A wall construction, or other opaque structure of a building, includes a sequence of highly reflective insulation elements that block heat energy exchange across air spaces, combined with material insulation supporting a heat energy highly reflective surface of the highly reflective insulation element. A highly reflective insulation element is formed by enclosing an air space between surfaces, of which one or both of those surfaces is a heat energy highly reflective surface. The heat energy highly reflective surface can be provided by a layer applied to a material. In an opaque building structure, two or more such highly reflective insulation elements, using three or more heat energy highly reflective surfaces, and two or more air spaces, where the material supporting at least one of the heat energy highly reflective surfaces is a material insulator, can improve energy efficiency.

An environmentally friendly, bio-based binder system that is useful for the formation of fiberglass insulation, the system includes: A) an aqueous curable binder composition, which includes a carbohydrate and a crosslinking agent; and B) a dedust composition, which includes a blown, stripped plant-based oil and optionally at least one emulsifying agent. The bio-based binder system is typically heated to form a cured binder system.

A fibrous insulation product having a plurality of randomly oriented glass fibers and a binder composition that holds the glass fibers together is disclosed. The fibrous insulation product has an R-value in the range of 10 to 54 and, after curing, has a density, when uncompressed, in the range of 0.30 pcf to 2.7 pcf. Furthermore, the fibrous insulation product includes glass fibers that, prior to the application of the binder composition, have an average fiber diameter of less than 15 HT a quantity of binder that is in the range of 2% to 10% by weight of the fibrous insulation product.

A fibrous insulation product having a plurality of randomly oriented glass fibers and a binder composition that holds the glass fibers together is disclosed. The fibrous insulation product has an R-value in the range of 10 to 54 and, after curing, has a density, when uncompressed, in the range of 0.30 pcf to 2.7 pcf. Furthermore, the fibrous insulation product includes glass fibers that, prior to the application of the binder composition, have an average fiber diameter in the range of 8 HT to 12 HT and a quantity of binder that is in the range of 2% to 10% by weight of the fibrous insulation product.