Process for producing isocyanate-based foam construction boards

A construction board comprising:

• (i) a foam body having a generally planar shape with first and second planar surfaces, where said foam body is a closed-cell foam body including isopentane and a blowing agent additive contained within the foam body, where the blowing agent additive has a Hansen Solubility Parameter of from 17.0 to 35.0 MPa−0.5, where the blowing agent additive has a boiling point, at one atmosphere, of less than 150° C., where said blowing agent additive is selected from the group consisting of ketones, aldehydes, ethers, esters, halogenated hydrocarbons, and aromatics, where the closed-cell body is a polyurethane or polyisocyanurate foam body prepared by reacting an isocyanate-containing compound with an aromatic polyester polyol, and where the isocyanate-containing compound and the aromatic polyester polyol are reacted at a molar ratio to provide an iso index of at least 220, and where said reacting an isocyanate-containing compound with an aromatic polyester polyol takes place in the presence of a physical blowing agent mixture that includes the isopentane and the blowing agent additive, where the physical blowing agent mixture includes at least 75 wt % of the isopentane, and where the physical blowing agent mixture is substantially devoid of n-pentane and cyclopentane;
• and
• (ii) first and second facers attached to said first and second planar surfaces, respectively.