Polyurethane Foam - Any of a class of very versatile polymers that are made into flexible and rigid foams, fibres, elastomers (elastic polymers), surface coatings, and adhesives. They are produced by reacting a diisocyanate (a compound with two functional groups of the type — NCO) with a diol (a compound with two hydroxyl, or — OH, groups). Foamed polyurethanes, used for insulation are made with organic compounds containing carboxyl groups, causing a reaction that liberates carbon dioxide bubbles throughout the product.

Spray Polyurethane Insulation - Any of a class of very versatile polymers that are made into flexible and rigid foams, fibres, elastomers (elastic polymers), surface coatings, and adhesives. They are produced by reacting a diisocyanate (a compound with two functional groups of the type — NCO) with a diol (a compound with two hydroxyl, or — OH, groups). Foamed polyurethanes, used for insulation are made with organic compounds containing carboxyl groups, causing a reaction that liberates carbon dioxide bubbles throughout the product.

Flat Roof - A type of covering of a building. In contrast to the sloped form of a roof, a flat roof is horizontal or nearly horizontal. Materials that cover flat roofs should allow the water to run off freely from a very slight inclination.

Barrel Roof - A roof or ceiling having a semicylindrical form.

R Value - A measure of thermal resistance used in the building and construction industry. Under uniform conditions it is the ratio of the temperature difference across an insulator and the heat flux (heat flow per unit area, ) through it. The bigger the number, the better the building insulation's effectiveness.