Pre-insulated prefab wall panel

A pre-insulated prefab wall panel for constructing prefab buildings, comprising:

• a rectangular wall frame having nominal 2".times.4" top and bottom rail members, and a plurality of nominal 2".times.4" stud members spaced at about 16" apart and aligned between said top and bottom rail members, said rectangular frame having an overall height of about 953/4" and an overall length of about 16 ft;
• an expanded polystyrene boardstock having a thickness of about 3", affixed to a first side of said rectangular wall frame, thereby defining with said top and bottom rail members and said plurality of stud members a plurality of rectangular cavities, wherein each cavity has a depth of a thickness of one of said stud members, said boardstock being affixed to said rectangular wall frame by means of a plurality of wood straps aligned along said stud members, and nails through said wood straps, said boardstock and into said stud members, said boardstock extending along said height of said rectangular wall frame below said bottom rail member a distance of about between 12" and 14", and extending along said height of said rectangular frame above said top rail member a distance of about a thickness of said top rail member;
• a layer of polyurethane foam covering a portion of said cavities adjoining said boardstock, said layer of polyurethane foam having a thickness of about between 1" and 11/2";
• and
• a top plate member affixed in a temporary fashion to said rectangular wall frame over said top rail member, said top plate member being substantially similar in length and cross-section as said top rail member.

A method for manufacturing a prefab wall panel comprising the steps of:

• assembling an opened structural wall frame on a horizontal flat surface;
• applying a first bead of polyurethane foam on a periphery of said structural wall frame;
• covering said structural wall frame with a polystyrene boardstock;
• fixing said boardstock to said structural wall frame with strap members and nails through said strap members, said boardstock and into said structural wall frame;
• turning said structural wall frame upwardly in a generally vertical orientation;
• spraying a layer of polyurethane foam having a thickness of about between 1" and 11/2" through said opened structural wall frame and against an underside of said boardstock.