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Project
History
The builder and original owner was William Gallagher. Starting
in 1992, he spent 6 or 7 years of his life in researching,
planning and building the home. He purchased the site in
1994 and with the design assistance of college friend and
architect, W.S. Jones of Manhattan Beach, CA., broke ground
in 1995. The principle investigator was asked to consult
on the radiant system and agreed to do so if monitored data
would be made available for research purposes. The house
was completed in late 1998 and sold to the current owner,
Patsy Miller, in early 1999. In that year, ASHRAE awarded
a research grant to monitor the house's performance. Continuous
reliable performance data began in August of 2000.
The
Site
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The project location is in Carefree, Arizona at 9441
East Romping Rd. |
The
site is located in what is known as the high desert, 30
miles northeast of downtown Phoenix. Because of its 2500
foot elevation, its temperature is approximately 5 degrees
F cooler than that recorded at Phoenix's Sky Harbor airport
(elevation 1100 feet). It tends to receive more rainfall
and the air is clearer than that of Phoenix.
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Bill Gallagher at site before start of construction,
March 1995. |
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North side
showing main entry |
House
Envelope:
The house is a 2500 SF single story adobe house containing three
bedrooms and two baths. The exterior adobe walls are insulated
on the outside with 2 inches of sprayed on foam. The entire occupied
floor area has hydronic tubes buried in the concrete slab. Approximately
60% of the ceiling contains hydronic capillary tubes.
The foundation stem wall is insulated on the inside (between the
wall and the slab) with 2 inch (5 cm) foamboard. The 5-inch (13
cm) slab is poured over gravel with no insulation below is an
excellent thermal storage device. On top of that is another two
inches (5 cm) of mass - an inch (2.5 cm) of grout then topped
with an inch of flagstone. The slab contains 10 mm (3/8")
diameter rubber tubing at a spacing of 23 cm (9").
The exterior walls are constructed of 36 cm (14 inch) adobe. The
exterior adobe walls, enclosed in insulation, represent considerable
thermal storage. Their exterior length is approximately 300 feet
(91 m), their height averages 8 feet (2.4 m). There is 95 lineal
feet (11.4 m) of interior adobe wall. Still to be answered by
simulation work is, how much of the mass will be usable for thermal
storage.
Floor plan
showing sensor locations |
Roof/ceiling
assembly |
Reflected
ceiling plan with tube locations |
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click on images for clear images >
For a predominately cooling climate, theory predicts that a cool
ceiling would provide better room convection patterns in the summer
season, while radiant floors would provide the patterns best for
the heating season. Fifty-two percent of the ceiling area of the
home is a radiant panel, sized for the cooling load of approximately
60 W/m2 (20 Btu/ft2) . The manufacturer states that the capillary
mats can provide cooling at 80 W/m2 (27 Btu/ft2). To prevent condensation
problems, the construction details of the roof/ceiling assembly,
shown above, were specially designed. Below the wood roof joists
is a continuous vapor barrier to prevent moisture from reaching
a surface whose temperature is below the dew point; then 1 inch
of Styrofoam insulation board; a half inch of gypsum board; and
3/8 inch (1 cm) of sand plaster. At a depth of 6 mm (0.25 in)
in from the surface of the plaster is a capillary tube mat. The
tubes are 2mm diameter plastic spaced at 12 mm (0.5 in). They
are connected by a 16 mm (0.63 in) supply header and another 16
mm return header. Shown above is a reflected floor plan with the
ceiling panel layout. 119 sq. (1300 sq. ft.) meters of panels
were installed over a floor plan of 229 sq. meters (2500 sq. ft.).
Figure 4 shows capillary tube ceiling mats fastened to dry wall.
Capillary tube ceiling mats are one meter in width and of varying
lengths -- from one meter to 4.5 meters in length. Therefore,
a single capillary tube length (from supply header to return header)
varies from one meter to 9 meters. Naturally, the temperature
drop through a longer tube is greater. So, for the cooling mode,
the longer the tube, the higher the average temperature. Since
a room can contain mats of several lengths, varying temperatures
will occur across a room's ceiling, although only one ceiling
sensor was installed in each zone.
There are four 3' x 3' (91 cm x 91 cm) operable skylights on the
north slope of the roof. Mini-blinds were installed in April 2002.
This has improved the thermal performance of the house. At certain
times of the year prior to the installation of the mini-blinds,
direct sun would come through the skylight and strike the center
zone thermostat, causing a spike in the air temperature and operative
temperature. The skylights provided benefits in the swing seasons
when they would be open lights for venting and night ventilation
to extend the passive comfort performance of the house.
Windows are double pane with the four-foot overhang around the
house, and shaded for most hours of the year.
Environmental Control System:
The environmental control system is made up of both passive and
active components.
Passive components include the thermal mass of the floor and the
outside insulated walls, the operable skylights, the wide overhangs,
and low e coated double pane operable windows.
The active environmental control system consists of the radiant
floor and ceiling panels supplied by warm and chilled water from
a ground source heat pump cooled by an evaporative fluid cooler
and heated by flow to vertical wells, the central and zone control
system, and separate convective system -- ventilation and dehumidification
package units for indoor air quality. Below is a schematic (Figure
5) of the entire active environmental control system - a hybrid
(radiant/convective) system. The radiant system provides both
sensible heating and cooling.
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The nominal 3-ton unit produces chilled and hot water for the
hydronic radiant system. It receives and rejects heat from/to
the ground with a well field of 10 wells averaging 60 feet in
depth. It also provides domestic hot water. Each zone has a manifold
for both the floor and the ceiling. A separate solenoid valve
controls the flow to each. The ground loop is made of 1-inch plastic
tubing. It is divided into three sections in parallel, two of
the sections have three wells in series and one section with four
wells in series. Operational performance during the summer of
2000 showed that the ground loop heat rejection capacity was too
low. This resulted in very high condensing temperatures and lower
than expected cooling capacity to the house. So, on May 22, 2001,
an evaporative closed loop fluid cooler was installed in series
with the ground loop.
There is an energy recovery ventilator for both the west and the
center zones, but not for the east zone. The incoming fresh air
then passes through the dehumidifiers before being supplied to
the occupied spaces. The package dehumidifiers are also in the
west and center zones.
Heating and cooling capacity:
The capacity of the panel systems depends on the heat exchange
between the panel surface and the space (convective and radiant
heat exchange coefficients), the heat conduction between the panel
surface and the tubes (panel surface material, panel thickness
from tubes to surface, panel material, spacing of the tubes) and
the heat transport by water (flow rate, temperature difference
between supply and return).
To prevent any cracking of the plaster, the ceiling was not intended
to be heated, however, tepid water at 85°F (29°C) is pumped
through the ceiling during the early morning hours if its surface
temperature is below 70°F (21°C). With the bare floor,
considering a 3" overpour with tubes at 9" on center
the estimated capacity is 27 Btu/h*ft2 (79 W/m2) (Kilkis 1995b).
Ceiling was designed for a capacity of 20 Btu/h*ft2 (60 W/m2)
(Kilkis 1995a). The maximum cooling capacity (Olesen 1977) of
a floor, based on maximum room air temperature 78.8°F(26°C)
and minimum floor temperature 68°F(20°C) is 42 W/m2.
Data Collection:
There are two data collection systems. One is a function of the
control system, Johnson Controls (JCI), and collects system operational
data and some climate data while a second separate (National Instruments-
NI) system collects envelope performance and solar data. The JCI
system stores 30 variables every fifteen minutes and two electrical
meter pulses every minute, while the NI system stores thermocouple
and solar averages every 15 minutes.
Installed sensors:
Figure below shows the house floor plan with the location of installed
sensors. These include sensors for surface temperatures, air temperatures,
and relative humidity whose readings are collected by the Johnson
Controls system. Also shown on the plan are the locations of thermocouples
that provide data to the National Instruments data collection
system. Figure 5 shows the system schematic with the location
of sensors that indicate the performance of the ground source
heat pump and the hydronic distribution system. An electrical
meter with a pulse output is installed on the heat pump (includes
the ground pump), while a second meter monitors the total house's
consumption.
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Weather Data:
There is a separate weather file that was developed for simulation
work. Weather data was compiled from the data collected at the
site project (elevation 2500 ft) and also the Phoenix TMY2 file.
