Rainwater goods
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Aluminium |
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Cast Iron & Steel |
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Copper |
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Zinc |
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PVC |
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Glass Reinforced Polyester (GRP) |
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Wood |
Selecting the rainwater goods material with the least environmental impact is fraught with 'ifs and buts':
• In light of production processes which use large amounts of energy, metals look a doubtful prospect. But on closer examination of output, it is possible to see an industry that makes increasingly best use of recycled content - so possibly mitigating the impact of producing virgin (or 'primary') iron, steel, aluminium and copper. In considering the specification of metal rainwater goods, we would urge designers to examine the product manufacturer's material sourcing policy: 'Where does the metal come from? ' 'What kind of energy is used in the production process?' and 'How much of the product consists of recycled material?'
• Of the plastics alternatives, both GRP and PVC, are materials that depend on petrochemicals. GRP is probably the better choice because of its lesser dependence on oil; whilst PVC is a hard call for the many who believe that its production and disposal processes are potentially dangerous. Because both sides of the PVC debate are vociferous and prone to mis-lead, we would recommend designers review the evidence with a critical eye.
• Our own favourite is wood, the oldest form of guttering - common use of which, sadly, is fading from memory. Sourcing timber guttering has become notoriously difficult, but we would encourage specifiers to make the extra effort where possible and help in restouring this once traditional material to the designer's palette of materials. (A short list of suppliers / installers is provided at the foot of the page)
Aluminium
Embodied energy
• Of all the common metals used in construction, aluminium is noted for its very high level of embodied energy resulting from the smelting of its raw material, bauxite.
• There is an exception: though most bauxite is smelted using electricity generated by fossil fuels, a significant quantity of aluminium is produced using hydro-electricity. This is particularly true of aluminium produced in Norway, where nearly all electricity is derived from hydro.
• Though the use of hydro-electricity significantly reduces the amount of embodied energy, it does not eliminate it – this is because virgin aluminium uses coke as a raw material in the production of carbon anodes.
• The specifier should check with the manufacturer the nature of the energy used in production.
• Cast virgin: 222.5 MJ/kg (1)
• Cast recycled: 24.5 MJ/kg (1)
Recycled content
• Aluminium products contain, on average, 33% recycled aluminium. Quantities vary however and some products might be distinguished by their higher-than-average recycled content. When specifying, it is safe to assume that the product will contain an element of recycled aluminium - but the percentage should be checked with the manufacturer.
Design Life
40 - 60 years (2)
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Recyclable |
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Durable |
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Material efficiency realised through thin sections |
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Lightweight |
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Products can include high levels of recycled material |
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High embodied energy (but see above) |
Cast iron & steel
Pollution
• Coke production, an essential element of most iron and steel production, is a major source of VOCs and carbon monoxide emissions. Waste water from coke making has high contaminant levels, requiring extensive removal and treatment before disposal. Though emissions from iron and steel production have been much reduced through controls and technology, the environmental impact is still significant.
• Blast furnace iron making generates large quantities of sulphur and nitrogen oxides and carbon monoxide.
• Compared with the West, the environmental impact of steel and iron produced in China is relatively un-regulated. Though the situation is improving, the world’s largest producer remains a subject of concern.
• 95% of the cast iron manufactured is used in the production of steel. Steel is formed by treating molten iron with intense heat and alloying with carbon. The extra process increases embodied energy and releases further CO2 as well as dust, cadmium and fluorine compounds
Recycled content
• Much of the environmental impact of iron and steel production can be mitigated by the use of recycled material.
• Typically, cast iron rainwater goods can include around 70 – 75% recycled content.
• Worldwide, around 42% of the annual steel production is made of scrap. Using recycled steel uses approximately 30% of the energy associated with producing virgin steel. Steel rainwater goods can be expected to have a recycled content of about 70%.
Embodied energy
Iron:
• Cast iron: 25 MJ/kg (including and unknown % of recycled content) (1)
Steel:
• Steel pipe: 34.4 MJ/kg
• Stainless steel: 56.7 MJ/kg
• Galvanised steel: 39.0 7 MJ/kg
(figures assume 42.7% recycled content) (1)
Design Life
60 + years (2)
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Recyclable |
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Durable |
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Products can include high levels of recycled material |
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Iron is particularly resistant to damage |
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Extraction can lead to considerable landscape degradation |
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High levels of waste are associated with iron & steel production |
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High embodied energy involved in production |
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High embodied energy associated with import transportation |
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Iron needs regular painting |
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Steel needs painting, galvanising or other coatings |
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High levels of pollution including dioxins |
Copper
• Copper is a popular choice for rainwater goods in Europe. Its main attraction is its resistance to corrosion. Copper naturally oxidizes to a verdigris patina over a period of time (though this process can be artificially stimulated).
• Copper is a very limited resource. Optimists expect 60 years but some think it more like 25 years before supplies are exhausted.
• Historically copper was smelted, but modern production involves dissolving ore in sulphuric acid, then extracting pure copper through electrolysis.
• Copper can be toxic in sufficient concentrations. Combining copper rainwater goods with harvested drinking water is not advised.
Embodied energy
• General copper: 40 - 55 MJ/kg (assumes a recycled content of 46%)
• Recycled copper from high-grade scrap: 17.5 MJ/kg (1)
Design Life
60 + years (2)
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Recyclable |
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Durable |
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Products can include high levels of recycled material |
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Corrosion resistant |
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Very limited natural resource |
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High embodied energy |
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Toxic in high concentrations |
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Expensive |
Zinc
• Zinc reserves are extremely restricted. Zinc should be specified only where substitutes are not possible.
PVC (Poly Vinyl Chloride)
• PVC is manufactured as follows:
1 Chlorine is extracted from sea salt via electrolysis, and ethylene is derived from hydrocarbon raw materials. These are reacted to produce ethylene dichloride
2 Ethylene is combined with chlorine and oxygen to produce vinyl chloride monomer and water.
3 PVC is made by ' addition polymerisation.' This reaction opens the double bonds in the vinyl chloride monomer (VCM) allowing neighbouring molecules to join together creating long chain molecules.
• There continues debate about the safety of PVC.
Embodied energy
PVC pipe: 67.5 MJ/kg (1)
Design Life
20 - 30 years (2)
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Low maintenance |
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Cheap |
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Easy to install |
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Lightweight |
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Corrosion resistant |
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Recyclable |
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Concerns over the safety of PVC manufacture and disposal |
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High embodied energy |
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Petrochemical content - non-renewable resource, emissions associated with extraction & refining |
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Vulnerable to damage |
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Colour fading |
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Prone to leak at joints |
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Short life expectancy |
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Very little PVC is recycled |
GRP (Glass Reinforced Polyester)
• GRP is a ‘Thermoset Composite’ composed of polyester as the thermosetting polymeric matrix reinforced by fine fibres made from glass.
• The glass fibres, which account for 30% of the content of GRP, are made from sand, soda ash and limestone melted at high temperatures.
• Polyester is a petrochemical product
Embodied energy
100 MJ/kg (1)
Design Life
30 + years (2)
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Instantaneous hot water |
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High pressure hot water |
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Unsuitable for anything other than small homes |
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Unsuitable for low pressure supplies |
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Ancillary water heating (eg solar) requires extra storage and compatibility |
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Poor flow rate for baths. |
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Unsuitable for anything other than small homes |
Wood
• Wood is the oldest form of guttering. Popular until the 20th century, wood was replaced by cheaper plastic and metal alternatives.
• Wood guttering has the lowest environmental impact.
• To ensure durability, correct choice of wood is vital. Suitable species include Scots pine, Pitch pine, Sweet chestnut and Elm.
• Maintenance includes repainting of the outside and re-oiling of the inside (if no lining) on a regular basis.
• Wood performs best when un-painted. Painting increases drying time after rain.
• Durability can be increased by lining the gutter with single-ply roof covering, bitumen or specialist wood oil.
Embodied energy
General timber: 8.5 MJ/kg (1)
Design Life
70 + years if maintained correctly (2)
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Durable if maintained correctly |
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Negligible environmental impact + timber sequestered carbon dioxide |
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Without maintenance, wood gutters can rot, split and crack |
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Requires expert installation |
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Relatively expensive |
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Very few manufacturing sources (though some branches of Jewsons hold stocks) |
References
1 Inventory of Carbon & Energy (ICE) - Version 1.6a - Hammond & Jones, Univ Bath
2 Building Life Plans
Suppliers of wooden guttering
• Kinsley Timber, Pontefract, W. Yorks, 01977 611369
• Bennetts Timber, Grimsby, Lincs., 01472 350151, sales@bennettstimber.co.uk
• High Tech Roofing N/W, Salford, Lancs., 07729 811594, hightechroofing2004@hotmail.co.uk
• ST Building and Roofing, Sheffield, 0114 265 2055, stbuilders@btinternet.com
• A1 Gutterclean, Sheffield, 0114 268 2894, enquiries@a1gutterclean.co.uk
• Lancaster Woodcraft, Lancaster, 01524 771700, info@lancasterwoodcraft.co.uk
• Sheffield Roofline, 0114 230 3177, www.sheffield-roofline.com
Downloads
• GRP composites - Canadian Building Digest, 1979 (http://irc.nrc-cnrc.gc.ca/pubs/cbd/cbd205_e.html)
Further information
• Copper Development Association (www.copperinfo.co.uk)
• UK Steel (www.eef.org.uk/uksteel/default.htm)
• British Stainless Steel Association (www.bssa.org.uk)
• International Aluminium Institute (www.world-aluminium.org)
Rainwater drainage products on GreenSpec
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