### Question
How is the term Standard 90.1–2001 defined?


### Answer
The term **Standard 90.1–2001** is defined in *26 U.S.C. § 179D* as the following:

> Standard 90.1–2001 of the American Society of Heating, Refrigerating, and Air Conditioning Engineers and the Illuminating Engineering Society of North America (as in effect on April 2, 2003)

#### Citation:
  - *26 U.S.C. § 179D*
  - Heading: **Subtitle A-Income Taxes > CHAPTER 1-NORMAL TAXES AND SURTAXES > Subchapter B-Computation of Taxable Income > PART VI-ITEMIZED DEDUCTIONS FOR INDIVIDUALS AND CORPORATIONS**

