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Carver Communications - Index

Carver Communications - 9.1.08 - Index

Vol.XXVI, No.17 © Carver Communications, Inc. September 1, 2008
What Exactly Is A Green Home?
By John Friesenhahn
Every day we see more companies
promoting their green products and practices.
John McCain, Barack Obama and T.
Boone Pickens are promoting their plans
to reduce America’s dependence on foreign
oil and to increase our supply of
clean, renewable energy. Closer to home,
we all are feeling the higher cost of gas
and utility bills in our personal budgets. A
shift is occurring in the demand for more
fuel efficient hybrid cars. But, why do we
not demand the same efficiency and performance
from the largest purchase most
people make in their life – their home?
What exactly is a “green” home?
Most people know about Energy Star
Homes which must achieve at least 15%
increased energy-efficiency over a code
built home. Additionally, there are several
national green programs, like LEED-H
(Leadership in Energy and Environmental
Design) or the NAHB Model Green
Home, and local green programs geared to
a particular community, like Build San
Antonio Green, that develop criteria to
review and certify a home’s level of
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“green.” Regardless of the program, common
categories, in addition to energy-efficiency,
are site design, materials and building
practices, water conservation and
health. To be successful, a home must be
designed, built and operate as a system.
The term “building science” has
become a popular label for the system built
approach to design and construct buildings
that are more durable, healthier, more sustainable
and more economical than most
buildings built today. An important and
often misunderstood example in our hot,
humid climate is the selection of a homes
air conditioning system where most people
think bigger is better. However, in a properly
insulated, tight home that has double
pane low-e glass windows and air conditioning
ducts tested for leakage, installing
an oversized air conditioning system will
cause the system to short cycle (turn on
and off in short periods of time). This
reduces efficiency, does not effectively
control humidity and increases wear on the
equipment. Increased humidity not only
affects comfort in a home, but can impact
indoor air quality by maintaining a humid
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environment suitable to mold growth. So,
you spend more money up front to install a
larger system, you spend more money to
operate the system and you are not comfortable,
but the mold spores are happy.
A green home starts by working
with an energy rater to perform a Home
Energy Rating System (HERS) model.
The building specifications, such as insulation,
windows and air conditioning system
among others; performance standards,
such as air infiltration and duct leakage
goals; and the building design details, such
as wall and window areas with orientation,
are entered into a computer model to
determine energy use for the home. The
HERS model provides an index score indicating
the energy use as compared with the
same home built to code minimum standards.
The index score for the code built
home is 100, the maximum Energy Star
qualifying score is 85 and every decrease
of 1 point equates to a 1% energy use
reduction until you get to 0 which would
be a “zero energy” home using energy
generated by renewable sources such as
solar or wind. It is important to test and
inspect the home throughout construction
to insure the end result will match the predicted
goal. Two common tests are the
duct blaster, to measure air conditioning
duct leakage, and the blower door tests to
measure infiltration in the home.
Energy-efficiency is the area most
valued by homeowners because it is easy
to see the payback every month when paying
utility bills. An energy-efficient home
starts with proper framing and structural
details to create a building envelope
(walls, foundation and ceiling) that allows
a continuous thermal barrier (insulation)
and air barrier to be installed. Whether
specifying foam, cellulose or fiberglass
insulation, detailed installation free of
voids, gaps and compression is important
to achieve the rated thermal performance.
Modern technologies, such as Demilec
open cell spray foam, not only make it easier
to fill all voids in walls and ceilings as
the foam expands around pipes and wires,
it creates an impenetrable air barrier. In
comparison, fiberglass batt insulation
costs less, but is more difficult and time
consuming to properly install around pipes
and wires with gaps, voids or compressing
the fiberglass fibers which in reality means
it does not perform. Add energy-efficient
windows with low-emissivity (low-e)
glass, Energy Star appliances and compact
fluorescent light bulbs to the system and a
smaller, “right-sized” high efficiency heating
and air conditioning system can be
installed saving initial cost for the unit,
reducing utility costs and providing more
comfort. After insuring this efficient system
is in place, renewable solar or wind
energy systems begin to make sense.
Water conservation is a hot topic
every summer in San Antonio. Green
homes are designed to conserve this precious
resource indoors and outdoors.
Indoor water conserving features commonly
include structured plumbing systems
that keep water supply piping out of
the foundation and provide a more direct
delivery of water to each fixture; tankless
water heaters; dual flush toilets use an
averaged 1.28 gpf with better performance
than typical 1.6 gpf low flow toilets;
Energy Star dishwashers and washing
machines and low flow plumbing fixtures.
Outdoor conservation includes selecting
landscaping from the SAWS approved
low-water plant list and, if installing an
irrigation system, sod areas are zoned
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