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| Sustainable Building Sourcebook | ||||||
| Chapter: Materials | ||||||
| Insulated Concrete Forms | ||||||
| CSI Numbers: 04220 Concrete Masonry Units | ||||||
| Introduction: | ||||||
| Insulated Concrete Forms (ICFs) are a family of exterior wall systems that provide the strength of structural concrete walls with the thermal performance of integral insulation and high thermal mass. Also see the Green Building Factsheets for introductions to this and other green building topics. |
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| At-A-Glance Notes: | ||||||
| Technology: | ||||||
| Wall-forms are standard technology. | ||||||
| Suppliers: | ||||||
| All systems have local suppliers or representatives and are readily available. | ||||||
| Cost: | ||||||
| Insulated wall form products have a higher initial material cost than 2x4 construction but provide a superior product. Labor costs can be reduced because these products can be installed by less skilled crews and are less time consuming. | ||||||
| Public Acceptance: | ||||||
| Wall form products are gaining in popularity in the Austin market. Production builders are experimenting with these products. If a major production builder adopts one of these systems, prices could become competitive with 2x4 framing. | ||||||
| Regulatory: | ||||||
| Structures have been built in Austin using all of these systems. Engineered plans may be required for permitting. | ||||||
| Considerations: | ||||||
ICFs can be divided into three categories: fiber-cement block systems, plank or panel wall forms, and precast Autoclaved Aerated Concrete (AAC). All of these systems offer good thermal performance due to their integral insulation and high mass. They also provide excellent acoustical insulation and a minimum two-hour fire rating. Pests such as termites may not eat any of these products but they will burrow into the foam-based panel and plank forms and travel to areas like window and doorjambs or bucks and roof framing where wood is available as a food source. Care should be taken to raise foam panels at least one foot above grade to prevent this infestation. Fiber-cement block systems are systems that use individual blocks or large panels that use some elements common to block systems or CMUs (Concrete Masonry Units). These common elements are an exterior shell made of an insulating material, and interior and end webs that tie the shells together. Fiber-cement block systems are manufactured using a small amount of concrete, usually about 10 percent, as the structural element and a high percentage of either mineralized wood fiber or expanded polystyrene pellets to provide insulating properties. One environmental advantage of these systems is that the wood fiber and the polystyrene can be, and usually are, recycled materials. The fiber-cement block systems have a higher material cost than 2x4 framing, but some of this higher cost is offset by the use of less skilled labor to stack the block, place the structural steel, and pour the concrete fill. These units combine the traditional steps of framing, insulating and sheathing the wall into the process of placing the block and pouring the concrete. The most common and most efficient exterior finish for these systems is stucco, though siding, brick, or stone can also be easily used. The interiors can be plastered or hung with drywall. These block systems are usually impervious to termites because the wood has been mineralized to make it unattractive as a food source and where foam is used, it is in units too small for termites to burrow into. Plank or panel forms are large sheets or planks of polystyrene that are placed on the interior and exterior of the perimeter wall. The forms are held a constant distance apart and the individual elements tied together by plastic or steel ties. Structural steel and concrete are then placed in the form to complete the wall. Most of these systems have fastening surfaces embedded in the foam to allow attachment of drywall, siding, or other materials. These systems can be finished in the same way as 2x4 framing except that screws are used as fasteners rather than nails. Care should be taken to ensure that the exterior foam shell is at least one foot above grade to prevent termites from burrowing into the forms and traveling to wood sources. Insulated Concrete Forms, Fig. 1
Insulated Concrete Forms, Fig. 2
Insulated Concrete Forms, Fig. 3
Precast autoclaved aerated concrete is available in the form of blocks, wall, floor and roof panels, stair treads, and as lentils. AAC block and panel systems offer numerous advantages over standard load bearing wall and floor systems. As an integrated structural system, often erected by a single trade, construction time can be reduced. Being one-fifth the weight of concrete, the system brings far less load to the foundation, offering the possibility of structural cost savings. | ||||||
| Guidelines: | ||||||
Specification for wall formsConventional construction methods Wall forms useUse of these systems eliminates the need for conventional exterior wall framing. Insulated Concrete Forms (ICFs)Most systems stack like blocks and erect easily. Some are in rigid panels on interior and exterior walls connected by metal or plastic ties. Some manufacturers also use expanded polystyrene (EPS) pellets or shredded wood mixed with cement to create the block rather than pure EPS. ICF blocks are typically stacked as exterior walls. Rebar is placed in the cores vertically and horizontally. The cores are poured full of concrete from the top. Manufacturers claim R-values of R-30 or greater when thermal mass is included. Specify that the foam be protected from insects physically and possibly with a borate treatment in the foam. Insects will not eat the foam but may nest in it otherwise. Urethane block wall-forms and extruded polystyrene sheets/panel products are also available. These contain CFCs/HCFCs. Autoclaved Aerated Concrete (AAC) blocksThe blocks are composed of cement, sand, lime, and an aerating agent, which is baked in an autoclave. The result is a very lightweight, insulative, and strong cement block. Blocks are stacked as bricks and held together with a mortar. Interiors and exteriors can be finished in a variety of methods. Use of these systems eliminates the need for conventional exterior wall framing. | ||||||
| Resources: | ||||||
| Professional Assistance: | ||||||
See "Structural Engineers" in Yellow Pages. |
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| Components/Materials/Systems: | ||||||
See "Contractor's Equipment and Supplies, Concrete Additives, Concrete Construction Forms & Accessories, Concrete Contractors, Concrete Equipment and Supplies, Concrete - Ready Mixed, Concrete Reinforcements," in Yellow Pages. ACCO Aerated Concrete Systems, Inc. Applied Concrete Technology Inc. Babb International, Inc. E-Crete Texas Contec Inc. Insulated Concrete Forms (ICFs)Amazon Forms American ConForm Industries American Polysteel Forms Inc. Amvic Building Systems Arxx Building Products Austin Insulating Concrete Forms Inc. Eco-Block, LLC Emega Technologies FutureStone GreenBlock WorldWide Corp. I.C.E. Block Building Systems Insulform Building Systems Inc. Lite-Form, Inc. NUDURA Corporation Poly-Form International Premere Insulating Concrete Forms QUAD-LOCK Building Systems Reddi-Form, Inc. Reward Wall Systems Royal Building Systems Ltd. Therma Foam Inc. ThermoFormed Block Corp. Recycled Concrete Masonry Units (CMUs)Amazon Forms Cempo Forms Inc. K-X Industries Faswall Perform Wall LLC RASTRA of the Americas, L.L.C. Tech Block International, LLC |
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| General Assistance: | ||||||
Autoclaved Aerated Concrete Products Association Cement and Concrete Promotion Council of Texas National Concrete Masonry Association |
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