Green Term Defined: Insulated Concrete Form

Green Term Defined: Insulated Concrete Form

Insulated concrete form (ICF) is a wall building system made of reinforced concrete and most commonly rigid thermal insulation. The forms are stack and have the appropriate amount of steel reinforcing added vertically or horizontally. The ICF’s are then filled with concrete.


Insulated concrete form are similar to the concept of legos. Each manufacturer has a type of interconnected system so that allow the blocks to lock in place before the concrete is poured. Insulated concrete forms can be used for any building type.

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After the concrete is in place, the insulated concrete form has significant thermal properties, soundproofing, fire resistive characteristics, and durability. ICF blocks are made by many different companies and have different characteristics. Some fold for easy shipping or are put together on site and some are blocks when they arrive. There are blocks that have graphite in them to deter insects from destroying the foam layer. There are blocks that use concrete with wood fiber for the outer walls, some using rigid foam, and some use cellular concrete. Each insulated concrete form has pros and cons, but all offer a superior wall system for many building types.

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What are the options for an energy efficient walls system?

There are many ways to build a thermal envelope for a high performance wall system. Which solution is right for your building is a question that should be answered through the design phase. Understanding all the options is an important first step. The most basic decision should be the thermal performance, but there are many other considerations such as air tightness, water and vapor implications, and available knowledge of the system.

DSC06071Insulated Concrete Forms (ICF) – stackable, permanent concrete forms that have insulation on the outer and inner sides. Concrete is pumped into the cavity to create walls that have higher insulation values than standard pour concrete walls. This system is very air tight which adds to the thermal performance.

Structurally Insulated Panels (SIPS) – high performance building system for residential and light commercial construction. The panels consist of an insulating foam core sandwiched between two structural facings, typically oriented strand board (OSB). This system can come with precut window and door openings or they can be cut in the field.

2 x 6 Wood Studs with Spray Foam – a traditional framing method modified for high performance. The extra 2″ of insulation space adds to the thermal performance and the use of open cell spray foam offers an air tight construction. The downside remains with each wood stud offering a thermal bridge to the outside.

Triple C Camp - NEST Rebuild, 2010

2 x 6 Wood Studs with Cellulose – a traditional framing method modified for high performance. The extra 2″ of insulation adds to the thermal performance and the use of cellulose offers a thermal mass inside the walls. The downside remains with each wood stud offering a thermal bridge to the outside and the difficulty with creating an air tight barrier.


2 x 6 wood stud with 1″ Exterior Polyiso – Taking the 2 x 6 studs with either spray foam or cellulose to a higher level of performance, this strategy can be made air tight and eliminates thermal bridges.


ThermaSteel – The ThermaSteel Building System is a unique patented process utilizing the power of composite technology. A structural grade, opposing double steel framing members with rigid, fire-retardant Modified Expanded Polystyrene Resin (EPS) bonded to the steel frames, forms a thermally broken, light weight composite building component that provides structural framing, insulation, sheathing, and a vapor barrier in one, fast, high-tech step.

Superior Wall – insulated precast concrete wall systems that are custom manufactured to each building’s specification. The product forms a concrete cavity wall panel with concrete studs at 24″ on center attached at the top and bottom with bond beams and the entire assembly is faces with an integral concrete face shell. The wall is reinforced with rebar and polypropylene fibers providing additional structural strength.

There are many more options when trying to design a state of the art home. All have pros and cons and a trained design professional should be consulted to give a holistic analysis before making your decision.