Insulated Concrete Forms

Insulated Concrete Forms are a modular structural building system that mimics the Lego concept of pieces that fit together to make a larger structure. The forms are made of either Expanded Polystyrene or Urethane based products. By themselves they will not burn, have been found non-toxic and emit no gasses in place.

Typical Properties of Plastic Foams

EPS XPS Polyurethane Composite Density (lbs/cu ft) 1.35-1.80 1.60-1.80 2.00 21 R-value per inch 4.17-4.35 5.00 5.90 3.00 Compressive strength (psi) 15-33 25-40 30 72 Tensile strength (psi) 18-27 45-75 30 42 Water absorption (%) <3.0 <0.3 2.0 NA Retail cost ($/bd ft) .17 .35 .70 NA Source: Insulating Concrete Forms Association

 

As part of a system, there are provisions made to support the rebar necessary to hold the concrete together after the pour and to support the attachment of siding and interior drywall for direct attachment of these finishes to the system. Many times, the exterior finish will be a troweled on stucco type finish that will add additional fire resistance to the structure. As the structure is reinforced, solid concrete, the structures have a high resistance to windstorms (hurricane and tornado) and to seismic events. The structure is also fire resistant.

Insulated Concrete Forms Efficiency

Since the systems are engineered, they tend to maximize the efficiency of the concrete needed to support a residential structure and eliminate to typical overuse of concrete for the limited loads involved. A standard formed concrete foundation will have a full 6" thickness of concrete wall where as an ICF will have 4"-12" of solid concrete depending on the load you need to engineer for, but you can select that which maximizes the resources for the needs of your specific project.

In addition to having excellent strength characteristics, the insulating qualities of the foam and the solid, construction reduce air infiltration to minimal levels increasing the energy efficiency of the system. The structures also are impervious to attack from insects or mold and are much quieter in urban environments. There is much to recommend them.

Insulated Concrete Forms As a DIY Project

While Insulated Concrete Forms are a project you may undertake as a DIY home building project, get well educated in advance. Because they are the core structure, there is no room for mistakes in planning, and construction of the system so you need to take advantage of all the expert advice you can find from ICF manufacturers and ICF contractors. You would be well advised to hire a professional ICF contractor if you have any doubts as to your ability to do this project, make sure at a minimum that you hire a qualified Engineer or ICF contractor to consult with and most importantly to inspect the forms before you pour the concrete. In many jurisdictions you may be required to have a licensed Engineer inspect the forms before the pour anyway. Spending a few hundred dollars for expert advice could save you thousands of dollars down the road.

The ICF forms are lightweight and assemble like blocks or are sheets that are tied together with pre-designed form ties. The blocks may be simpler for the DIY home builder while the sheet systems can be faster and offer a cleaner surface to stucco over. The system you select will determine the overall complexity.

All of the systems rely on steel reinforcement to tie the structure together, add tensile strength and to distribute temperature stresses throughout the wall. In very cold climes, often times you will see another wall re-framed to the interior to increase the available cavity for adding to overall u-value with sprayed in Icynene foam or standard fiberglass batts and to proved access to install mechanical and electrical systems. Additionally, ICF structure act as a heat sink in the winter, storing heat energy. and can act as a barrier to the transmission of heat energy in the summer months.

Green Aspects of Insulated Concrete Forms

There is some controversy over whether or not concrete supports green building objectives because of the energy intensive nature of its production. But ICF's have been recognized for LEED points on the basis of their insulating capability and when fly ash is used in the concrete they are an excellent example of recycling waste to produce a high strength structure with maximum durability, another LEED characteristic. The structure will last a long time, with lower maintenance costs, reducing future impacts to the environment from having to rebuild the building say 100 years hence.

This system is becoming very popular here in Florida for their Resistance to storms, fire and for their superior thermal performance compared to CMU. They are certainly a very viable system for you to consider for your DIY home building project.

 

 

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