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Frequently Asked Questions
ICF's - Insulating Concrete Forms FAQ's

 

Q: What are Insulating Concrete Forms?
A: Insulating Concrete Forms (ICFs) are hollow blocks or panels made of EPS (expanded polystyrene) plastic foam that construction crews stack into the shape of the exterior walls of a residential or commercial building. Workers then add reinforcing steel and fill the gap typically 4" to 8") between the two layers of foam with concrete, which cures and hardens into a monolithic core. The foam panel stays in place. This combination of concrete, steel and foam creates an incredibly strong and energy-efficient structure.

Q: How does the homeowner benefit from this type of construction?
A: Homes built with ICFs offer resistance to natural disasters such as tornadoes, hurricanes, earthquakes, fires and floods. An ICF home can dramatically reduce heating and cooling bills, plus provide an exceptionally comfortable and quiet indoor environment.

Q: What are the design possibilities and/or limitations with ICF?
A: Today's concrete homes can be created with virtually any design or architectural feature. ICF has furring strips every 8 "imbedded in the panel to allow attachment of any finish” such as wood or aluminum siding, brick, stucco and stone on the exterior, and drywall or plaster on the interior. The result is a home that looks like any other structure in the neighborhood but has all the benefits of solid concrete construction.

Q: Does it cost more to build this way?
A: Typically, a home built with ICFs will cost slightly more than a comparable wood-frame home. However, much or all of this cost can be recouped through significantly lower utility and energy bills, insurance savings and downsizing of heating and cooling equipment. An experienced ICF contractor may be able to further reduce the costs of construction.

Q: How much money can I expect to save on my utility bills?
A: A five year analysis undertaken by Dave McIlwaine of Creative Building Products show houses in the Greater Richmond Virginia are have realized monthly heating/cooling bills averaging about a penny and a half per square foot of conditioned space. The larger the house . . .. The larger the potential savings. Some homes are realizing $1,000s per year in savings!

Q: How well do ICF walls hold up in a fire?
A: Experience shows that concrete structures are far more likely to remain standing through fire than are structures built of other materials. Concrete does not break down until it is exposed to thousands of degrees Fahrenheit - far hotter than a typical house fire. In firewall tests, ICF walls were subjected to continuous gas flames and temperatures of up to 2,000°F for as long as four hours. None of the ICF walls ever failed structurally, in contrast to wood-frame walls, which typically collapse in one hour or less.

Q: What is the average R-value of ICF walls?
A: Walls made of ICFs perform, on average, like a wood-frame wall constructed with R-30 insulation. But that's not the whole story. The equivalent R-value performance of ICFs consists of three factors. First is the R-value of the expanded polystyrene. Second, the thermal stability of massive concrete walls reduces the temperature fluctuations and, consequently, the heat load requirements that are common to wood-frame buildings. Finally, air leakage (infiltration) can account for 20 to 40 percent of the heat load requirements of a wood-frame building. ICFs eliminate this air infiltration through the wall assembly. As a result, with the combined performance of the R-value of the expanded polystyrene, the stabilizing effects of the thermal mass of the concrete, and the reduced air infiltration, ICF walls actually perform as high as R-40 or more in some areas of the country.

Q: Won't the foam burn or give off harmful emissions?
A:
The foams in ICFs are manufactured with flame-retardant additives. The National Research Council reviewed the numerous existing studies of fire emissions and concluded that the emissions from polystyrene foams are no more toxic than those of typical softwoods used in home construction.

Q: What about comfort?
A:
Concrete walls built with ICF's effectively buffer a house's interior from the outdoors. The thick ICF sandwich of a massive material (concrete) with a light one (foam) sharply cuts fluctuations in temperature, air infiltration and noise. ICF's keep the inside more comfortable and less drafty than ordinary wood-frame walls. With regard to noise, studies have shown that compared to a typical wood-frame house, only about one-third as much sound penetrates an ICF wall.

Q: How do ICF homes resist tornado and hurricane-force winds?
A:
Debris driven by high winds presents the greatest hazard to homeowners and their property during tornadoes and hurricanes. Recent laboratory testing at Texas Tech University compared the impact resistance of residential concrete wall construction to conventionally framed walls.

Only concrete wall systems, such as ICF's and concrete masonry, successfully demonstrated the strength and mass to resist the impact of wind-driven debris. The wood-frame walls failed to stop the penetration of airborne hazards.

Q: How popular is this building technique?
A:
ICF construction continues to grow at an impressive rate. It is estimated that in 1998, nearly 20,000 homes in the U.S. were constructed with ICF's. It is anticipated that soon more than 100,000 homes will be built annually with ICF exterior walls.

Q: Is this building technique approved by code organizations?
A:
Yes. Every major code organization in the United States and Canada has accepted this construction technique. ICF homebuilding has proven successful in every region and climate. The 2000 and 2003 International Residential Codes have a section on ICF construction.

Q: Can ICF homes be built in earthquake areas?
A:
Yes. If properly reinforced, an ICF home can provide significant protection during earthquakes. If you live in an earthquake zone, you should consult a structural engineer to determine what the reinforcement requirements are in your area.

Q: Why is ICF considered an environmentally friendly method of building?
A:
In a building's life cycle (from construction to demolition), the greatest ecological impact is the amount of fuel needed to heat and cool the home. Insulating Concrete Homes are a preferred environmental choice because of significant savings in natural resources needed to maintain a comfortable temperature.

Q: Is it difficult for subcontractors to work with this material?
A:
No. Subcontractors (such as electricians, plumbers and drywallers) can easily adapt to working in a house with ICF walls. Once they are familiar with the product, many tradespeople actually find it easier than working on a wood-frame home.

Q: Can termites eat through the foam in an ICF wall?
A:
Expanded polystyrene (EPS) has no nutritive value to insects, including termites. If left exposed and untreated, they may attempt to nest in the EPS foam. Foam is approved for use below grade, as well as above grade, by all building codes as long as an approved method of protecting the foam plastic and structure from termite damage is provided. Deciding what constitutes an approved method, however, is left to local code officials.

One measure agreed upon by all parties is the need for a minimum 6" bare concrete or brick strip at grade level. This is required if foam is used below grade or only above grade. This is extremely easy to accomplish with ICF, since it is a panelized system. This creates a solid barrier, forcing the termite to the outside of the foam where it is visible.

Remember, in a solid concrete home there is little to eat. The concrete also acts as a solid barrier to termite infestation inside the home.

Q: Do I need an engineer to review my building plans?
A:
Residential steel reinforcement for Insulating Concrete Forms is covered in Sections R611 of the IRC 2000, 2003 codes. A contractor can use the prescriptive charts to determine the requirements for most residential construction in Seismic Zones A&B, with some additional parameters in C&D. Home designs that fall outside of the parameters (e.g. extra-tall walls, large openings) require an engineer to review the plans. They will ensure that your construction project meets local code requirements as well as ensure proper design loads for hurricanes, earthquakes and other natural environmental conditions. Commercial buildings generally require engineering.

Q: Can radius and angled walls be constructed with ICF ICFs?
A:
Pre-formed 90 and 45-degree corners are available to speed construction since they are the most commonly used corner angles. Rounded walls are easily constructed by miter cutting the form at the proper angle and using foam to join the edges.

Q: When building with ICF, will mold and mildew in my new building be a problem?
A:
ICFs can significantly contribute to a mold-free environment due to the inorganic nature of the material. They also create a very tight building envelope, reducing unintentional air infiltration. In high-humidity environments, interior moisture should then be controlled through the use of spot removal (e.g., bathroom fans) and properly sized air conditioning units that will cycle on long enough to dehumidify the air.

Q: How can I obtain more information on the ICF ICF building system?
A: Simply contact/call us: Thermacrete Construction, LLC at (804) 357-1741 .

 

 
 

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