Understanding BS 5422

These days, most building services specifications require systems to be insulated to BS 5422. This standard provides the recommended minimum thickness of insulation needed for elements such as pipe and ductwork on different systems. However, the required thickness of insulation will vary depending on the thermal performance of the product being fitted, and the operating parameters for the system. This means it is important to check you are applying the standard correctly, writes John O’Gorman, National Sales and Specification Manager, Kingspan Technical Insulation Ireland.

BS 5422 provides a range of tables with minimum insulation thicknesses for different systems and scenarios. To find the correct table, you’ll need to know certain information about the system, such as its operating temperature and pipe diameters.

Once you have the correct table, the other piece of information you’ll need is the thermal conductivity or lambda ( ) of the insulation material. The lower the lambda of an insulation material, the more effective it is at preventing heat loss. This means it may be possible to fit a slimmer thickness of insulation without compromising on thermal performance.

Conductivity varies

The thermal conductivity of insulation materials can vary a lot. For example, while mineral fibre lagging typically only achieves values of 0.033 W/mK or worse, Kingspan Kooltherm Pipe Insulation reaches aged thermal conductivities as low as 0.025 W/mK. As we’ll see, this can have a big impact on the thickness of insulation required.

All pipe insulation products should be supplied with clear information about their thermal conductivities. These will vary depending on the mean temperature of the insulation. To find the correct value for your application, add the operating temperature of the system to the ambient temperature and then divide this value by two.

In this example, we’ll look at a section of Table 15 (see below) which covers pipe insulation for non domestic heating services to control heat loss – low emissivity outer surfaces. In the left-column (in red), several standard pipework diameters are listed, while along the top (in green) are the expected operating temperatures separated into groups.

As these each cover a range of operating temperatures, a single standardised temperature is used within the calculation (listed in the row below). Once you’ve matched these up you can then select the appropriate lambda value from the fourth row (in blue). As you can see, the higher the lambda, the greater the thickness of insulation.

As the table only covers thermal conductivities in 0.005 WmK increments, the thermal conductivity for your chosen product may not be listed. Where this is the case, you can choose to round up to the nearest value. Alternatively, Kingspan offers pre-calculated tables within Kooltherm Pipe Insulation literature to ensure you can stay below the max heat loss value (shown in yellow) with the slimmest insulation thickness.

Contact: Kingspan Insulation. T: 042 975 4219; E: hvactechnical@kingspaninsulation.co.uk www.kingspantechnicalinsulation.ie

Indicative thickness of insulation for non-domestic heating services to control heat loss – low emisivity outer surfaces

Outside diameter Low emissivity surface fi nish ( = 0.05) of steel pipe on Low temperature heating services ( 95oC) Medium temperature heating services (96oC – 120oC) which insulation t = 75 t = 100 thickness has = 0.25 = 0.30 = 0.35 = 0.40 = 0.45 = 0.50 = 0.55 Max = 0.25 = 0.30 = 0.35 = 0.40 = 0.45 = 0.50 = 0.55 Max

been based Heat Loss Heat Loss

(mm) Thickness of insulation (mm) (W/m) Thickness of insulation (mm) (W/m)

17.2 12 17 22 30 39 51 66 8.9 11 15 20 26 34 44 56 13.34 21.3 14 20 26 35 46 59 75 9.28 14 18 25 32 42 54 69 13.56 26.9 16 22 29 38 49 62 78 10.06 17 24 31 41 53 67 85 13.83 33.7 18 24 31 40 51 64 79 11.07 21 28 37 48 62 78 98 14.39 42.4 20 26 33 42 52 65 79 12.3 24 32 41 52 66 83 103 15.66 48.3 21 27 35 44 55 67 82 12.94 25 33 42 53 67 83 102 16.67 60.3 23 29 37 46 56 68 82 14.45 27 36 46 57 71 87 106 18.25 76.1 24 31 39 48 58 70 83 16.35 30 39 49 60 74 89 107 20.42 88.9 25 32 40 49 59 70 82 17.91 31 40 51 62 76 91 108 22.09 114.3 27 34 42 51 61 71 83 20.77 34 43 54 65 79 93 110 25.31 139.7 28 35 43 52 61 71 82 23.71 36 46 57 68 82 96 112 28.23 168.3 29 37 44 53 62 72 82 26.89 38 48 59 70 83 98 113 31.61 219.1 30 38 45 54 62 72 82 32.54 40 50 61 72 85 98 113 37.66 273 31 38 46 54 62 71 80 38.83 42 52 63 74 87 100 114 43.72