October 2010

An introduction to Part L insulating pipes and ducts

Straight talking solutions

The insulation of pipes and ducts is essential to minimise heat losses for heated systems and heat gains for cooled systems. For cooled systems, it is also important to ensure that the risk of condensation is adequately controlled. Guidance on controlling condensation is also provided in this Part L Rockwool guide.

ADL1A and ADL1B DwellingsThe Domestic Building Services Compliance Guide 2010 provides guidance on the means of complying with requirements for space heating systems and hot water systems in new and existing domestic buildings.

ADL2A and ADL2B Buildings other than dwellingsThe Non-Domestic Building Services Compliance Guide 2010 provides guidance on the means of complying with requirements for space heating systems, hot water systems and cooling & ventilation systems in new and existing non-domestic buildings.

The new Approved Documents ADL1A, ADL1B, ADL2A and ADL2B rely on second-tier documents published by the department for Communities and Local Government (CLG) to provide detailed information on the minimum provisions necessary to comply with the requirements of the Regulations.

The Part L second-tier documents for pipe and duct insulation

This document is a support document to our publication an introduction to Part L 2010 which is available from our website at www.rockwool.co.uk/partL

2 | An introduction to Part L insulating pipes and ducts

Domestic heating compliance guideCompliance with approved documents L1A: new dwellings and L1B: existing dwellings

Approved Documents ADL1A and ADL1B rely on second tier documents to provide detailed information on the minimum provisions necessary to comply with the requirements of the Regulations.

The Domestic Building Services Compliance Guide (2010) is a second tier document providing guidance on the means of complying with the requirements for space heating systems and hot water systems.

Minimum provisions for insulation of pipes The minimum provisions shown below for the insulation of pipes are repeated in the Domestic Domestic Building Services Compliance Guide (2010) for fuel types and heating systems as follows; Gas-firedprimaryandsecondary

space heating and hot water Oil-firedprimaryandsecondary

space heating and hot water Electricprimaryandsecondary

space heating and hot water Solid-fuelprimaryandsecondary

space heating and hot water Communityheating Solarwaterheating

Minimum provisionIn new systems pipes should, in the following cases, be insulated with insulation complying with the requirements of the Domestic Building Services Compliance Guide (2010) (in line with the maximum permissible heat loss indicated in the Supplementary Information column), and labelled accordingly: Primarycirculationpipesforheatingandhotwater

circuits should be insulated wherever they pass outside the heated living space or through voids which communicate with and are ventilated from unheated spaces

Primarycirculationpipesfordomestichotwatercircuits should be insulated throughout their length, subject only to practical constraints imposed by the need to penetrate joists and other structural elements

Allpipesconnectedtohotwaterstoragevessels,including the vent pipe, should be insulated for at least 1m from their points of connection to the cylinder (or they should be insulated up to the point where they become concealed)

Ifsecondarycirculationisused,allpipeskepthotby that circulation should be insulated

For replacement systems, whenever a boiler or hot water storage vessel is replaced in an existing system, any pipes (in the situations above) that are exposed as part of the work or are otherwise accessible should be insulated with insulation complying with the requirements of the Domestic Building Services Compliance Guide (2010)(in line with the maximum permissible heat loss indicated in the Supplementary Information column), and labelled accordingly or to some lesser standard where practical constraints dictate.

Supplementary informationInsulation for pipework in unheated areasExtraprovisionmayneedtobemadetoprotectcentral heating and hot water pipework in unheated areas against freezing. Further guidance is available in: BS5422:2009Methodforspecifyingthermal

insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperaturerangeof40Cto+700C

BREReportNo262Thermalinsulation:avoidingrisks, 2002 edition

Where insulation is labelled as complying with the Domestic Building Services Compliance Guide (2010) it must not exceed the following heat loss levels:

Domestic Heating compliance

Pipe Diameter (OD)mm

Table1:Maximum permissible heat loss* (W/m)

(Thickness of Rockwool Rocklap H&V Pipe Section)

10 mm 7.23(n/a)

12 mm 7.35(n/a)

15 mm 7.89(20mm)

22 mm 9.12(20mm)

28mm 10.07(20mm)

35mm 11.08(20mm)

42mm 12.19(20mm)

54mm 14.12(20mm)

*In assessing the thickness of insulation required to meet the provision, standardised conditions should be used in all compliance calculations based in this instance onahorizontalpipeat60Cinstillairat15C.Furtherassistance in converting these heat loss limits to levels (thickness) of insulation for specific thermal conductivities isfoundintheTIMSAHVACGuidanceforachievingcompliance with Part L of the Building Regulations.

Due to rounding up to the nearest commercially available thickness, the thermal performance required will be met or exceeded.

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Non-domestic compliance guide

Non-domestic heating, cooling and ventilation compliance guideCompliance with approved documents L2A: New Buildings other than Dwellings and L2B:ExistingBuildings other than Dwellings

Pipework and duct insulation Approved Documents ADL2A and ADL2B (2010) rely on second-tier documents to provide detailed information on the minimum provisions necessary to comply with the requirements of the Regulations.

The Non-Domestic Building Services Compliance Guide 2010 (the Non-domestic HVAC Guide) is a second-tier document providing guidance on the means of complying with the requirements for space heating systems, hot water systems, cooling and ventilation systems.

Section 11 of the Non-domestic Guide outlines the minimum provisions needed to comply with ADL2A and ADL2B when insulating pipes and ducts serving space heating, hot water and cooling systems in new-build and in existing buildings.

The insulation of pipes and ducts is essential to minimise heat losses for heated systems and heat gains for cooled systems. For cooled systems, it is also important to ensure that the risk of condensation is adequately controlled. Although not within the scope of the Non-Domestic Guide, guidance on controlling condensation is also provided in this Rockwool Guide.a direct hot water pipes and low, medium & high

temperature heating pipes b cooled water supply pipesc heated air ducts, cooled air ducts and dual-

purpose heated & cooled air ductsd condensation control

4 | An introduction to Part L insulating pipes and ducts

a. Direct hot water and heating pipeworkPipework serving space heating and hot water systems should be insulated in all areas outside of the heated building envelope. In addition, pipes should be insulated in all voids within the building envelope and within spaces that will normally be heated if there is a possibility that those spaces might be maintained at temperatures different to those maintained in other zones. The guiding principles are that control should be maximised and that heat loss from un-insulated pipes should only be permitted where the heat can be demonstrated as always useful. In order to demonstrate compliance the maximum permissible heat losses for different pipe sizes and temperatures, as given in the table below should not be exceeded.

Table 2: Maximum Permissible Heat Loss (W/m) (Thickness of Rockwool Rocklap H&V Pipe Section)

Pipe Outside Diameter (mm)

Hot Water1 Low Temp. Heating2

95C

Medium Temp Heating3

96C 120C

High Temp Heating4

121C 150C

17.2 6.60 (25mm) 8.90(25mm) 13.34(25mm) 17.92(25mm)

21.3 7.13(25mm) 9.28(30mm) 13.56(30mm) 18.32(30mm)

26.9 7.83(30mm) 10.06 (35mm) 13.83(40mm) 18.70(40mm)

33.7 8.62(30mm) 11.07(35mm) 14.39(45mm) 19.02(50mm)

42.4 9.72(30mm) 12.30(35mm) 15.66 (50mm) 19.25(60mm)

48.3 10.21 (35mm) 12.94(40mm) 16.67(50mm) 20.17(70mm)

60.3 11.57(35mm) 14.45(40mm) 18.25(60mm) 21.96(70mm)

76.1 13.09(35mm) 16.35(45mm) 20.42(60mm) 24.21(80mm)

88.9 14.58(35mm) 17.91(45mm) 22.09(60mm) 25.99(80mm)

114.3 17.20(40mm) 20.77(45mm) 25.31(70mm) 29.32(80mm)

139.7 19.65(40mm) 23.71(50mm) 28.23(70mm) 32.47(90mm)

168.3 22.31(40mm) 26.89(50mm) 31.61(70mm) 36.04(90mm)

219.1 27.52(40mm) 32.54(50mm) 37.66(70mm) 42.16(90mm)

273.0&above 32.40(40mm) 38.83(50mm) 43.72(80mm) 48.48(100mm)

NOTES1,2,3,4Toensurecompliancewithmaximumpermissibleheatlosscriteria,proposedinsulationthicknessesshouldbecalculatedaccordingtoBSENISO12241usingstandardizedassumptions: 1Horizontalpipeat60Cinstillairat15C 2Horizontalpipeat75Cinstillairat15C 3Horizontalpipeat100Cinstillairat15C 4Horizontalpipeat125Cinstillairat15CDue to rounding up to the nearest commercially available thickness, the thermal performance required will be met or exceeded.

Non-domestic (continued)

Maximum permissible heat loss (W/m) for direct hot water and heating pipes. ReferenceTable41Section11BuildingServicesComplianceGuide(2010)

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Non-domestic (continued)

b. Cooled pipeworkCooled pipework should be insulated along its whole length in order to provide the necessary means of limiting heat gain. Control should be maximised and heat gain to uninsulated pipes should only be permitted where the proportion of the cooling load relating to distribution pipework is proven to be less than 5% of total load. In order to demonstrate compliance, the maximum permissible heat gain for different pipe sizes and temperatures, as given in the table below, should not be exceeded.

Maximum permissible heat gain for cooled water supplies.ReferenceTable42Section11BuildingServicesComplianceGuide(2010)

Table 3: Maximum Permissible Heat Gain (W/m) (Thickness of Rockwool Rocklap H&V Pipe Section)

Pipe Outside Diameter (mm)

>105Temperature of contents

(C)4.9 to 10.060 to 4.97

17.2 2.48 (20mm) 2.97(20mm) 3.47(20mm)

21.3 2.72(20mm) 3.27(20mm) 3.81(25mm)

26.9 3.05(20mm) 3.58(20mm) 4.18(25mm)

33.7 3.41(20mm) 4.01(25mm) 4.60(25mm)

42.4 3.86(20mm) 4.53(25mm) 5.11 (30mm)

48.3 4.11(20mm) 4.82(25mm) 5.45(30mm)

60.3 4.78(20mm) 5.48(25mm) 6.17(30mm)

76.1 5.51 (25mm) 6.30(25mm) 6.70(30mm)

88.9 6.17(25mm) 6.90(30mm) 7.77(30mm)

114.3 7.28(25mm) 8.31(30mm) 9.15(35mm)

139.7 8.52(25mm) 9.49(30mm) 10.45(35mm)

168.3 9.89(25mm) 10.97(30mm) 11.86(35mm)

219.1 12.27(25mm) 13.57(30mm) 14.61(35mm)

273.0&above 14.74(25mm) 16.28(30mm) 17.48(35mm)

NOTESThe insulation thicknesses shown are calculated specifically against the criteria noted in this table.

The insulation thicknesses shown are not sufficient to prevent condensation on low emissivity surfaces applied to insulatedpipeslocatedin25C,80%relativehumidityambientairasdescribedinBS5422.Additionalguidanceonthe control of condensation is provided in Table 5 of this Rockwool Guide.

5,6,7 To ensure compliance with maximum permissible heat gain criteria, proposed insulation thicknesses should be calculatedaccordingtoBSENISO12241usingstandardizedassumptions: 5Horizontalpipeat10Cinstillairat25C 6Horizontalpipeat5Cinstillairat25C 7Horizontalpipeat0Cinstillairat25C

Due to rounding up to the nearest commercially available thickness, the thermal performance required will be met or exceeded.

6 | An introduction to Part L insulating pipes and ducts

c. Hot and Cooled DuctingDucting should be insulated along its whole length in order to provide the necessary means of limiting heat gains and/or heat losses from ducts. Where ducting may be used for both heating and cooling duties at different periods during its lifecycle, the provisions for chilled ducting should be adopted, since these are the most onerous. The table below indicates the maximum heat gain/loss per unit area required to meet these provisions (heat gains are shown as negative values). As with pipes, additional insulation may be required to provide adequate condensation control. Further details regarding these specific requirementsaregivenintheTIMSAHVACGuide.

Table 4: Maximum Permissible Heat Gain/Loss (W/m2) (Thickness of Rockwool Ductwrap)

Heated Duct8 Dual Purpose9 Cooled Duct10

16.34(40mm) -6.45 (50mm) -6.45 (50mm)

NOTESThicknesses given are calculated specifically against the criteria noted in the table. Adopting these thicknesses may not necessarily satisfy other design requirements such as control of condensation. Additional guidance on the control of condensation is provided in Table 5 of this Rockwool Guide.

8,910 To ensure compliance with maximum permissible heat transfer criteria, proposed insulation thicknesses should becalculatedaccordingtoBSENISO12241usingstandardizedassumptions: 8Horizontalductat35C,with600mmverticalsidewallinstillairat15C 9Horizontalductat13C,with600mmverticalsidewallinstillairat25C 10Horizontalductat13C,with600mmverticalsidewallinstillairat25C

Due to rounding up to the nearest commercially available thickness, the thermal performance required will be met or exceeded.

Non-domestic (continued)

Maximum permissible heat gain/loss for insulated ducts used to carry cooled air (including those heated ducts used periodically for cooled air).ReferenceTable43Section11BuildingServicesCompliance Guide (2010)

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d. Condensation Control: Chilled and cold water pipes

Table: 5 Condensation Control

Outsidediameterofsteelpipe on which insulation has been based (mm)

Temperatureofcontents(C)

+10 +5 0

ThicknessofROCKWOOLRocklapH&VPipeSection(mm)

17.2

20

25 3021.3

26.9

3035

33.7

42.4

2540

48.3

3560.345

76.1

30

88.9

40 50101.6

114.3

139.745

60168.3

35219.1

50244.5

70273.0

40323.9

60

355.6

406.4

80

457.0

45508.0

610.070

Flat 50

NOTE:Thicknessesgivenarecalculatedspecificallyagainstthecriterianotedinthetable.Adoptingthese thicknesses may not necessarily satisfy other design requirements.

ReferenceTable8(BS5422:2001)Minimuminsulationthicknessforchilledandcoldwatersuppliestopreventcondensationonalowemissivityoutersurface(0.05)withanambienttemperatureof+25Candarelativehumidityof80%

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