Insulating Characteristics of Cast-In-Place Concrete

Insulating Forms

• One form of cast-in-place is the insulating concrete form or mold. This is a type of cast where the forms, themselves, are designed out of polystyrene insulation. On the external side, a hard layer is used. On the internal side, a soft, more pliable layer is used. The concrete is poured in between them. Here, the insulation is nearly impenetrable, far superior than insulation by itself. If you add pieces of perlite -- a volcanic rock that is one of the most insulating on the planet -- to the concrete, the insulation is almost totally airtight.

Concrete Framing

• Framing a house with wood, fiberglass or steel is common, but these are less insulating than concrete. Using a concrete frame that serves as the cast for the house will reduce energy costs by a significant margin -- up to 20 percent in some cases. The concrete frame is a cast-in-place style where the actual wall scaffolding of the house becomes one large mold. As the insulating forms are the best form of insulation for a house, the cast-in-place scaffolding is the second most insulating method. Since concrete absorbs heat, it extracts heat from the house in the summer and retains heat in the winter, preventing it from radiating through the wall to the outside.

Cast Concrete Properties

• Even additions to the concrete mix, the cast-in-place has an excellent reputation for insulating. The main mechanism for this is that, as the concrete slowly releases its stored heat and the day gets cooler during the night, the “shock” to the heating system is less. The same is the case for the summer. As the hottest part of day comes -- usually about 3 p.m. -- the concrete's continual absorption of heat makes this transition less stressful for the air conditioner. However, the cast itself may delay this process. If the cast remains in place, then the insulating properties of the concrete inside can be negatively effected to the extent that the concrete cannot do its job of absorbing heat. Therefore, it is best if the cast is removed upon curing of the concrete, leaving the concrete directly exposed to the air.

Other Benefits

• Since the cast-in-place process dries the concrete as it is setting in the mold, the concrete will dry and settle better. This means that, as the house settles after the first six months after its construction, there will be fewer cracks. The obvious benefit is that there are fewer places for the hot or cold air to escape. The cast-in-place method, in other words, dries or cures the concrete in a controlled setting.