A funny thing happened to Jesse Savell Jr. on the way to developing a better precast concrete wall system. He discovered an energy-efficient house. He wanted to develop a low-cost competitive wall system using panels that would not crack and could be covered with a stucco finish (popular and prevalent in California) that also would not crack. After about five years of experimentation he arrived at and received a patent for a wall system embodying the concept that each precast wall panel, whether exterior or interior, be an independent structural entity, connected to the others only by nonrigid ties, thus relieving the structure of crack-producing strains. Further, within the panel, a layer of polyurethane would absorb and relieve stresses caused by the differential in the expansion-contraction rates of the concrete and the exterior stucco between which the polyurethane would be sandwiched.
It was discovered that on a hot, 100-degree-F California day, the interior of the house built using this system was a pleasant 70 degrees F. The layer of polyurethane, which was introduced originally to relieve cracking stresses between concrete and stucco, was also serving to insulate but in a different way. Insulation usually is applied to the interiors of walls; but in this house, it was applied outside the concrete walls so that the house was in effect wrapped in a cocoon of insulation. (The conventional insulation batts in the wood truss ceiling-roof system completed the cocoon.) With several more of the houses completed, the startling, energy-efficient aspects of the discovery became more apparent, with conservative estimates putting heating and cooling savings at 60 percent or more compared with conventional wood-frame construction.
This article discusses panel construction, site preparations, and erection sequence of the system.