Building an ICF (Insulated Concrete Foam) Home

Some builders like to say they can accomplish the same net effect as an Insulated Concrete Foam (ICF) home, and for less money, by sheathing a wood frame house in foam and using foam insulation between the studs.

At the very minimum, however, this approach certainly does not provide the strength of an ICF home. The typical ICF home has a significant amount of rebar and concrete built inside the foam walls. This adds a strength and quietness that you won't find in ICF "imitations."

ICF homes are known for the continuous insulation and low air infiltration. Most well built homes experience about .35 air changes per hour. While really good stick builders can get that figure down to .10 ach, a competent ICF builder can get it down even lower-to a phenomenal .01 ach. That is ten times better than the best stick builders can do, and 35 times better than what most builders will ever accomplish. Air infiltration is a very important factor-even more so than r-value when it comes to comfort, health, and energy efficiency of an ICF home.

The thermal mass in an ICF home creates what is known as the "ICF effect". The concrete in an ICF home actually acts as a large heat sink to store and release energy as needed. The net effect is to "even out" the highs and low temperatures of the day, keeping at the house at a steadier temperature than is possible with other forms of construction. Research has shown that the core temperature of an ICF home significantly lags any change in outdoor temperature. It may take days for the house to adjust-not minutes. A wood home surrounded by foam simply cannot duplicate what the concrete in an ICF home can do. And this is all possible because of the thermal mass of the home.

ICF provides a a significant energy savings over traditional framing on many fronts. The lack of air leaks around the house is one of the biggest advantages. Air leaks are the biggest source of conductive energy loss from furnaces and air conditioners. When air from these devices is not detected in your household thermostat, the appliance has put the temperature to the one you want the appliance will continue to run. Every time the furnace or air conditioner is running, you are spending more money.

If you do have an ICF home, you'll want to determine the need for an air exchanger. Some homes are so airtight, you need a device to ensure that adequate fresh air comes into the homes.