TechPractices are outstanding housing projects throughout the U.S. where innovative technologies are implemented. Builders and remodelers can use these examples as models for projects of their own.
|Keith Swilley House Snapshot
||Panama City, FL
||Koehnemann Construction, Inc.
||Owner-occupied single family custom home
||Geothermal heat pump, horizontal loop with desuperheater, wet-blown
cellulose insulation, duct sealing, duct blaster, fluorescent
lighting, induction cooktop
This single-family Florida house uses a horizontal loop geothermal
heat pump system and an array of energy-saving strategies.
Built for less than $50 per square foot (not including land)
this home is below median home prices for the region. The high-quality,
energy-saving design makes it comfortable to live in and affordable
Homeowner Keith Swilley wanted his new house to be very energy
efficient. Because he might have to move in a few years, every
design and technology was scrutinized for maximum energy savings
and short-term return on investment. But despite the short payback
requirement, he installed a WaterFurnace geothermal heat pump
(EER 16.0, COP 3.6), known for being high performing and somewhat
costly. Swilley did this because he knew that between the energy
savings and the increased resale value of the house, he could
recoup the additional expense of the geothermal system. Augmenting
the heat pump is a desuperheater that provides "free" hot water as long as the heat pump is in operation. Other efficient
solutions include highly insulated walls and ceilings; air-tight
construction to reduce infiltration; a sealed HVAC duct system
minimizing distribution loss; and energy-efficient lighting and
appliances. These products and systems increase front-end costs
but greatly improve whole house energy performance.
Located in the western Florida panhandle, Panama City's residential
electric rates are $.06/KWH. Because rates are low, even a big
percentage reduction in energy use doesn't equate to very large
dollar savings monthly. Despite the longer payback and higher
initial cost (the Water Furnace system cost about $3,000 more
than an air based heat pump) geothermal is used because of its
superior heating and cooling performance, and for its capability
to dehumidify. This owner sub-meters heat pump and hot water use
to monitor actual equipment performance. The average cooling and
hot water use in this house is 48% of total household energy use
on an annualized basis. That compares to 70% or more for average
residential energy use.
Geothermal heat pumps have been recognized by the US Department
of Energy as one of the most efficient solutions for residential
heating and cooling. Like refrigerators, heat pumps remove heat
from where it is not desired (inside a freezer), to a pump it
where it can be expelled (the back of the refrigerator.) In the
geothermal variety, a fluid-filled polyethelene pipe, buried in
the earth, augments the heat exchange process. During operation
in the heating season, fluid in the loop transfers heat from the
ground, via the heat pump, to the house. In cooling, the heat
from the house loops through the ground, is cooled, and returns
to the house ready to cool and start the cycle again.
To keep his lighting loads low, the homeowner installed fluorescent
pin lamp (PL) lighting fixtures for all general illumination.
In the utility rooms and garage he upgraded standard fluorescents
to T-8s with electronic ballasts that are said to be 40% more
efficient. In the kitchen, an Energy Star refrigerator, a convection
oven that cooks food 33% faster and an induction cooktop that
uses half the amount of electric energy as a conventional cooktop,
help assure energy efficiency.
Trenches are dug for the closed loop geothermal heat pump system.
The one-acre lot provided enough land with sufficiently moist
soil for a horizontal installation with three 100'-long trenches
each 5 feet deep. Each 100-foot trench has 600 feet of ¾-inch coiled
polyethelene pipe laid in successive loops, called a mat loop,
like coils of a slinky. This maximizes ground contact with the
least amount of digging. The homeowner saved money by using his
house excavator to install these loops as the site was being readied
for the foundation. (If lots are small or soil conditions especially
rocky, closed loop "wells" can be drilled vertically
into the ground.) Extremely durable, polyethelene pipe is used
by the natural gas industry for its in-ground gas supply lines.
Once three loops are joined to the 1¼-inch polyethelene
feeder pipe and brought to the house, construction can begin.
The 40-foot by 50 foot house sits on a slab-on-grade, insulated at the
perimeter edge with ¾-inch rigid foam. (Under-slab insulation
is not effective because ground temperature in Florida is close
to 70 degrees Fahrenheit year round.) This one-story building
is framed with 2 x 4 walls that are sealed at the base with Dow
sole plate sealer and insulated with R-13 wet blown cellulose
which is said to reduce air infiltration when compared to walls
of fiberglass batt. The studs are sheathed with ½"
plywood, insulated with ¾-inch rigid foam, and covered
with conventional stucco. This brings the exterior wall insulation
value to R-19. Loose filled cellulose is blown into the ceiling
joists making an R-38 ceiling. The roof is framed with engineered
trusses, sheathed with ½-inch plywood, and covered with
The double-glazed aluminum windows by Mayfair have an infiltration
rate of .23 per lineal foot of sash. The Therma-Tru exterior doors
are R-8. Doors and windows are sealed in their framed openings
with expanded foam sealant to reduce infiltration. A blower-door test of the house revealed an average of 0.25 air changes per
hour (ACH), which is less than half the infiltration rate of a
typical new house in this region.
The fan coil "furnace" of the heat pump is located
in a closet off the garage, while the feeder ground loops are
connected through the slab. Metal ducts from the furnace run through
the attic space and are oversized to reduce noise. Additional
noise reduction is achieved with expensive curved fin diffusers
spaced farther apart. Because the ducts run through unconditioned
space, trunk lines are insulated with an R-6 wrap and distribution
branch lines are R-6 flexible duct. All joints are sealed with
mastic to reduce air leakage, and the entire system is tested
using a duct
blaster before occupancy. A system is considered in compliance
if duct losses are less than 3% of floor area. Actual tests revealed
only 1.5% duct leakage.
Beside its touted performance and operating superiority, why
chose an expensive, geothermal heat pump system, especially if
you don't plan to stay in the house as long as the payback period?
Other than improved comfort and lower bills, the reason may be
marketing. This owner has built and sold three houses. Each included
more energy-efficient features than the previous house, and each
sold quickly because the buyers appreciated such features. In
a cooling-dominated residential market, geothermal heat pumps
may be a good way to distinguish otherwise comparable residential
properties. This conclusion is shared by builders Carl Franklin
Homes of Dallas, who consider geothermal heat pumps an essential
sales feature of their affordable housing developments in Texas.
Although this house does not tout affordability, it is priced
below the median. Competing with conventional construction while
offering long-term operating savings makes this home attractive
to conservation minded home buyers.
There were no significant code issues that arose during design
or construction. The builder points out that he exceeded all energy
codes by 20% to 50%. Although the buried ground loop pipe did
not require permits for installation, it did cause a flurry of
concern by building inspectors when it was first being installed
in the early 1980s.
Winning an Energy Value award from NAHB in 1997, and a Grand
Aurora award from the Southeast Builders Conference in 1996, puts
this house in an elite class. But Keith Swilley is not content
to rest on his laurels, and has come up with ways to improve on
his award winning work. On his "next house" list are
higher performance windows and a floor plan customized to his
family's lifestyle. The custom plan would allow him to bring the
furnace to the center of the plan, keeping the ducts
within the conditioned space and reducing duct runs. He plans
to keep building houses with geothermal heat pump systems. But
ventilation should also be considered in a house this tight. Relying
on window and door leakage may not be sufficient for good indoor
Do you have a specific question? Try the contacts listed below:
Gulf Power Company
Panama City, FL