Washington Administrative Code › Title 51 - Enterprise Services, Department of (Building Code Council) › Chapter 51-11C - State Building Code adoption and amendment of the 2021 edition of the International Energy Conservation Code, Commercial › Section 51-11C-40391 - Section C403.10-Construction of HVAC system elements

Current through Register Vol. 24-14, July 15, 2024
C403.10
Construction of HVAC system elements.
Ducts, plenums, piping and
			 other elements that are part of an HVAC system shall be constructed and
			 insulated in accordance with Sections C403.10.1 through C403.10.3.1.
C403.10.1
Duct and plenum insulation
			 and sealing.
C403.10.1.1
Ducts,
			 shafts, and plenums conveying outdoor air.
Shafts and plenums conveying
			 outdoor air from the exterior of the building to the mechanical system shall
			 meet all air leakage and building envelope insulation requirements of Section
			 C402, plus building envelope vapor control requirements from the
International Building Code
.
Ducts conveying outdoor air shall be insulated continuously
				from the building exterior to an automatic shutoff damper or heating or cooling
				equipment. Duct surfaces shall be insulated with the minimum insulation values
				in Table C403.10.1.1. Duct surfaces included as part of the building envelope
				shall not be used in the calculation of maximum glazing area as described in
				Section C402.4.1.
EXCEPTION:
Outdoor air ducts serving individual supply air units
						  with less than 2,800 cfm of total supply air capacity, provided these are
						  insulated to the minimum insulation values in Table C403.10.1.1.
Table C403.10.1.1 Outdoor Air Ductwork
				Insulation
Duct system
Duct Location and
						  Use
Climate Zone
Airflow
Minimum Installed Duct Insulation
R
-valuea,b
Notes
Outdoor Air
Inside conditioned space and upstream of automatic
						  shutoff damper
4C and 5B
[GREATER THAN EQUAL TO] 2800 CFM
R-16
See Section C403.10.1.1 for additional
						  requirements
Outdoor Air
Inside conditioned space and downstream of automatic
						  shutoff damper to HVAC unit or room
4C
[GREATER THAN EQUAL TO] 2800 CFM
R-8
Outdoor Air
Inside conditioned space and downstream of automatic
						  shutoff damper to HVAC unit or room
5B
[GREATER THAN EQUAL TO] 2800 CFM
R-12
Outdoor Air
Inside conditioned space
4C and 5B
[LESS THAN EQUAL TO] 2800 CFM
R-7
See Exception 1 to Section C403.10.1.1 for additional
						  details
a Insulation
R
-values, measured in
				h·ft2·°F/Btu, are for the
				insulation as installed and do not include film resistance. The required
				minimum thicknesses do not consider water vapor transmission and possible
				surface condensation. Insulation resistance measured on a horizontal plane in
				accordance with ASTM C518 at a mean temperature of 75°F at the installed
				thickness.
b See
International
				Mechanical Code
Sections 603.12 and 604 for further details on duct
				insulation requirements.
C403.10.1.2
Other supply and return
			 ducts.
All other supply and return air ducts and plenums shall be
			 insulated with a minimum of R-6 insulation where located in unconditioned
			 spaces, and where located outside the building with a minimum of R-8 insulation
			 in Climate Zone 4 and R-12 insulation in Climate Zone 5. Ducts located
			 underground beneath buildings shall be insulated as required in this section or
			 have an equivalent
thermal distribution efficiency
.
			 Underground ducts utilizing the
thermal distribution
			 efficiency
method shall be listed and labeled to indicate the
R
-value equivalency. Where located within a building envelope
			 assembly, the duct or plenum shall be separated from the building exterior or
			 unconditioned or exempt spaces by minimum insulation value as required for
			 exterior walls by Section C402.1.3.
EXCEPTIONS:
1.Where located within equipment.
2.Supply and return ductwork located in unconditioned
						  spaces where the design temperature difference between the interior and
						  exterior of the duct or plenum does not exceed 15°F (8°C) and are
						  insulated in accordance with Table C403.10.1.2.
Where located within conditioned space, supply ducts which
				convey supply air at temperatures less than 55°F or greater than 105°F
				shall be insulated with a minimum insulation
R
-value in
				accordance with Table C403.10.1.2.
EXCEPTION:
Ductwork exposed to view within a zone that serves that
						  zone is not required to be insulated.
Where located within conditioned space, return or exhaust air
				ducts that convey return or exhaust air downstream of an energy recovery media
				shall be insulated with a minimum insulation
R
-value in
				accordance with Table C403.10.1.2.
All ducts, air handlers, and filter boxes shall be sealed.
				Joints and seams shall comply with Section 603.9 of the
International
				Mechanical Code
.
Table C403.10.1.2 Supply, Return, Exhaust and Relief Air
				Ductwork Insulation
Duct system
Duct Location and
						  Use
Climate Zone
Minimum Installed Duct Insulation
R
-valuea,b
Notes
Supply air or return air
Outside the building (outdoors and exposed to
						  weather)c
4C
R-8
See Section C403.10.1.2 for details
Supply air or return air
Outside the building (outdoors and exposed to
						  weather)c
5B
R-12
See Section C403.10.1.2 for details
Supply air or return air
Unconditioned space (enclosed but not in the building
						  conditioned envelope)
4C and 5B
R-6
See Section C403.10.1.2 for details
Supply air or return air
Unconditioned space where the duct conveys air that is
						  within 15°F of the air temperature of the surrounding unconditioned
						  space
4C and 5B
R-3.3
See IMC Section 603.12 for additional requirements for
						  condensation control at ductwork
Supply air or return air
Where located in a building envelope assembly
4C and 5B
R-16
Duct or plenum is separated from building envelope
						  assembly with the minimum insulation value
Supply air
Within conditioned space where the supply duct conveys
						  air that is less than 55°F or greater than 105°F
4C and 5B
R-3.3
See Section C403.10.1.2 for details
Supply air
Within conditioned space that the duct directly serves
						  where the supply duct conveys air that is less than 55°F or greater than
						  105°F
4C and 5B
None
See Section C403.10.1.2 for details
Supply air
Within conditioned space where the supply duct conveys
						  air that is 55°F or greater and 105°F or less
4C and 5B
None
Return or exhaust air
Within conditioned space, downstream of an energy
						  recovery media, upstream of an automatic shutoff damper
4C
R-8
Return or exhaust air
Within conditioned space, downstream of an energy
						  recovery media, upstream of an automatic shutoff damper
5B
R-12
Relief or exhaust air
Conditioned space and downstream of an automatic
						  shutoff damper
4C and 5B
R-16
a Insulation
R
-values, measured in
				h·ft2·°F/Btu, are for the
				insulation as installed and do not include film resistance. The required
				minimum thicknesses do not consider water vapor transmission and possible
				surface condensation. Insulation resistance measured on a horizontal plane in
				accordance with ASTM C518 at a mean temperature of 75°F at the installed
				thickness.
b See
International
				Mechanical Code
Sections 603.12 and 604 for further details on duct
				insulation requirements.
c Includes attics above insulated
				ceilings, parking garages and crawl spaces.