Air Conditioning Duct Insulation Thickness Table

Haili admin

Sep/08/2025

Air Conditioning Duct Insulation Thickness Table provides a clear reference for selecting the proper insulation thickness in HVAC systems. Correct insulation not only minimizes energy loss and improves cooling efficiency, but also helps control condensation, reduce noise, and extend the service life of ducts. The required thickness usually depends on factors such as duct size, operating temperature, ambient conditions, and energy-saving standards. By following an insulation thickness table, engineers and contractors can ensure compliance with regulations, achieve optimal thermal performance, and maintain indoor comfort in both residential and commercial projects.

Chilled water pipeline (≥5℃)
	Flexible foam rubber-plastic shell (mm)		Glass wool shell (mm)
	Nominal pipe diameter	Thickness	Nominal pipe diameter	Thickness
Inside the room ceiling, computer room	15～25	25	15～25	25
	32～80	30	32～80	30
	≥100	35	≥100	35
outdoor	15～25	35	15～25	30
	32～80	40	32～80	35
	≥100	50	≥100	40

Hot water, hot and cold combined pipe (5～60℃)
	Flexible foam rubber-plastic shell (mm)		Glass wool shell (mm)
	Nominal pipe diameter	Thickness	Nominal pipe diameter	Thickness
Inside the room ceiling, computer room	≤50	30	≤40	35
	70～150	30	50～100	40
	≥200	35	125～250	45
			≥300	50
Outdoor	≤50	35	≤40	40
	70～150	35	50～100	45
	≥200	40	125～250	50
			≥300	55

Hot water, hot and cold combined pipe (0～95℃)
	Polyurethane rigid foam (direct burial) (mm)		Glass wool shell (mm)
	Nominal pipe diameter	Thickness	Nominal pipe diameter	Thickness
Inside the room ceiling, computer room	≤32	30	≤50	50
	40～200	35	70～150	60
	≥250	45	≥200	70
Outdoor	≤32	35	≤50	60
	40～200	40	70～150	70
	≥250	50	≥200	80

Ice storage pipeline (≥-10℃)
		Flexible foam rubber(mm)	Polyurethane foam (mm)
Indoor	15～40	35	30
	50～100	40	40
	≥125	50	50
	Plate heat exchanger	35	-
	Tanks and tanks	60	50
Outdoor	15～40	40	40
	50～100	50	50
	≥125	60	60
	Tanks and tanks	70	70

Air conditioning condensate pipe
	Flexible foam rubber-plastic shell (mm)	Glass wool shell (mm)
Air-conditioned room ceiling	10	10
Non-air-conditioned room	15	15

Air conditioning ducts
		Flexible foam rubber-plastic board (mm)	Glass wool board, felt (mm)
Supply air temperature ≥14℃	In a non-air-conditioned room	20	40
Supply air temperature ≥14℃	In an air-conditioned room	20	30
Supply air temperature ≥4℃	In a non-air-conditioned room	25	50
Supply air temperature ≥4℃	In an air-conditioned room	25	40

Refrigerant pipes (split air conditioners, VRV)
Installation Instructions	Required minimum insulation thickness
1. Through an air-conditioned space	19mm
2. Through a non-air-conditioned space	19mm
3. Through a bathroom ceiling	25mm

Thermal Conductivity

Centrifugal Glass Wool λ = 0.031 + 0.00017 tm W/m.K

Flexible Foam Rubber λ = 0.03375 + 0.000125 tm W/m.K

Polyurethane λ = 0.0275 + 0.0009 tm W/m.K

Rigid Polyurethane Foam (Direct Burial) λ = 0.02 + 0.00014 tm W/m.K

Rock Wool or Mineral Wool λ = 0.0314 + 0.0002 tm W/m.K

tm - Average temperature of the insulation layer in °C, calculated as the average temperature of the heat and coolant in the pipe and the surrounding air.