DUCT LENGTH (m)

DUCT LOCATION

0 to 20

21 to

45

46 and longer

*

Type of Insulation

2

3

d 5

Roof or exposed to outside air

C+W

C+W

C+W

Between floor spaces, under floor

spaces and basements, above false

ceilings

A+W**

B+W**

C+W**

Within the conditioned space

None required***

Encased in concrete

None required

*     For description of insulation types A,B,C & W, see Appendix IV

**    W is required only on cooling and cooling/heating applications.

***   When the design dry bulb temperature of fluid inside the duct is below the dew point temperature of air surrounding duct then the A+W type of insulation shall be used.

(Table 13.3 of the Building Code of Pakistan)