottest hours. Oversizing the ducts allows high air flow
and low friction loss (previously shown to provide as much as a
12% improvement in cooling efficiency at essentially no extra cost).
High-efficiency appliances and lighting further minimize the Zero
Energy home's electrical load. These appliances and lighting also
release less heat into the home while operating, which decreases
the cooling load that must be met by the air-conditioning system.
The smaller appliance, lighting, and air-conditioning loads result in
less FV capacity required to meet the home's total electrical load.
A programmable thermostat-set so that the indoor tempera-
ture is allowed to increase overnight and while the house is unoc-
cupied-decreases the number of hours per day the air condition-
er operates. Running the air conditioner less reduces the
total electricity consumption and lowers utility costs.
- L ff4"y
-- - '
IZ-0O Wana (4t
The Energy Savings Picture (for Cooling): The estimated percentage of energy
savings attributed to each measure used in the Zero Energy home.
The solar water heating system supplies most of the
" t hot water for occupant needs. Its energy output is
equivalent to that of a 2-kW FV system.
All told, the combination of
efficiency features reduces
the cooling loads so that a
downsized air conditioner
suffices-and, here too,
-3 FSEC chose a high-efficiency
appliance. The small size of
this system (half that of the
control home) is highly unusual for
such a large home (2,425 square feet)
in Lakeland, Florida, but it's performing to expec-
tations. In addition, the unit's cooling coil
air flow was field-verified at the
Zero Energy house, which involves
using a flow hood to adjust the
fan speed of the variable-speed air
handler. Installers who neglect
this crucial step commonly cost
the system a 10% drop in actual
For illustration purposes, some features of the Zero Energy home have been relocated (versus actual).
Zero Energy home Features
" 2-kW solar water heater
" 4-kW utility-interactive PV system
" White-tile roof with 3-foot overhangs
" K-30 attic insulation
* K-10 exterior insulation over
concrete block system
" Advanced solar control double-glazed windows
" Oversized, interior-mounted ducts
" High-efficiency refrigerator
" High-efficiency compact fluorescent lighting
" Programmable thermostat
* Downsized SEEK 15.0, variable-speed, 2-ton
air conditioner with field-verified cooling-coil
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Merrigan, T. On the Path to Zero Energy Homes, book, March 30, 2001; Golden, Colorado. (digital.library.unt.edu/ark:/67531/metadc719975/m1/4/: accessed December 13, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.