Technology Brief 1
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Concrete Homes Save Energy
Building a concrete home with insulating concrete forms (ICFs) saves energy
and money. The greater insulation, tighter construction and temperature-moderating
mass of the walls conserve heating and cooling energy much better
than conventional wood-frame walls. This reduces monthly fuel bills.
It also allows use of
smaller heating and cooling equipment, saving money in construction.
How much will I save?
Houses built with ICF exterior walls require an estimated 44% less
energy to heat and 32% less energy to cool than comparable frame houses.
A typical 2,000 square foot home in the center of the U.S. will save approximately
$200 in heating costs each year and $65 in air conditioning each year.
The bigger the house, the bigger the savings. In colder areas of
the U.S. and Canada, heating savings will be more and cooling savings less.
In hotter areas, heating savings will be less and cooling savings more.
The smaller heating and cooling equipment needed for such an energy-efficient
house can cut construction costs by an estimated $500 to $2000. The biggest
equipment savings come with the houses that have the most energy savings.
How do we know all this?
The energy savings estimates are from a study of 58 single-family
houses across the US and Canada.
Half had exterior walls constructed with concrete using ICFs made
of expanded polystyrene (EPS) or
extruded polystyrene (XPS) foam.
The other half were neighboring houses with wood-frame walls. All
houses were less than 6 years old.
The researchers compared the energy bill of each concrete house
to its frame counterpart, carefully correcting for important differences to get an “apples-to-apples” comparison.
Estimates of equipment savings are actual numbers reported by contractors
who build ICF houses.
Where do the savings come from?
Insulating values for ICF walls using polystyrene foam are R-17 to
R-26, compared to wood frame’s R-9 to R-15. ICF walls
are expected to cut conduction losses through foundation and above-grade
walls in half. And ICF walls are tighter. In tests, they averaged
about half as
much infiltration (air
leakage) as wood-frame homes.
The energy efficiency of ICF houses has been independently verified
by other agencies. They compared
the energy use of single family houses with various exterior walls
including ICF, concrete
masonry and wood framing. The results show that in almost all climates
across the US
and Canada, concrete homes use less energy for heating and cooling.
But ICF walls do more than cut down on energy loss. Concrete gives
them the heat-absorbing property, “thermal mass,” the ability
to smooth out large temperature swings. It keeps the walls warmer
when the outdoor temperature hits its coldest extreme and cooler
when the outdoor temperature is
hottest. The walls “add back” heat or cooling, which contributes
about 6% of the needed energy to
the house for free.
Since the energy needed is less, furnaces and compressors that
heat and cool can be smaller. And
the more the energy savings, the greater the possible reduction
in equipment size —and cost.
Estimating the size of heating and cooling equipment for concrete
homes is complicated because the
effect of thermal mass must be simulated in a computer program.
But the software tool “HVAC Sizing
for Concrete Homes” takes care of the difficult calculations. All
you have to do is enter information
about the house, like location, house size and wall construction.
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What's the bottom line?
In planning a new home, you can estimate that building with
ICFs will save hundreds of dollars per year in energy costs.
You may also save hundreds or thousands of dollars in construction
costs for heating and cooling equipment. Talk with an ICF homebuilder
for estimates.
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More Information?
Energy
Comparisons of Concrete Homes vs. Wood Frame Homes
RP119 - $10
Thermal Mass Comparison of Wall Systems
CD026 - $20
HVAC Sizing Software for Concrete Homes
CD044 - $59.95
Concrete Homes Helpline: (888) 333-4840
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