| FREQUENTLY ASKED QUESTIONS ABOUT INSULATING CONCRETE FORMS (ICS) |
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What are Insulated Concrete Forms?
Insulated Concrete Forms use rigid foam to form concrete walls which are left in place as part of the building envelop. |
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Are ICF walls just for foundations?
No. The same features that make ICFs a good choice for foundations and basements are true for above-grade construction as well. The strength, flexibility, and energy efficiency of ICF walls make sense for all exterior walls. Although in Colorado, VaST prefers to use ICF for foundations only. |
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Are there different types of ICFs?
There are three different types of configurations: flat wall, waffle-grid and screen-grid. Flat wall systems yield a continuous thickness of concrete, like a conventional poured wall. Grid wall systems have a waffle pattern where the concrete is thicker at some points than others. Screen grid systems have widely spaced horizontal and vertical columns of concrete, which are completely encapsulated in foam. Whatever the differences among ICF brands, all major ICF systems are engineer-designed, code-accepted, and field-proven. |
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What are the most typical ICF cavity sizes?
Most ICF companies manufacture forms in 4", 6", 8" and 10" cavity widths. However, some systems that use loose connectors can be built in 2" increments up to 24”. |
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How energy efficient are ICFs?
Based on research performed by Building Works, Inc, houses built with ICF exterior walls require an estimated 44% less energy to heat and 32% less energy to cool than comparable wood-frame houses. In hotter areas, heating savings will be less and cooling savings more. The energy efficient performance comes in large part from the polystyrene foam on the interior and exterior of ICF walls, which range from R-17 to R-26, compared to wood frame’s R-9 to R-15 walls. Also, ICF walls are tighter, reducing infiltration (air leakage) by 50% over wood-frame homes. |
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Can SIPs be used with ICFs?
Yes. Structural Insulated Panels and ICFs are perfectly suited for each other. SIPs can be anchored to ICF foundations or basements using common framing techniques. SIPs are also a good alternative to above grade ICF walls when the added strength and thermal mass is not required. |
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How much steel reinforcing bar (rebar) is required for ICF walls?
The amount of rebar needed will be determined by the design parameters of the building, as with any concrete wall. ICFs have plastic ties to secure rebar within the cavity while concrete is being poured. |
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Are ICFs a sustainable building material?
Most of the definitions and programs of green building identify energy savings as a key criteria. Operating energy has the greatest environmental impact in any life cycle analysis, so any product which can reduce energy used in heating and cooling a building is very “green.” Additionally, the EPS foam used in ICFs does not produce any CFC’s or HCFCs, and does not contain formaldehyde nor any other gasses which might affect indoor air quality. Both the EPS foam and the concrete are highly durable and have a long service life with no repair or replacement costs. ICF material is very resource efficient and multiple manufacturing facilities bring the product close to the job site. ICF construction generates very little waste, much of which can be recycled on the jobsite. Whenever possible with any concrete wall flyash should be used in the concrete to reduce its carbon footprint. |
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How quiet are ICF walls?
An ICF wall has a sound transmission classification of approximately STC 50, which is twice as high as a typical wood-framed wall. Loud noises outside a ICF building will be reduced to a whisper inside the building. |
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How do ICF walls fare with termites and other insects and even rodents?
EPS provides no food value for termites or rodents. Whether wood frame construction or ICFs, local building codes do require methods for protecting foam below-grade in high termite areas, which are specifically outlined in the International Residential Code. The same prevention measures used for wood frame construction can also be used for ICFs. The advantage with ICFs is that the termites can't affect the structural integrity of the building since it is made of concrete. |
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Do you waterproof ICF walls?
As with any form of below-grade construction, waterproofing is required. Recommended waterproofing of ICFs consists of a protective sealant to the EPS foam, coupled with a drainage mat surrounding the foundation wall. A drain at the footing is recommended and may be required by code. |
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How are utilities installed?
The points at which utilities connect to the building should be identified prior to the pour. This will allow for conduits to be placed through the wall so that the utility can enter. Once the concrete is poured and cured, channels or grooves are cut directly into the form using and electric hot knife or router. Plumbing and electrical lines are then inserted into the grooves and covered by drywall. |
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How is drywall attached?
Drywall is commonly fastened to plastic ties within the foam with drywall / gypsum screws. An EPS compatible adhesive may be used in addition. |
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How are exterior finishes attached?
Stucco (acrylic or cementitious) is adhered directly to the foam after rasping it. Wood, plastic or metal cladding is mechanically fastened to plastic ties or, if needed, to continuous fastening strips within the ICF panels. Stone and brick are attached according to design specifications (e.g. with brick ledges and brick ties). |
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