The double wall process has been in use in Europe for many years. The walls consist of two wythes of concrete separated by an insulated void. The most commonly specified thickness of the wall panels is 8 inches. The walls can also be built to 10 and 12 inches thick if desired. A typical 8-inch wall panel consists of two wythes (layers) of reinforced concrete (each wythe is 2-3/8 inches thick) sandwiched around 3-1/4 inches of high R-value insulating foam.

The two wythes of the interior and exterior concrete layers are held together with steel trusses. Concrete sandwich panels held together with steel trusses are inferior to those held together with composite fibreglass connectors. This is because the steel creates a thermal bridge in the wall, significantly reducing the insulative performance and reducing the ability of the building to utilise its thermal mass for energy efficiency.

There is also the risk that because steel does not have the same expansion coefficient as that of concrete, as the wall heats and cools, the steel will expand and contract at a different rate to the concrete, which can cause cracking and spalling (concrete "cancer"). Fibreglass connectors that are specially developed to be compatible with concrete significantly reduce this problem.[12] The insulation is continuous throughout the wall section. The composite sandwich wall section has an R-value exceeding R-22. The wall panels can be made to any height desired, up to a limit of 12 feet. Many owners prefer a 9-foot clear height for the quality of look and feel it affords a building.