provides a superior product to using dissimilar retained spacing materials application_number US 201213481556 A description a feature of the present invention is in the structure of the structural insulated panel where insulating foam is fixed in place around the edges of the panel between the two outer layers to form the border and spacers for a cavity which is filled with expanding foam the foam spacer holds the outer layers apart by a prescribed distance and serves to hold the expanding foam within the cavity the foam can be fixed in place by any number of methods which would include gluing stapling nailing or screwing for example additionally the foam spacer could be formed in place by pouring or spraying an expanding foam between the outer layers the foam spacer can also be configured as a tongue and groove pattern so that panels placed into a wall and interlock for good air sealing and structural properties the foam spacer can also be made by cutting strips from a structural insulated panel that has the same total width as the target core of the panel being produced the foam spacer will generally have a hole cut into it on one side to allow the introduction of the foaming insulation the invention would also include smaller holes cut in an edge of a panel to vent the air out of the cavity the use of foam spacers create flexibility in how panels are configured manufactured and used for example foam spacers can be used to introduce conduit into the panel structure panels can be manufactured specially to create a panel full of conduit molded inside the foam these panels can then be cut to produce several spacers with conduit which in turn can be used to assemble hollow core panels.