By Arno de Villiers B.Arch.
7. Wide Roof Overhangs
Arno
Construction - Florida Certified Building Contractor CBC 1255481
1. Introduction
Many Florida residents are tired of the same old Mediterranean
architecture. It is time for something new and refreshing and at the same time
beautiful, contemporary, sustainable, high-tek and yes, affordable!
E-House #1 is my response to the increasing demand by singles, retired couples, empty nesters, etc for an affordable
home that can fit on an available small lot. It is a three bedroom, two bathroom house of only 1440
square feet.
2. E stands for Efficiency
Residential design keeps moving toward high-performance sustainable
building systems. To be sustainable, a
building must not only be efficient and durable but also economically
viable. New methods of enclosure have been
examined that provide high thermal performance and long-term durability. They reduce
material use, simplify systems and details, and potentially reduce overall
initial costs of construction.
3. Efficient Design
Educated design can make every square foot count, reducing wasted space by keeping hallways etc. to a minimum. The effective use of construction dollars calls for efficiently designed spaces and scientifically considered building envelopes that provide both security and cool economical thermal environments.
4. Energy Efficiency
Living in Florida conjures up swaying palms, swimming pools
and fresh orange juice... and lots of air-conditioning. A summer spent in Florida’s heat and humidity
would be unbearable without it. Air-conditioning is an absolute necessity but
also a big energy drain accounting for about 35% of all electricity used in a
typical Florida house. Minimizing the loss of cool air to the exterior in
summer is the first order of business in an energy efficient Florida home.
5. Steel Frame and Rain-shield Insulated Walls
The use of a structural steel frame engineered to resist 150 mph hurricane
winds, plus an external panel rain-shield is preferred over the use of wood
studs, plywood and OSB. The latter although considered renewable are subject to
destruction by termites, moisture and rot.
Note the E-House corrugated steel "rain-shield" outside walls
and the contrasting concrete block carport
6. High Insulation Levels
The U.S. Department of Energy has
developed a list of recommended insulation levels for different climate zones. Because
electric heat is relatively expensive, houses with electric resistance heat
need insulation to exceed the recommended levels. Most
insulation materials function by slowing the conductive flow
of heat. Materials with low thermal conductivity more effectively block heat
flow than materials with high thermal conductivity. The R-value of an
insulation material measures its resistance to heat flow.
For Collier county in Florida, the recommended
minimum R-values are: Roof = R-30, Walls = R-13, Floor = R-11. E-Houses’ unique roof
and wall assemblies are carefully designed to exceed these values. Polyisocyanurate or “polyiso” is no longer produced with HCFC's, and is now
the environmentally preferred rigid board insulation for above-grade
applications.
7. Wide Roof Overhangs
The traditional wide roof overhangs of old-style Florida homes
are seldom used these days. The assumption is that air-conditioning takes care
of cooling needs. But why make the air conditioner work harder and costing more
than it should? The E-House restores wide roof overhangs that aim to shade the
south and west windows from solar heat gain. The large gently sloping roof is
also perfect for collecting rain water for the garden or filtered for potable
use.
8. Reflective Metal Roof
Another feature is the reflective light colored standing
seam roof versus the popular grey, red and orange cement tiles or asphalt
shingles on the “Mediterranean” home. Even
if all homes have R-30 fiberglass roof insulation, one study shows that on a
day when the temperature in the attic of a standard Florida home rose to 138°F,
a similarly insulated attic under a reflective metal roof reached only 100°F.
(*1)
How about trading these gas guzzlers for new hybrids?
Note the battery closet for the PV system at the back of the carport.
9. Interior-Mounted Oversized Ducts
Oversized air-conditioning ducts, positioned within the
air-conditioned space as opposed to a hot attic are used in the E-House to advantage.
Tests have 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. Over-sizing 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).
10. Solar Control Window Film
Sun control window film can account for up to one-fifth of
the energy savings for cooling, rejecting up to 60% of the heat coming through
the glass. They can be carefully selected for both appearance and thermal
effectiveness. They transmit much of the light in the visible portion of the
solar spectrum, but limit transmission in the infrared and ultraviolet portions
which causes overheating and fading of interior materials.
11. Photo Voltaic Solar Panel System (PV)
Most installations in the U.S. are
grid-tied, meaning the house can draw power from either the utility grid or its PV array. When the PV cells aren't
producing enough power, the grid makes up the difference. When the array makes
more than the house consumes, the electricity flows into the grid.
Off-grid systems, which require a battery bank to store power, are more expensive and more complicated and can be considered as an optional extra.
Off-grid systems, which require a battery bank to store power, are more expensive and more complicated and can be considered as an optional extra.
Research has shown that a home in a climate such as Florida's
be engineered and built so efficiently that a relatively small Photo Voltaic
system would serve the majority of its cooling needs—and even some of its daytime
electrical needs and be as comfortable and appealing as the conventional model
built alongside it.
A comparative study of two Florida houses was made during
the very hot month of June. One house that was designed and built with these listed
features, consumed only 335 kilowatt-hours (kWh) of utility-grid power for all
its electrical needs. This compared to 1,839 kWh used by the unoccupied control
home for air-conditioning only! The monthly power cost in the first home was
only 18% of the control home’s power cost. (*1)
A PV system can be sized to provide power that would offset
as much of the household load as possible. Based on the predicted load for a peak
day, a 4-kW PV array (split into two sub-arrays) can be specified. One sub-array
can be located on the south-facing roof, which is generally the preferred
placement for a PV system. The other can be located facing west because this
orientation provides more PV power during the hot afternoons, when the utility experiences
its peak demand period. Reducing demand at this time of day is particularly
valuable to the utility. The PV system is grid-interactive, producing DC power
that is converted to AC and then fed directly into the local utility distribution
system. The City of Lakeland Department of Electric and Water Utilities in Florida, which
owns and operates one such PV system, allowed connection of a residential PV
system to the utility grid in Florida.
12. High-Efficiency Lighting and Appliances.
Energy Star appliances use less power and LED lighting 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 PV capacity required to meet the
home’s total electrical load.
13. High Efficiency Air-Conditioning and Programmable Thermostat
A programmable thermostat that is set so that the indoor
temperature is allowed to increase overnight and while the house is
unoccupied—decreases the number of hours per day the air conditioner operates.
Running the air conditioner less reduces the total electricity consumption and
lowers utility costs. The combination of efficiency features reduces the
cooling loads so that a downsized air-conditioner will suffice. It has been
shown that a system could be as little as half that of a typical Florida home and
still perform to expectations (1). The unit's
cooling coil air flow 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 operating efficiency.
14. Solar Hot-Water System
In Florida especially, a solar hot water
system is a sensible way to heat water for showers and laundry. The solar hot-water system can supply
as much as 66% of the hot water for occupant needs before power is drawn from
the electrical utility company or a propane hot-water heater that can be used
as a backup is activated.
15. Geothermal Heat Pump
Florida is blessed with an enormous aquifer below it that
keeps a stable temperature in the mid 70F’s all year long. An air conditioner or geothermal heat pump would
rather reject heat to 75 degree water than to 95 degree outside air or to 82
degree soil. Geothermal heat pumps work similarly to air-conditioning except
that during cooling, heat from the house is discharged into the 75deg aquifer
rather than the 90deg outside air. The benefits are lower energy bills, longer
equipment life and no exposed condensing units or cooling towers. Design and
installation has to be done by experts and can be considered an optional extra.
(2)
16. Summery of E-House Features
• Light colored metal roof with large overhangs
• R-30 roof insulation
• R-13 exterior insulation over metal frame system
• Advanced solar control double-glazed windows
• Oversized, interior-mounted ducts
• High-efficiency refrigerator
• High-efficiency LED lighting
• Programmable thermostat
• Solar hot-water system (upgrade)
• Downsized SEER 15.0, variable-speed, 2-ton air conditioner
with field-verified cooling-coil air flow
• 4-kW utility-interactive PV system. (upgrade)
Contact Arno for further information.
This is a very nice concept. I absolutely think this will work amazingly. Good work!
ReplyDeleteGreat Post.
ReplyDeleteYou share Interesting and valuable information.
Thanks for sharing.
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