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CPD 5: Environmental benefits of lead sheet

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This module considers the sustainability credentials of lead sheeting, as recently assessed by the BRE Green Guide. It is sponsored by the Lead Sheet Association

How to take this module

LSA

To take this module read the technical article below and click through to a multiple-choice questionnaire, once taken you will receive your results and if you successfully pass you will be issued automatically with a certificate to print for your records.

CPD

 

Introduction to rolled lead sheeting

Lead sheeting to BS EN 12588 is a versatile material used on a variety of buildings, from the flashings on domestic porches and cladding and roofing on modern commercial buildings, to the domes of heritage buildings and churches, mosques and synagogues around the world. According to the Lead Sheet Association, most of the lead sheet produced is used for flashings and weatherings, about 15% is used for restoration projects and about 15% is used for modern roof coverings and cladding systems, both as traditionally fixed and preformed panel systems. This CPD module will look at the environmental benefits of using lead sheet for roofing and cladding.

CPD

Environmental benefits of lead sheeting

Lead sheeting offers a number of environmental benefits. It is 100% recyclable and can be used repeatedly without a loss of performance. More than 95% of the lead used in the manufacture of lead sheeting is recycled. Lead also has a relatively low melting point of 327˚C, which means that less fuel is burned during its manufacture, reducing associated carbon emissions.

These factors have recently resulted in most standard lead roofing and vertical cladding installations receiving ratings of A or A+ in the BRE Green Guide to Specification. According to the BRE, when used in vertical cladding applications, lead has a carbon footprint of between 30 and 76kgCO2 per kg of material. When used on flat or sloping roof installations, this range falls to between 4 and 58kgCO2. This is considerably lower than similar installations using copper, zinc and stainless steel. There are few statistics for newer materials made from hydrocarbon products, but these are likely to have even higher carbon footprints.

Lead has also achieved good scores under the BRE’s Ecopoints assessment method. This measures the overall environmental impact of a particular product or process. The impacts considered include climate change, fossil fuel depletion, ozone depletion, freight transport, waste disposal and water extraction. A higher number of Ecopoints indicates a greater environmental impact - for example, the annual environmental impact caused by a typical UK citizen creates 100 Ecopoints.

According to the BRE, lead will generate between 0.5 and 0.66 Ecopoints, depending on the form of roof or cladding system adopted. Further details can be found in the BRE Green Guide to Specification.

In addition to these environmental benefits, a study by the Netherlands Organisation for Applied Scientific Research found that the concentration of lead in rainwater run-off has no public health or environmental impact.

Use of lead sheet in roofing and cladding

A number of factors make lead sheeting particularly suitable for roofing and cladding applications. These are outlined below:

  • It is long-lasting. Most lead roof products have a lifespan of at least 60 years, and often longer
  • It is malleable, which makes it easy to install, but rigid enough to avoid wind-lift
  • It is weather-tight
  • It requires a low level of maintenance
  • It can be installed in most weather conditions.

The Lead Sheet Association recommends the use of rolled lead sheeting in thicknesses between codes 5 and 8 for the main types of roofing and cladding. This is shown in the table below:

Type of application/codeSheltered/moderate exposureSevere exposureHistoric or listed building
Flat roof5, 66, 77, 8
Pitched roof4, 5, 66, 77, 8
Vertical cladding4, 55, 66, 7
Dormer roof4, 55, 66, 7, 8



This is based on the BS EN 12588 codes for lead sheet thickness, as shown in the table below.

 Weight per m2 (kg)Thickness (mm)
Code 314.971.32
Code 420.411.80
Code 525.402.24
Code 630.052.65
Code 735.723.15
Code 840.263.55

 

Lead sheeting in the BRE Green Guide to Specification

The BRE considered a variety of code 5 lead sheet applications and compared their environmental performance (in terms of carbon footprint) with non-lead specifications. This showed, for example, that 100% recycled lead sheet on plywood compared favourably with glass reinforced plastic (GRP) cladding for external wall applications. A specification comprising “code 5 100% recycled lead sheet on plywood (temperate EN636-2), timber battens, breather membrane, no sheathing, insulation, light steel frame, plasterboard on battens, paint” achieved an A+ rating and 0.48 Ecopoints, producing 43kg of CO2 equivalent. A specification of “comparable GRP cladding, aluminium fixing rails, insulation, light steel frame, vapour control layer, plasterboard on battens, paint” produced 110kg and earned only an A rating.

The BRE also found that when used on external walls, code 5 lead sheet on plywood consistently had a smaller carbon footprint than comparable specifications in copper or coated aluminium.

The carbon footprints of A and A+ rated lead-sheeting applications range from 30kg of CO2 (for a timber-frame option with insulation) to 76kg (for a specification with a medium-dense solid-block outer wall and aircrete inner wall). By contrast, comparable A and A+ rated copper options have footprints of between 46 and 120kg and aluminium equivalents range between 70 and 110kg. Applications of other products laid on softwood boarding tend to have a carbon footprint of between 37 and 45kg.

In terms of roofing, the BRE found that applications based on lead sheeting and timber often had considerably lower carbon footprints than comparable options using plastic single-ply waterproofing membranes. For example, a specification of “timber joists, OSB/3 decking, vapour control layer, insulation, softwood timber underboarding, polyester underlay, code 5 100% recycled lead sheet” produced 4.5kg of CO2 equivalent. Meanwhile, a comparable PVC system with “timber joists, OSB/3 decking, vapour control layer, insulation, PVC single-ply waterproofing membrane” was found to produce 31kg.

The carbon footprint of lead sheet roofing solutions also compared favourably to A-rated specifications using locally sourced slates and standing seam copper. For example, specifying “2 x 15mm OSB with 112mm rigid urethane insulation, breather membrane, counter battens, battens, plywood (temperate EN 636-2), building paper, code 5 100% recycled lead sheet” produced 42kg of CO2 equivalent, while replacing the plywood, paper and lead sheet with UK-produced slates increased this to 51kg. Meanwhile, a specification of “galvanised steel rafters and joists with insulation, battens, breather membrane, plywood (temperate EN 636-2), building paper, code 5 100% recycled lead sheet” produced 58kg, while an equivalent with a standing seam copper roof produced 72kg.

The Lead Sheet Association will be running a seminar on “Lead - the ‘new’ eco material” at Ecobuild.
For more information visit www.ecobuild.co.uk/profiles

How to take this module

To take this module read the technical article below and click through to a multiple-choice questionnaire, once taken you will receive your results and if you successfully pass you will be issued automatically with a certificate to print for your records.

CPD

 

 

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Readers' comments (1)

  • This is interesting.
    The Swiss enviromental standard of "Minergie-Eco" excludes lead from the list of permitted materials.
    This applies in particular to roof sheeting.
    If one wants to use it, a metal filter has to be installed in the rainwater drainage system.

    Unsuitable or offensive? Report this comment

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