Q: Do JM duct insulations compoly with BOCA requirements?
A: The National Building Code and the National Mechanical Code, written by BOCA (Building Officials and Code Administrators) are generally used in the northeastern United States. The most recent issue of the National Mechanical Code is 1993; it is not being updated because it is to be replaced by the International Mechanical Code.
When used for their intended purpose and when selected so that the R value requirements are met, Johns Manville duct insulation products comply with the requirements of the National Mechanical Code. The following are the major requirements from the 1993 National Mechanical Code:
Duct board:
UL 181 class 0 or 1.
Duct wrap and duct lining:
Flame spread rating of 25 or less, and smoke developed rating of 50 or less as composite.
Shall not flame, glow, smolder or smoke when tested by ASTM C 411 at 250 °F.
Must be labeled with R-value and FHC.
R-value:
The minimum R-value for insulation used on ducts located in unconditioned spaces is calculated as follows:
R = (ti - to) / 15
ti; temp of air in duct
to: temp of air surrounding duct
No insulation required for (ti - to) is 25 °F or less.
For ducts in uninsulated attics the design surrounding air temperature is given in Table M-306.3.2:
|
Table M-306.3.2 Residential Attic Temperatures |
|
Roof slope |
Degrees F |
|
Summer conditions
5 in 12 and up
3 in 12 to 5 in 12
less than 3 in 12 |
130
140
150
|
|
Winter conditions
All slopes |
10 F above outdoor design temp.
|
