Abstract: Foam extrusion apparatus and methods employing a vacuum chamber at reduced pressure into which foamable material is continuously extruded, hardened and cut to length, means for inventorying a plurality of successively cut lengths in a second chamber then at such reduced pressure, and means for discharging the inventory from the second chamber to the outside after the second chamber has been brought to atmospheric pressure without affecting the reduced pressure in the vacuum chamber. Stacking devices are employed to inventory the cut lengths in either a vertical or horizontal stack for transfer as a stack into and/or out of the second chamber. Provision also is made for accumulating the boards in close but spaced facial relationship with substantially the entire surface areas of the cut lengths exposed to the reduced pressure prior to stacking and discharge to the atmosphere.