Abstract: An insulative beam and method for its construction. The insulative beam includes two support channels formed from a sheet metal and a block of a plastic material shaped so that each of the two channels wraps at least partly around the block of plastic material. In some embodiments of the invention, the channels extend longitudinally beyond the block of plastic material. If desired to give additional strength to the ends of the insulative beam, the ends are reinforced with angles or channels that fit at the end of the block of plastic material and the angles or channels are welded to the support channels. In other embodiments, the reinforcement is supplied by vertical ribs formed in the web of the support channels. The location of the vertical ribs can be at the ends of the beam or at other areas that are otherwise weakened. Additional reinforcement can be provided by vertical supports within each of the channels.