Buildings constructed of ICF's have a more even temperature throughout the day and night, fewer drafts, fewer cold spots and hot spots, and a more consistent temperature from floor to ceiling.

• Even temperature: Concrete is a material of high thermal mass. That means it changes temperature slowly. ICF walls, in fact, have about 3-5 times the thermal mass of a conventional wood frame wall. The result is that the temperature of the building tends to be very stable, instead of overheating and getting cold when the furnace (or AC) cycles on and off every half hour.
• Fewer drafts: An ICF wall consists of two layers of a fairly air-tight material (foam or cementitious composite) sealed in the center with concrete. This contrasts with wood frame, which is assembled of many rigid pieces to leave thousands of tiny air gaps. Recent studies of new wood homes show air changes per hour of an average of 0.5. But ICF houses have consistently been measured at much lower change rates (down to .11), for many fewer drafts.
• Fewer hot and cold spots: Most ICF walls include two layers of insulation that are almost completely uninterrupted. The uninsulated portions of wood frame walls usually add up to about 25% of total area. The result is that ICF walls have virtually none of the cold spots or hot spots one feels when walking along frame walls in winter or summer.
• Consistent floor-to-ceiling temperature: Since ICF's have consistent thermal mass and insulation at the floor level and up and down the wall, measurements have shown an air temperature differential in ICF houses from floor level to ceiling level of only 2-3 degrees. The difference can be 2-3 times this in conventional houses.

Only about one-third as much noise gets through an ICF wall as passes through a conventional wood-frame or steel-frame wall. This sharply reduces the annoyance of outside traffic, aircraft, lawn mowers, and storms. Owners say you have to experience it to appreciate it.

The sandwich of concrete and foam is almost ideal for blunting sound. Engineers measure sound passage with the sound transmission coefficient (STC). A conventional wood-frame wall finished on both sides typically scores an STC of 36-38. Various ICF walls have been tested and scored in the high 40's and low 50's. A difference of ten points on the STC scale (like from 38 to 48) corresponds to a reduction in sound transmission of a little over two-thirds. So these results verify what owners have long noticed: one-third or less of the sound gets through.

Studies comparing the fuels bills of ICF houses with similar wood frame houses next door estimate that on average an ICF house will consume 43 percent less energy for heating and 32 percent less for cooling. That works out to $200-400 per year saved on a typical house.

The savings come from the same things that make ICF buildings more comfortable: the high insulation of the foam, the thermal mass of the concrete, and the low air infiltration of the foam-concrete sandwich.

The R-value of ICF forms filled with concrete varies from brand to brand, but is usually about 20. Conventional 2-by-4 wood frame walls may have R-11 or R-13 insulation. But because of the many uninsulated portions the total wall is usually tested at about R-10. So ICF's have about twice the R-value.

Because the concrete's thermal mass evens out temperature fluctuations, ICF's don't have quite as much heating to do during the coldest hours or as much cooling to do during the warmest. According to engineering simulations, this can subtract a further 4-8% from utility bills.

Engineering estimates suggest 20-40% of heating and cooling goes simply to correcting the temperature of air that leaks in from outside. Since ICF buildings reduce infiltration by half or more, that's another 10-20% shaved off the bill.

And the savings are not only in the fuel bill. Because an ICF building has a lower heating and cooling load, the furnace and air conditioner can be smaller. Good heating and cooling contractors regularly realize savings of around a thousand dollars on a typical house.

Concrete is a material for the ages. It is resistant to rust, rot, burning, light, oxidation, and pests. The earliest forms of concrete still survive in structures nearly two thousand years old built by the ancient Romans.

ICF walls have required little or no maintenance or repair. Many buyers in fact choose them because they want not to have to worry about what happens inside their walls.

An ICF house can look like a typical house, or it can have striking features difficult to achieve with conventional construction.

ICF's can take any conventional finish--stucco, brick, stone, clapboard, hardboard, vinyl--just about anything that goes onto frame buildings. And the cost and time of installing these finishes is about the same or, in some cases, less.

ICF's can also have any common footprint--from the simplest rectangle.

But because foam is readily workable, many uncommon shapes are also possible at a lower cost than they would be with conventional walls. Curves and irregular angles are some of the favorites that a skilled ICF crew can produce relatively easily.