Insulated Concrete Forms (ICFs)

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    Construct exterior walls with insulated concrete forms (ICFs) that provide insulation without thermal bridging, as well as air sealing, a drainage plane, and high structural strength.
    Scope

    Construct exterior walls with insulated concrete forms (ICFs) that provide insulation without thermal bridging, as well as air sealing, a drainage plane, and high structural strength. 

    • Install ICFs according to manufacturer’s specifications to provide a continuous air barrier and thermal boundary.
    • Seal all seams according to manufacturer’s specifications to provide a weather-resistant barrier and drainage plane.

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Single-Family New Homes, and Indoor airPLUS.

    Description

    Insulated concrete form (ICF) construction combines concrete and rigid foam for walls that are thick, sturdy, and continuously insulated. Studies comparing ICFs with stick-frame construction have shown that in otherwise identical homes, the ICF houses had a 9% better whole-wall R-value and were 10% more airtight (Christian 1996). ICF walls have almost no thermal bridging in the wall itself and, with proper design details, thermal bridging can be almost eliminated at the rim joist as well (Petrie et al. 2003; Desjarlais et al. 2002).

    ICFs are typically made of pre-molded blocks or panels of rigid foam, which are assembled on site to create wall forms into which concrete is poured (Figure 1). The foam forms stay in place, providing permanent insulating foam layers on the interior and exterior of the wall. Foam blocks are typically comprised of two 2-inch-thick, 16 by 48-inch rectangles of foam that are connected by plastic, metal, or foam ties. The ties hold the foam panels 6 or 8 inches apart during the pour and remain in place afterward. The blocks are stacked like bricks to create the wall forms for the concrete. Steel rebar is added to the cavities for additional strength (Figure 2). Some ICFs come with plastic nailing strips embedded in their exterior surfaces. The foam is typically expanded polystyrene (EPS). Some ICF products use extruded polystyrene (XPS) foam, which is stronger but more costly. A few products are made with recycled foam or wood. Some ICF walls consist of two layers of concrete sandwiching a central layer of foam.

    ICFs provide continuous wall insulation from the roof to footing with very little thermal bridging; the ICFs in this home in Las Vegas provide R-40 wall insulation.
    Figure 1. ICFs provide continuous wall insulation from the roof to footing with very little thermal bridging; the ICFs in this home in Las Vegas provide R-40 wall insulation (Source: Department of Energy).

     

    The ICF consists of wall forms made of rigid foam blocks or panels that are held in place with plastic or metal spacers and reinforced with metal rebar.
    Figure 2. The ICF consists of wall forms made of rigid foam blocks or panels that are held in place with plastic or metal spacers and reinforced with metal rebar (Source: National Research Council Canada).

    Common types of ICF walls are shown in Figures 3 and 4. A flat ICF wall system is a solid concrete wall of uniform thickness with sheets of insulation forming the interior and exterior surfaces of the system. The waffle-grid ICF wall system is a concrete wall composed of closely spaced vertical (maximum 12 inches on center) and horizontal (maximum 16 inches on center) concrete members with concrete webs between the members. The screen-grid ICF wall system is similar to a waffle-grid ICF wall system without concrete webs in between the vertical and horizontal members. The post and­ beam ICF wall system has vertical and/or horizontal concrete members spaced farther than 12 inches on center.

    Three common ICF wall systems: the flat wall, the waffle wall, and the post-and-beam wall.
    Figure 3. Three common ICF wall systems: the flat wall, the waffle wall, and the post-and-beam wall (Source: Oak Ridge National Laboratory).
    Different types of ICF blocks.
    Figure 4. Different types of ICF blocks (Source: Oak Ridge National Laboratory).

    ICF systems are installed in a manner similar to masonry, starting at the corners and placing a layer at a time to build up the wall. Most manufacturers make specifically molded corner blocks that provide a continuous layer of foam around the corner to reduce thermal bridging there (Figure 5). Window and door openings must be framed with lumber (Figure 6). Lumber blocking is also needed where bearing pockets are required for floor or roof supports. Ledgers can be mounted to the blocks for attaching floor framing.

    The blocks stack to form walls. Special molded corners provide continuous insulation layer at the corners to improve structural strength and minimize thermal bridging.
    Figure 5. The blocks stack to form walls. Special molded corners provide continuous insulation layer at the corners to improve structural strength and minimize thermal bridging (Source: Portland Cement Association).
    Window and door rough openings in the ICF wall are surrounded with pressure-treated wood.
    Figure 6. Window and door rough openings in the ICF wall are surrounded with pressure-treated wood (Source: Oak Ridge National Laboratory).

    Once the forms are in place and braced, and required reinforcement is installed, concrete is pumped into the forms (Figure 7). Even with the bracing, the forms need to be filled at an appropriate rate based on the ICF manufacturer’s recommendations to prevent misalignment and blowouts. Form failures are rare when the manufacturer’s recommendations are followed. Reinforcement in both directions maintains the wall strength. For earthquake-prone areas, reinforcement should be designed per seismic design requirements. A good item to have on hand when the concrete arrives is a blowout repair kit. Unless a self-consolidating concrete mix is used, concrete should be vibrated after pouring to remove trapped air as air pockets can lead to thermal bridging and weaken the cement (ICF Builder 2012).

     

     

     

     

     

    A pumper is used to place the concrete into the foam form walls.
    Figure 7. A pumper is used to place the concrete into the foam form walls (Source: National Research Council Canada).

     

    Depending on the specific system, the walls may allow attachment of exterior and interior wall coverings directly to the wall with little or no modifications to the wall. After finishes are applied inside and out, typical final wall thickness is greater than 1 ft. This means that window and door surrounds may be wider than is typical for frame construction, resulting in deeper window sills.

    How to Install ICFs 

    Stacking (NAHB 2001)

    1. Place dowels (rebar) in footings, foundation wall, or slab as required.

    2. Place temporary braces along the first course to align the ICF forms and to prevent movement.

    3. Set blocks on concrete footings. Concrete can be recently placed and uncured.

    4. Place termite shield.

    5. Complete one course all the way around the building’s perimeter.

    6. Stagger subsequent courses so that vertical foam joints do not line up from one course to the next. Make sure vertical and horizontal cavities line up. Set horizontal and vertical rebar as required.

    7. Cut for openings as required (or cut out after entire wall is built).

      • Install bucks (2x4 or 2x6 wood framing) around the windows and doors as an attachment surface for windows and doors. A buck may be recessed, protruding, or "channel." Use pressure-treated wood for window framing and all other wooden structural components of the house (ICF Builder 2012, ICFA 2008). EPS foam that is not specifically treated to repel termites is not “resistant” to tunneling termites. EPS provides no food value for termites; however, they will tunnel through it searching for food and a place to live. Alternatively, for window framing, use prefabricated plastic or vinyl bucks. Check all dimensions twice to make sure the rough opening can accommodate the actual window size. Enlarging a rough opening after the concrete has set is costly.

    8. Place intermediate floor connections and supports.

    9. Place sleeve penetrations for dryer vents, electrical, HVAC, cable, telephone, solar, and plumbing services, and outside fixtures and outlets.

    10. Locate and mark block beam pockets.

    11. Reinforce and support the block brick ledge (if applicable).

    Bracing 

    1. Brace the wall forms every 6 feet with strong temporary bracing to ensure they stay level, plumb, square, and straight during the concrete pour and to support the weight of the concrete until it achieves the desired strength. Bracing is needed at corners, window and door openings, periodically along the length of walls, and at the top of the forms. Window and door bucks are braced inside horizontally and vertically (see Figure 8). Top braces square the forms and provide a surface to check wall height and cut uneven blocks. Follow manufacturer’s recommendations completely.
      The ICF walls of this home are braced to prepare for pouring the concrete.
      Figure 8. The ICF walls of this home are braced to prepare for pouring the concrete (Source: National Renewable Energy Laboratory).
    2. Place anchor bolts and ledgers as required. Floor system attachment options include ledgers, pockets, embedded joist hangers, or direct bearing. Ledgers may be made of wood that is either pressure treated or installed with a water-resistant membrane (Figure 9). Bolts and ledgers are placed before the pour, with foam cutouts around bolts to allow concrete to back up the ledger. (The ledger face must not "bear" only on foam.) Embedded joists require cutting out the foam and inserting wood spacers before the pour to create a pocket in which to seat the joist. Some code authorities also require the embedded joist to be fire-cut. See details provided by manufacturer.

       

    3. Place sleeves for any services such as wiring and piping.
    4. Foam seal joints (possibly per course) to secure blocks until concrete is poured and to maintain airtight construction.
      Thermal bridging is eliminated at the rim joist with the use of joist ledgers that are anchored in the wall.
      Figure 9. Thermal bridging is eliminated at the rim joist with the use of joist ledgers that are anchored in the wall (Source: Building Science Corporation).

    Pouring (ICF Systems 2013

    1. Go through the pre-pour checklist.
      Pre-pour checklist.
      Table 1. Pre-pour checklist.
    2. Confirm the concrete order with the dispatcher.
      • Make sure the correct amount of concrete has been ordered, trucks are spaced correctly, and the proper mix design and slump are specified.
      • Order a second truck to be shipped when called. Space all subsequent trucks at 45-minute intervals; holding the final truck on call for any adjusted amount.
      • When ordering, tell them your order will be pumped, it is for an ICF wall, and that you will have to send back any trucks that arrive with more than a 6.5” slump. Add water if necessary at the site to correct the proper slump.
      • Order the correct mix. Work with your ready-mix supplier prior to the pour to make sure they understand the concrete specifications and parameters that ICFs require.
    3. Choose the concrete pouring equipment.
      • Use a line pump or a boom pump to place the concrete. Line pumps, also called trailer pumps, are more labor intensive than boom pumps because the hose must be manually moved and lifted into position. The hourly rates for line pumps are much lower than those for a boom pump, but often the total cost is the same, because they take longer to set up, pump, and take down and they require more manpower. Boom pumps, as shown in Figure 10, can get the job done faster if everyone is properly prepared. Boom pumps are specified by their reach. Most residential jobs use 28, 32, or 36 meter booms. If the boom is much longer than needed, place the truck further from the wall to level out the boom and lower the fall of the concrete. 
      • Reduce the hose width to at least 3 inches. If possible, use an elbow, rams horn, or other attachment at the end of the hose to break the fall and collect the concrete coming through the boom. 
      • Use a steady pour rate, not pulsing or stopping and starting. It should take about 20 minutes to pour 8 yards of concrete.
      • Be aware of any overhead power lines when working with boom equipment. Under certain temperature and humidity conditions, electricity can jump from overhead lines to the boom with disastrous consequences. If you have any concern, consult the pump company and request that the local utility company shield the lines during the pour.
        ICF forms are filled with the use of a concrete pumper truck.
        Figure 10. ICF forms are filled with the use of a concrete pumper truck (Source: National Research Council Canada).
    4. Manage the pour.
      • Check the concrete in each new truck when it arrives to make sure that the slump is correct. Make sure the pump operator and each ready-mix driver understand that no water is to be added without your approval. A wetter mix will make their job easier but can impact quality. If the concrete arrives too wet, you have to decide to send the truck back or wait until it tightens up. If you decide to pump, know that you cannot do lifts very high and may have to take more laps around the walls. If you need to increase the slump, one gallon of water will increase one cubic yard of concrete by one inch.
      • Be ready to pour when the trucks arrive.
      • Have adequate manpower on hand. Pump day can be exhausting, don't be light on manpower.
        Table 2. Manpower requirements
        If you are using a boom pump, you will need: If you are using a line pump, you will need:
        1 - pump operator 1 - pump operator
        1 - hose man 1 - hose man
        2 - wall watchers (one inside, one outside) 1 - outside wall watcher
        1 - utility person for emergencies, contingencies, straightening wall, etc 1 - utility person
          2 - or more hose handlers, rolling scaffolding crew, watching the wall, etc.
    5. Have the right tools on hand. A properly equipped team will make the pour easier, more efficient, and result in a cleaner, more professional, finished product.
      Table 3. Equipment Needed
      Slump cone Gloves
      Brooms Hardhats
      5-gallon bucket Eye protection
      Plywood for slump test Long sleeved shirts & long pants
      Trowels Sunscreen
      Hand tools  
      Shovels  
      Rinsing water  
    6. Pour the concrete.
      • Make sure your scaffolding or walk boards (or other method of getting around the top of the wall) are correct and safe. Raise the scaffolding as needed so the hose man is standing at approximately waist height to the top of the wall. If the top of the wall is above the waist, handling the hose is very fatiguing and the hose man will not be able to see both sides of the wall (See Figure 11).
        Scaffolding is continually raised as courses of foam brick are added so that that the pour man can see both sides of the wall during the pour.
        Figure 11. Scaffolding is continually raised as courses of foam brick are added so that that the pour man can see both sides of the wall during the pour.
      • Have a second person with the hose man to tell him where the concrete is in each section and when to move.
      • With the first yard start the fill below a window so you can see the mix and slump; or begin near a corner with a window within 4 feet. Avoid placing concrete directly into the corners. Fill by moving toward the window and watch the concrete fill up to the bottom of the window, then move to the other side of the window starting approximately 4 feet away and fill back toward the window to lock in the other side. As a precautionary measure, you can pump the first yard back into the ready-mix truck and blend it with the 6 or more yards remaining in the mixer, after the pump operator has already primed out.
      • Plan to get beyond the 32-in. level (above the seam of the second course of forms) with the first lift. Most houses, up to a 12-foot wall height, will require three passes for a complete fill.
      • Have someone trail the hose man to scrape and shake any concrete that may build up on the top of the forms or sit on top of the rebar. This will help prevent voids.
      • While filling the walls on the second pass, do not fill too close to the top; stay at least 24 inches down from the top course and do not fill over doors and windows until the last pass. One exception to this rule is that on deep lintels (over 32 inches), you may want to pour a small amount to begin to form the lintel and load the window.
      • For the last pass, to the top of the wall, you may want to increase the slump by adding water. The increase in slump will allow you to more effectively fill the top of the wall and will give you more time to trowel the top of the wall and set straps or anchor bolts. Tap or vibrate the outside of the wall for proper consolidation, especially over lintels where extra rebar and stirrups can prevent good compaction.
    7. Fix blowouts.
      • Pay close attention when pouring to avoid over-pouring and bulges or blowouts. Blowouts in ICFs are simple to fix. Blowouts often occur where the foam is damaged and not patched or when there is too much water in the cement mix.
      • To repair, clean up the spillage and place the broken foam pieces back in the wall. Cover the damaged area with a piece of half-inch OSB and screw the OSB to the furring strips. For larger blowouts, place pieces of OSB on both sides of the wall at the location of the blowout. Clamp them in place with a threaded bar inserted through the wall and both pieces of OSB.
    8. Perform a final inspection and cleanup.
      • Inspect the job to see if you have missed anything.
      • Check to see if the walls have moved (the earlier in the pour you notice a bow, the easier it is to correct).
      • Confirm that you have good fill. Cross-check the amount of yardage you estimated the walls would require with the load tickets, and know how much yardage you may have left over. Having a yard or two extra is less costly than bringing a truck back with one or two yards.
      • Did you over-fill at a door threshold location or forget a beam pocket? It will be easier to dig out the concrete today than it will be tomorrow.

    Installing Utilities and Attaching Cladding and Interior Finish Material

    • Install wiring and plumbing in recesses cut into the foam after the concrete has been poured (Figure 12). Be sure to cover with metal plates to avoid nailing into wires.
      Utilities are commonly recessed into cutouts in the foam after concrete has been poured.
      Figure 12. Utilities are commonly recessed into cutouts in the foam after concrete has been poured. (Source: Portland Cement Association.)
    • Apply waterproofing on the exterior side of any sub-grade structure to prevent water intrusion (see Figure 13).
      Install waterproofing on portions of the ICF that will be below grade.
      Figure 13. Install waterproofing on portions of the ICF that will be below grade. The waterproofed R-25 ICF blocks shown here are installed starting 30 inches below grade to provide a frost-protected foundation and perimeter insulation for the slab floors of this cold climate home (Source: PNNL). 
    • Attach interior drywall and exterior cladding finishes to the flat ends of metal or plastic ties embedded in the rigid foam. Finishes can also be furred out. Gypsum drywall is the most common interior finish and meets the code requirement for a 15-minute fire barrier over plastic foams surrounding living spaces. Exterior claddings are much more varied but regardless of the cladding type, a drainage layer is recommended between the ICFs and the exterior cladding.
    Ensuring Success

    Use crews that are trained in insulated concrete form (ICF) construction. Before concrete is poured, the site supervisor should inspect the ICF forms to ensure that they are properly installed and well supported and should measure to ensure that blocked openings are properly sized and correctly placed for doors, windows, penetrations, and mounting elements for floors and roofs. Infrared scans can be performed during construction to verify that the concrete layer is consistent.

    Climate

    Accommodations must be made when pouring concrete in below-freezing conditions, but once in the forms concrete cures slowly and stays hydrated to produce a very strong assembly.

    Earthquake-Prone Areas

    In areas that are prone to earthquakes, the structure should be built with the appropriate seismic protection. Reinforcing is required for all ICF walls across all Seismic Design Categories.

    Probabilistic Map of Expected Number of Damaging Earthquakes around the U.S.
    Figure 1. Probabilistic map of the expected number of damaging earthquakes around the United States, in a 10,000-year span (Source: USGS 2014). 

     

    Right and Wrong Images
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    Right – ICFs are being installed to create a continuous air and thermal boundary
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Image
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Image
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Image
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Right – ICFs are being installed to create a continuous air and thermal boundary
    Image
    Right – 11-inch ICFs provide R-50 of wall insulation from the footing to the roof on this cold-climate home.
    Right – 11-inch ICFs provide R-50 of wall insulation from the footing to the roof on this cold-climate home.
    Image
    Right – The spacer structure of these ICFs provides supports for attaching the fasteners used to attach the metal studs of the below-grade walls.
    Right – The spacer structure of these ICFs provides supports for attaching the fasteners used to attach the metal studs of the below-grade walls.
    Image
    Right – ICFs provide an insulated form for the concrete of the foundation wall.
    Right – ICFs provide an insulated form for the concrete of the foundation wall.
    Image
    Right – All cuts into the ICF wall for wiring have been sealed with caulk.
    Right – All cuts into the ICF wall for wiring have been sealed with caulk.
    Image
    Right – A paint-on flashing was applied to the window frames of this ICF house before installing the windows.
    Right – A paint-on flashing was applied to the window frames of this ICF house before installing the windows.
    Image
    Right – The insulated concrete forms that are below-grade have a damp-proof coating to prevent moisture seeping into the foundation
    Right – The insulated concrete forms that are below-grade have a damp-proof coating to prevent moisture seeping into the foundation
    Image
    Wrong – The insulated concrete forms at the foundation do not have a damp-proof coating
    Wrong – The insulated concrete forms at the foundation do not have a damp-proof coating
    Image
    Right – Housewrap adds an extra layer of protection to this home’s ICF walls.
    Right – Housewrap adds an extra layer of protection to this home’s ICF walls.
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    A dimpled plastic water barrier protects the insulated concrete form basement walls and carries any ground water down the walls to the footing drain to minimize the opportunity for water intrusion and frost heave.
    A dimpled plastic water barrier protects the insulated concrete form basement walls and carries any ground water down the walls to the footing drain to minimize the opportunity for water intrusion and frost heave.
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    ICF blocks used for the foundation walls consist of two sheets of rigid foam held together by plastic spacers and reinforced with steel bars forming a hollow wall that is filled with concrete for an ultra-efficient foundation system.
    ICF blocks used for the foundation walls consist of two sheets of rigid foam held together by plastic spacers and reinforced with steel bars forming a hollow wall that is filled with concrete for an ultra-efficient foundation system.
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    ICF bricks are stacked to form hollow walls that are reinforced with steel rebar before the concrete is poured in
    ICF bricks are stacked to form hollow walls that are reinforced with steel rebar before the concrete is poured in
    Image
    Insulated concrete forms are hollow foam blocks that are stacked to form walls, reinforced with plastic spacers and steel rebar, and then filled with concrete.
    Insulated concrete forms are hollow foam blocks that are stacked to form walls, reinforced with plastic spacers and steel rebar, and then filled with concrete.
    Image
    Concrete is being poured into the wall forms made by the rigid foam insulated concrete form blocks.
    Concrete is being poured into the wall forms made by the rigid foam insulated concrete form blocks.
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    Reinforced concrete and rigid foam ICF walls can withstand disaster risks such as hurricanes, tornadoes, floods, wildfires, earthquakes, and pests.
    Reinforced concrete and rigid foam ICF walls can withstand disaster risks such as hurricanes, tornadoes, floods, wildfires, earthquakes, and pests.
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    Seams in the ICF block are sealed so the EPS foam surface can serve as the drainage plane; no house wrap is needed.
    Seams in the ICF block are sealed so the EPS foam surface can serve as the drainage plane; no house wrap is needed.
    Image
    The Habitat affiliate makes its own “ICF” foundation walls with rigid foam held in place with wood spacers.
    The Habitat affiliate makes its own “ICF” foundation walls with rigid foam held in place with wood spacers.
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    The ICF foundation wall of this home is covered with metal flashing before the siding is installed.
    The ICF foundation wall of this home is covered with metal flashing before the siding is installed.
    Image
    These ICF homes are blower door tested during construction, before the drywall is installed, when air leaks can be easily sealed.
    These ICF homes are blower door tested during construction, before the drywall is installed, when air leaks can be easily sealed.
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    Wiring runs are covered with canned spray foam to maintain the continuous foam layer that covers the inside and outside of these ICF block walls.
    Wiring runs are covered with canned spray foam to maintain the continuous foam layer that covers the inside and outside of these ICF block walls.
    Image
    Right – 11-inch ICFs provide R-50 of wall insulation from the footing to the roof on this cold-climate home.
    Right – 11-inch ICFs provide R-50 of wall insulation from the footing to the roof on this cold-climate home.
    Image
    Right – Housewrap adds an extra layer of protection to this home’s ICF walls.
    Right – Housewrap adds an extra layer of protection to this home’s ICF walls.
    Image
    Right – The spacer structure of these ICFs provides supports for attaching the fasteners used to attach the metal studs of the below-grade walls.
    Right – The spacer structure of these ICFs provides supports for attaching the fasteners used to attach the metal studs of the below-grade walls.
    Image
    Right – ICFs provide an insulated form for the concrete of the foundation wall.
    Right – ICFs provide an insulated form for the concrete of the foundation wall.
    Image
    Right – All cuts into the ICF wall for wiring have been sealed with caulk.
    Right – All cuts into the ICF wall for wiring have been sealed with caulk.
    Image
    Right – A paint-on flashing was applied to the window frames of this ICF house before installing the windows.
    Right – A paint-on flashing was applied to the window frames of this ICF house before installing the windows.
    Image
    Right – After installing the insulated concrete foundation wall panels, the builder installed underslab rigid foam, which was topped by 4 inches of crushed rock then the poured slab.
    Right – After installing the insulated concrete foundation wall panels, the builder installed underslab rigid foam, which was topped by 4 inches of crushed rock then the poured slab.
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    Right – Rigid foam was attached to the tops of the precast foundation walls to form an insulated edge for the floor slab.
    Right – Rigid foam was attached to the tops of the precast foundation walls to form an insulated edge for the floor slab.
    Image
    Right – Precast concrete basement walls come to the site with integrated insulation and steel-faced concrete studs.
    Right – Precast concrete basement walls come to the site with integrated insulation and steel-faced concrete studs.
    Image
    Right – This home was constructed with ICF blocks that extend from the footer to the roof line, providing consistent thermal resistance for the entire walls of the home
    Right – This home was constructed with ICF blocks that extend from the footer to the roof line, providing consistent thermal resistance for the entire walls of the home
    Image
    Right – A simple stacked rectangular design and well-insulated and air-sealed ICF walls provide for an extremely energy-efficient structure.
    Right – A simple stacked rectangular design and well-insulated and air-sealed ICF walls provide for an extremely energy-efficient structure.
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    Right – Insulated concrete form (ICF) blocks are stacked like bricks, then rebar is set horizontally and vertically in the plastic spacers, then concrete is poured; the rigid foam and spacers stay in place to add support and thermal resistance to the wall
    Right – Insulated concrete form (ICF) blocks are stacked like bricks, then rebar is set horizontally and vertically in the plastic spacers, then concrete is poured; the rigid foam and spacers stay in place to add support and thermal resistance to the wall
    Image
    Right – The foundation of this ICF home was constructed of ICFs that were set in place on a gravel bed, then 3.5 inches (R-36) of closed-cell spray foam was sprayed directly onto the gravel, providing an effective air, vapor, and thermal barrier.
    Right – The foundation of this ICF home was constructed of ICFs that were set in place on a gravel bed, then 3.5 inches (R-36) of closed-cell spray foam was sprayed directly onto the gravel, providing an effective air, vapor, and thermal barrier.
    Image
    Right – Insulated concrete forms (ICFs) provide the insulated stem wall for the slab-on-grade foundation for this SIP house.
    Right – Insulated concrete forms (ICFs) provide the insulated stem wall for the slab-on-grade foundation for this SIP house.
    Image
    Right – These three urban-infill cold-climate homes were built on insulated concrete foundations.
    Right – These three urban-infill cold-climate homes were built on insulated concrete foundations.
    Videos
    CAD
    CAD Files
    ICF straight wall form in several widths
    ICF straight wall form in several widths
    Download: DWG PDF
    ICF stacked 90 degree corners
    ICF stacked 90 degree corners
    Download: DWG PDF
    ICF 90 degree corner forms and dimensions
    ICF 90 degree corner forms and dimensions
    Download: DWG PDF
    ICF 45 degree panel connector
    ICF 45 degree panel connector
    Download: DWG PDF
    ICF brick ledge form
    ICF brick ledge form
    Download: DWG PDF

    Compliance

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    ENERGY STAR Single-Family New Homes, Version 3/3.1 (Rev. 11)

    Rater Field Checklist

    Thermal Enclosure System. 
    3. Reduced Thermal Bridging. 
    3.4 At above-grade walls separating conditioned from unconditioned space, one of the following options used (rim / band joists exempted):17
    3.4.2 Structural Insulated Panels OR; Insulated Concrete Forms OR; Double-wall framing OR;18, 21

    Footnote 17) Mass walls utilized as the thermal mass component of a passive solar design (e.g., a Trombe wall) are exempt from this Item. To be eligible for this exemption, the passive solar design shall be comprised of the following five components: an aperture or collector, an absorber, thermal mass, a distribution system, and a control system. For more information, see: https://www.energy.gov/sites/prod/files/guide_to_passive_solar_home_design.pdf. Mass walls that are not part of a passive solar design (e.g., CMU block or log home enclosure) shall either utilize the strategies outlined in Item 3.4 or the pathway in the assembly with the least thermal resistance, as determined using a method consistent with the 2013 ASHRAE Handbook of Fundamentals, shall provide ≥ 50% of the applicable assembly resistance, defined as the reciprocal of the mass wall equivalent U-factor in the 2009 IECC Table 402.1.3. Documentation identifying the pathway with the least thermal resistance and its resistance value shall be collected by the Rater and any Builder Verified or Rater Verified box under Item 3.4 shall be checked.

    Footnote 18) Up to 10% of the total exterior wall surface area is exempted from the reduced thermal bridging requirements to accommodate intentional designed details (e.g., architectural details such as thermal fins, wing walls, or masonry fireplaces; structural details, such as steel columns). It shall be apparent to the Rater that the exempted areas are intentional designed details or the exempted area shall be documented in a plan provided by the builder, architect, or engineer. The Rater need not evaluate the necessity of the designed detail to certify the home.

    Footnote 21) Double-wall framing is defined as any framing method that ensures a continuous layer of insulation covering the studs to at least the R-value required in Item 3.4.1 of the Checklist, such as offset double-stud walls, aligned double-stud walls with continuous insulation between the adjacent stud faces, or single-stud walls with 2x2 or 2x3 cross-framing. In all cases, insulation shall fill the entire wall cavity from the interior to exterior sheathing except at windows, doors and other penetrations.

    Please see the ENERGY STAR Single-Family New Homes Implementation Timeline for the program version and revision currently applicable in in your state.

     

    DOE Zero Energy Ready Home (Revision 07)

    Exhibit 1 Mandatory Requirements.
    Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
    Exhibit 2, Item 2) Ceiling, wall, floor, and slab insulation shall meet or exceed 2015 IECC levels and achieve Grade 1 installation, per RESNET standards.

     

    2009, 2012, and 2015 International Residential Code (IRC)

    Although insulated concrete forms are addressed in the IRC in Section R611 (R608 in 2015, 2018), thermal bridging is not specifically addressed.

    Section R301.3 specifies the maximum story heights for walls, including insulating concrete form walls. The maximum story height shall not exceed 11 feet 7 inches (3531 mm) and the maximum unsupported wall height per story as permitted by Section R608 tables shall not exceed 10 feet (3048 mm).

    Section R301.2.2 outlines the seismic provisions and requirements for townhouses in Seismic Design Categories C, D0, D1, and D2 and detached one- and two-family dwellings in Seismic Design Categories D0, D1, and D2. Seismic design categories are determined based on spectral response acceleration, SDS, which depends on location and soil conditions. Buildings in Seismic Design Category E shall be designed to resist seismic loads in accordance with the International Building Code, although Section R301.2.2 discusses methods for reclassifying to a lower seismic design category.

    Section R608 (Section 611 in 2009, 2012 IRC) outlines additional requirements for insulated concrete form systems. The IRC limits the applicability of ICFs to buildings with a maximum design wind speed of 130 miles per hour (58 m/s) Exposure B, 110 miles per hour (49 m/s) Exposure C and 100 miles per hour (45 m/s) Exposure D. Use of ICFs is also limited to detached one- and two-family dwellings and townhouses assigned to Seismic Design Category A or B, and detached one- and two-family dwellings assigned to Seismic Design Category C. Buildings outside of that scope shall be designed in accordance with PCA 100 or ACI 318.   

    20152018, and 2021 IRC

    Section R608 outlines additional requirements for insulated concrete form systems. The IRC limits the applicability of ICFs to buildings with a maximum design wind speed of 160 miles per hour (72 m/s) Exposure B, 136 miles per hour (61 m/s) Exposure C and 125 miles per hour (56 m/s) Exposure D. Use of ICFs is also limited to detached one- and two-family dwellings and townhouses assigned to Seismic Design Category A or B, and detached one- and two-family dwellings assigned to Seismic Design Category C. Buildings outside of that scope shall be designed in accordance with PCA 100 or ACI 318.   

    Flat ICF wall system forms must conform to ASTM E2634.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

     

    American Society for Testing Materials (ASTM) E2634-11 

    Standard for Flat Wall Insulating Concrete Form (ICF Systems). This Specification is intended to apply to ICF Systems that will act as permanent formwork for cast-in-place reinforced concrete beams; lintels; exterior and interior, above and below grade bearing and non-bearing walls; foundation; and retaining walls. In addition, this Specification is restricted to ICF Systems with a resultant uniform monolithic concrete core.

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    Case Studies
    Author(s)
    Pacific Northwest National Laboratory,
    U.S. Department of Energy
    Organization(s)
    PNNL,
    DOE
    Publication Date
    Description
    Case study describing a DOE Zero Energy Ready Home 2013 Housing Innovation Award Winner in Winter Park FL that scored HERS 57 without PV or HERS -7 with PV.
    References and Resources*
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.
    Author(s)
    Building Science Corporation
    Organization(s)
    Building Science Corporation
    Publication Date
    Description
    Information sheet summarizing ICF wall construction including the advantages and disadvantages of this construction strategy.
    Author(s)
    Christian,
    Kosny
    Organization(s)
    Oak Ridge National Laboratory
    Publication Date
    Description
    Report proposing a procedure for estimating the whole opaque wall R-value (whole-wall R-value), independent of system type and construction materials.
    Author(s)
    ICF Systems
    Organization(s)
    Massachusetts Building Products
    Publication Date
    Description
    Information sheet including a checklist of steps to follow for pouring concrete.
    Author(s)
    Insulated Concrete Forms Association
    Organization(s)
    Insulated Concrete Forms Association
    Publication Date
    Description
    Document with information on preventing termites when using ICFs.
    Author(s)
    NAHB Research Center
    Organization(s)
    NAHB Research Center
    Publication Date
    Description
    Information sheet with construction details, pros and cons of insulated concrete forms.
    Author(s)
    Owens Corning
    Organization(s)
    Owens Corning
    Publication Date
    Description
    Information sheet with manufacturer specifications about insulated concrete forms.
    Author(s)
    Portland Cement Association
    Organization(s)
    Portland Cement Association
    Publication Date
    Description
    Information sheet discussing the properties and benefits of insulating concrete forms.
    Author(s)
    Gajda,
    Marceau,
    and VanGeem
    Organization(s)
    Construction Technology Laboratories Inc.,
    U.S. Department of Housing and Urban Development
    Publication Date
    Description
    A guide by the U. S. Department of Housing and Urban Development on the HVAC Sizing Methodology for Insulated Concrete Homes.
    Author(s)
    Maref,
    Armstrong,
    Saber,
    Rousseau,
    Ganapathy,
    Nicholls,
    Swinton
    Organization(s)
    National Research Council Canada
    Publication Date
    Description
    Research study evaluating the dynamic heat transmission characteristics through two identical Insulating Concrete Form (ICF) wall assemblies in Ottawa, Canada.
    Author(s)
    Federal Emergency Management Agency
    Organization(s)
    FEMA
    Publication Date
    Description
    Fact sheet providing guidance on alternative building materials and techniques and their application in coastal environments, and discussing Engineered Wood Products, Structural Insulated Panels, Insulating Concrete Forms, Prefabricated Shear Walls and Moment Frames, Sprayed Closed-Cell Foam...
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

    Building Science Measures
    Building Science-to-Sales Translator

    Insulated Concrete Forms (ICFs) = ICF Thermal Blanket

    Image(s)
    Technical Description

    Insulated concrete forms use hollow rigid foam insulation blocks that are stacked like bricks to form walls that are then reinforced with steel rebar and filled with poured concrete. These systems greatly reduce the amount of wood framing in exterior walls. The foam insulation creates a thermal blanket that reduces the heat transfer between the inside and the exterior. The reinforced concrete adds thermal mass for buffering excessive temperatures and provides additional resistance to strong winds, storms, and fire.

    ICF Thermal Blanket
    Sales Message

    ICF thermal blanket construction blocks excessive heat loss and gain though structural framing. What this means to you is less wasted energy along with enhanced comfort and quiet. Knowing there is one opportunity during construction to lock in quality construction, wouldn’t you agree advanced thermal protection is a great investment?

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