Any insulation that has an R value of not less than R35 per inch.
26 U.S. Code § 4053. Exemptions
A prior section 4053, acts Aug. 16, 1954, ch. 736, 68A Stat. 479; Sept. 2, 1958, Pub. L. 85–859, title I, § 104, 72 Stat. 1276, made provision for the imposition of the retailers tax on installment sales, prior to repeal by Pub. L. 94–455, title XIX, § 1904(a)(1)(D), Oct. 4, 1976, 90 Stat. 1811.
2004—Par. (8). Pub. L. 108–357 added par. (8).
1984—Pub. L. 98–369 amended section generally, substituting provisions listing articles on which no tax under section 4051 shall be imposed for former provisions which stated that no tax be imposed under section 4051 on any article specified in subsection (a) of section 4063 and that the exemptions provided by section 4221(a) extended to the tax imposed by section 4051.
Amendment by Pub. L. 98–369 effective, except as otherwise provided, as if included in the provisions of the Highway Revenue Act of 1982, title V of Pub. L. 97–424, to which such amendment relates, see section 736 of Pub. L. 98–369, set out as a note under section 4051 of this title.