Description

U-factor (Btu/ºF-ft²)

A

Uninsulated single-layer metal swinging doors or non-swinging doors, including single-layer uninsulated access hatches and uninsulated smoke vents: 

1

1.45

Uninsulated double-layer metal swinging doors or non-swinging doors, including double-layer uninsulated access hatches and uninsulated smoke vents: 

2

0.70

Insulated metal swinging doors, including fire-rated doors, insulated access hatches, and insulated smoke vents: 

3

0.50

Wood doors, minimum nominal thickness of 1-3/4 in. (44 mm), including panel doors with minimum panel thickness of 1-1/8 in. (28 mm), and solid core flush doors, and hollow core flush doors: 

4

0.50

Any other wood door:

5

0.60

Uninsulated single layer metal roll up doors including fire rated door

6

1.45

Insulated single layer metal sectional doors, minimum insulation nominal thickness of 1-3/8 inch; expanded polystyrene (R-4 per inch).

7

0.179

Source:  ASHRAE 90.1-2007, Section A7.