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Table 1: Indicative thickness of insulation to control heat loss for non-domestic medium-temperature heating service areas
Outside diameter of pipe on which insulation thickness has been based (mm)	Thermal conductivity (W/m2K) at insulation mean temperature when used with a facing of low-emissivity (0.05 W/m2K)							Maximum permissible heat loss (W/m)
	Thickness of insulation (mm)
	0.025	0.03	0.035	0.04	0.045	0.05	0.055
17.2	11	15	20	26	34	44	56	13.34
21.3	14	18	25	32	42	54	69	13.56
26.9	17	24	31	41	53	67	85	13.83
33.7	21	28	37	48	62	78	98	14.39
42.4	24	32	41	52	66	83	103	15.66
48.3	25	33	42	53	67	83	102	16.67
60.3	27	36	46	57	71	87	106	18.25
76.1	30	39	49	60	74	89	107	20.42
88.9	31	40	51	62	76	91	108	22.09
114.3	34	43	54	65	79	93	110	25.31
139.7	36	46	57	68	82	96	112	28.23
168.3	38	48	59	70	83	98	113	31.61
219.1	40	50	61	72	85	98	113	37.66
273.0 and above	42	52	63	74	87	100	114	43.72
Notes
Figures apply to the case where the water temperature is 100°C and the ambient air temperature is 15°C. Heat loss relates to the specified thickness and temperature. The maximum permissible heat loss applies to all pipe materials (ie steel, copper, plastic and other). For an intermediate pipe diameter not listed in the table, compliance calculations shall use the nearest larger diameter listed. For pipes or vessels of diameter greater than 273 mm, the item shall be assumed to be 273 mm for calculation purposes. Source TIMSA Guidance for Achieving Compliance with Part L of the Building Regulations

Table 2: Thickness of insulation required to control heat transfer in cases of heating pipe and cooling duct
	Thermal conductivity of insulation product² (W/mK)	Minimum thickness of insulation product required³ (mm)	Supplied thickness of product (mm)
Medium-temperature 21.3 mm diameter heat pipe with a maximum allowable heat loss 13.56 W/m	0.036	26	30 (Crown Pipe Insulation)
Chilled and dual-purpose duct carrying air. Maximum allowable heat gain 6.42 W/m2	0.0032	50	50 (Crown Duct Slab Plus)
¹ From tables in Timsa HVAC guide
² From manufacturer’s product data
³ Calculated from Knauf Insulation HVAC calculation tool