Wall insulation boards with non-halogenated fire retardant and insulated wall systems

A method of forming a wall of a structure comprising:

• coupling a plurality of structural support together to form a frame;
• attaching a plurality of polyisocyanurate foam boards to an exterior side of the frame to form an insulative exterior wall or surface;
• attaching a plurality of wall boards to an interior side of the frame to form an interior wall or surface, wherein the structural support members, polyisocyanurate foam boards, and wall boards define a plurality of wall cavities;
• and
• positioning an insulation material within at least one of the wall cavities to insulate an interior space of the structure;
• wherein at least one polyisocyanurate foam board includes a polyisocyanurate core produced by reacting components that include:
• an isocyanate;
• a polyol;
• and
• at least one phosphorus containing non-halogenated fire retardant, the polyisocyanurate core forming a sufficiently stable char when exposed to flame conditions in accordance with an ASTM E-84 that enables the polyisocyanurate core to pass the ASTM E-84 test, wherein the polyisocyanurate core foam board comprises an initial R-value of at least 6.4, and wherein the polyisocyanurate core foam board exhibits an ASTM E1354-11b performance equivalent with or better than a similar polyisocyanurate foam board having a halogenated fire retardant tris(2-chloroisopropyl)phosphate (TCPP);
• wherein the polyisocyanurate core comprises an average foam cell size of no more than 200 microns.

A halogen free wall system comprising:

• a plurality of structural support members coupled together to form a frame;
• a plurality of polyisocyanurate insulation wall boards positioned on an exterior side of the frame to form an exterior wall or surface of the wall system, the polyisocyanurate foam insulation boards being produced by reacting an isocyanate and a polyol so that the polyisocyanurate foam insulation boards have an isocyanate index greater than 200, the polyisocyanurate foam insulation boards including a polyisocyanurate core having a halogen free fire retardant, the polyisocyanurate core forming a sufficiently stable char when exposed to flame conditions in accordance with an ASTM E-84 such that the polyisocyanurate core passes the ASTM E-84 test, the polyisocyanurate core comprising an initial R-value of at least 6.5 and an average foam cell size of no more than 200 microns;
• a plurality of wall boards attached to an interior side of the frame to form an interior wall or surface of the wall system, the plurality of wall boards being free of a halogenated fire retardant, wherein the structural support members, the foam boards, and the wall boards define a plurality of wall cavities;
• and
• an insulation material that is positioned within at least one of the wall cavities of the structure, the insulation material being free of a halogenated fire retardant.