because it is a better choice for structure that is in direct exposure to the ground or to water.  ICF has the same thermal mass ratings as AAC.  We have used Polystyrene ICF systems, but discovered an ICF system we prefer much better.  We use a product that was developed in the Netherlands, but is also now produced here in the United States.  The company name is Rastra.   We like this product much better than standard ICF systems.  First of all, because it is much more compatible with AAC, but second of all because it is a much more environmentally friendly material.

Rastra is an open cell system like AAC is and so will not trap moisture and vapors like the polystyrene ICF systems.  The Rastra form is made out of Portland Cement and uses recycled polystyrene beads as an aggregate which is what gives its high thermal mass.  Polystyrene is an oil based product which I do not consider to be a green material.  Polystyrene ICF forms are very lightweight and require a great deal of framing material to hold them in place until they are filled with concrete and the concrete is cured.  When you are building all concrete houses what are you going to do with all those framing sticks once the bracing is stripped from the forms?  Therefore, you have all this framing material that ends up being trashed.  Rastra forms are much bigger and heavier than standard ICF forms, so do not need as much temporary bracing material.  Furthermore, Rastra forms do not require as much poured concrete as most ICF form systems to achieve the same strength and thermal mass, so therefore you save significantly in the cost of poured concrete.

We have also done design and consulting for other Earth material type construction such as Rammed Earth Construction and Earth Sheltered Houses.