Surface conductances and resistances for combined
free convection and radiation in air

From ASHRAE (1989), with permission

Conductances given in W/m2·°C)
Resistances given in (m2·°C)/W

Values for still air

Position of surface

Direction of heat flow

Surface emittance

Non-reflective

Reflective

e = 0.90

e = 0.20

e = 0.05

hi

R

hi

R

hi

R

Horizontal

Upward

9.3

0.11

5.17

0.19

4.32

0.23

Downward

9.1

0.11

5.00

0.20

4.15

0.24

Sloping at 45°

Upward

8.3

0.12

4.20

0.24

3.35

0.30

Downward

7.5

0.13

3.41

0.29

2.56

0.39

Vertical

Horizontal

6.1

0.16

2.10

0.48

1.25

0.80

 Values for moving air for non-reflective surface with e = 0.90

Position of surface

Direction of heat flow

hi

R

24 km/h wind (for winter)

Any

34.1

0.030

12 km/h wind (for summer)

Any

22.7

0.044

Notes for both tables: