Storm or Thermal Window or Door Law and Legal Definition

Pursuant to 26 CFR 1.23-2, [Title 26 -- Internal Revenue; Chapter I -- Internal Revenue Service, Department of the Treasury], the terms storm or thermal window and storm or thermal door mean the following:

” (A)(1) A window placed outside or inside an ordinary or prime window, creating an insulating air space.

(2) A window with enhanced resistance to heat flow through the glazed area by multi-glazing.

(3) A window that consists of glass or other glazing materials that have exceptional heat-absorbing or heat-reflecting properties. For purposes of this subdivision (iv), the term "glazing material" does not include films and coatings applied on the surface of a window.

(B)(1) A second door, installed outside or inside a prime exterior door, creating an insulating air space.

(2) A door with enhanced resistance to heat flow through the glazed area by multi-glazing.

(3) A prime exterior door that has an R-value (a measurement of the ability of insulation to resist the flow of heat) of at least 2 throughout.

For purposes of this subdivision, "multi-glazing" is an arrangement in which two or more sheets of glazing material are affixed in a window or door frame to create one or more insulating air spaces. Multi-glazing can be achieved by installing a preassembled, sealed insulating glass unit or by affixing one or more additional sheets of glazing onto an existing window (or sash) or door. For purposes of this subdivision, a storm or thermal window or door does not include any film applied on or over the surface of a window or door.”