surface may be provided on only the exterior side of the poured concrete wall such as to facilitate use of flange 34 of retainer 22 to attach exterior siding to the wall insulating panels can be provided only on the interior side of the wall with flange portion 34 of retaining strip 22 used for attaching interior drywall paneling or the like when the wall system and method of this invention is used for insulating both sides of a poured concrete wall the retaining strips on the exterior side of the wall can be used for securing exterior siding to the wall and the retaining strips on the interior side of the wall can be used for securing drywall or the like in fig7 there is shown an alternative embodiment of the retaining strip 122 retaining strip 122 includes a segmented web portion including a web portion segment 130 a extending between an exterior flange 134 and a parallel interior flange 135 and a second web portion segment 130 b extending from interior flange 152 to an enlarged anchor portion 132 depending on the dimensions of retaining strip 122 and the dimensions of insulating panel 18 insulating panel 18 may be retained between flanges 134 and 152 or flanges 134 and 152 may engage parallel grooves in the edges of adjacent panels 18 as another alternative one or the other of flanges 134 and 152 may be engaged in a groove formed in the edge of an insulating panel 18 while the other flange engages one.