Facilities Quality Service
PIPING INSULATION
Topic: A reminder on chilled water piping insulation
ISSUE:
Cellular glass insulation for chilled water piping in humid climates.
BACKGROUND:
On December 24, 1997, Office of Facilities Management (FM) published a Design Alert
FM-187C-DA81 `Insulation for Chilled Water Piping' recommending use of cellular glass
insulation in humid climates, and revised VA Master Specification Section 15250
accordingly. For some reasons, the designers on several projects have not specified
cellular insulation, and this can cause serious problems in the future.
DISCUSSION:
1. Relative humidity exerts intense water vapor pressure on the insulation. Therefore,
this makes impermeability the most critical criteria for insulating material for chilled
water piping in humid climates. The other important properties to consider are,
flame and smoke spread, compressive strength, and thermal conductivity. Just 4%
moisture by volume in insulation can reduce efficiency by 70%. Wet insulation is a
ready medium for mold and mildew growth. ASHRAE recommends a permeability
of 0.10 or less for chilled water systems.
COMPARISON OF INSULATION PROPERTIES
(Based on values from manufacturers literature)
Properties
Cellular glass
Phenolic
Elastomeric
Permeability
0.00
75.00
0.12
0.10
Perm-inch
Flame & Smoke
5&0
25 & 50
17 & 19
25 & 50
ASTM E-84
(pH)
7.0 8.5
NA
1.4 5.2
NA
Compressive
100.00
1.9
25.0
2.0 5.0
Strength (psi)
Thermal
0.32
0.23
0.13
0.27
Btu-in/hr.sq ft.
degrees F
22 June 2000
FM-181A-DA 106
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