Technology Brief 5
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The Quality of Concrete Costs Little More
The many benefits of a concrete house built with insulating concrete forms (ICFs) are available for only slightly more than the cost of ordinary wood frame. ICFs are simple to assemble and they consolidate several construction steps into one. The walls can be economical despite the use of high-quality materials.
What is the "true" cost of an ICF home?
On average, new houses built by experienced contractors cost about
4-7% more than conventional 2x4 wood frame houses of the same design. But
there are cost savings in other areas that will help to offset
some of these first costs as well as provide the homeowner with
significant improvements in day to day operational expenses and
environmental impacts.
Since ICF homes are more energy-efficient, mechanical equipment can be
smaller than in a frame home. This can typically result in at least
1% in up-front savings. So the net extra cost will be about 3 to 6% of the
sale price of the home 1.
Higher quality exterior walls and smaller mechanical systems means less
monthly cost for the homeowner with savings of at least 25% or
more depending on the climate2. Downsized HVAC also
results in reduced greenhouse gas emissions over the life of the
structure compared to less efficient wood-frame construction 3.
What is an "experienced contractor"?
As with any innovative new construction product, the more a crew works with ICFs the more efficient assembling them becomes. ICF wall-building crews report that their costs drop sharply until they have built 4 or 5 houses. After that they continue to realize savings, but at a slower rate.
Mechanical contractors also need experience to size equipment correctly.
If not experienced with homes as
energy-efficient as an ICF house, they will tend to install equipment
sized for a wood frame residence. Systems can be larger than
necessary, do not run efficiently and the buyer loses
potential initial day-to-day cost savings. In addition, excess
moisture can build up in the house, causing unsightly and unhealthy
problems. Helpful computer software is available for correctly
sizing heating and air conditioning systems in concrete homes (see
publication reference below).
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Will homeowners save money living in an ICF home?
Because ICF walls feature thicker unbroken layers of insulation and the mass
of concrete, they provide much better energy performance than conventional
wood frame construction. Computer simulations comparing concrete homes to
wood frame construction have shown the combined effects of higher
R-values, low air infiltration and the impact of concrete's thermal
mass all combine to enable concrete walls to provide significant
operating cost savings. Savings will vary by climate with the inherent
thermal mass benefits having more impact in warmer locations and
the added insulation being more critical in colder areas.
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How can living in an ICF home reduce greenhouse gases?
Life cycle studies show most of the environmental load of a typical home
is from the household use of natural gas and electricity during
the life of the house3. Enclosing a home with more
efficient ICFs means smaller mechanical equipment and lower fossil
fuel consumption during the operating life of the house. This means
the concrete house will generate less greenhouse gases than a comparible
wood frame residence.
Why should I pay more?
Each year, the number of new home buyers who choose to have their houses
built with concrete and ICFs continues to increase. Saving on the
cost of fossil fuel consumption, and reducing emissions is a huge
plus. But they also cite these additional advantages:
Comfort. ICF houses are far less drafty than frame, have far fewer “cold spots”,
and maintain a noticeably more even temperature.
Quiet. Only about one-sixth as much noise travels through an ICF wall. Occupants are pleasantly surprised by the reduction in noise that enters from outside.
Strength. Owners of ICF houses feel less flex in their walls and floors. They notice virtually no vibration when they slam a door. Engineering calculations show the walls are much stronger than frame walls in many ways. Field data show they survive many types of natural disaster better.
Energy efficiency. ICF walls cut an estimated 30-40% off the energy used to heat and cool a house. This means lower energy costs, to the tune of $200-300 per year for a typical home.
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What's the bottom line?
When planning a new house, you can estimate that building the walls
of concrete with ICFs and experienced crews will add about 3 to
6% to the overall cost of the home. The high performance of the
ICFs will provide the concrete homeowner with significant reductions
in energy consumption and emissions while providing a stronger,
quieter and more comfortable home.
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1. “RSMeans Residential Cost Data,” Reed Construction Data, Inc.
2. “Energy Use of Single-Family Houses With Various Exterior Walls,” by
CTL Group for Portland Cement Association, 2001, PCA CD026.
3. “Comparison of the Life Cycle Assessments of an Insulating Concrete
Form House and a Wood Frame House,” by CTL Group for Portland
Cement Association, 2008, Serial
No. 3041.
For More Information The following resources are available from the Portland Cement Association.
To order, call PCA Publications at (800) 868-6733, or click on
the link provided.
Concrete Homes Helpline: (888) 333-4840
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