Copper in Green BuildingsBeing “green” isn’t always the most economical option for residential and commercialbuildings, but it can help reduce overall operating expenses and costs in terms ofreduced repairs and maintenance in the long term, thus making initial capitalinvestment in these aging-friendly materials a wise decision. Few people realizethat buildings have the greatest impact on climate change -- more thantransportation and industry -- because they consume so much electricity and naturalgas, and theyre all powered by power plants that themselves produce carbonemissions. Copper can be found making an impact throughout any building.According to Tom Dietsche, LEED Program Manager, USGBC, “Green Buildingprojects that can earn LEED points include those that have incorporated recycledcontent materials, such as copper, which promotes sustainability and helps toreduce the impact of new material extraction on the environment."Copper is possibly the greenest commonly used architectural metal today. Copperplays an essential role in the modern building, from recycled cladding and roofingsystems, to high-tech plumbing and heating systems using tube and fittings whichare manufactured from recycled copper. Even the wire and cable systems andmonitoring equipment depend on upsized copper wire to maximize system efficiency,eliminate power quality issues, and play a key role in green power systems. Copperand copper alloys are also used in the manufacture of interior design fixtures anddecorative objects. Handles, door knobs and lock cylinders are current hardwareitems found in homes around the world. As the most frequently used processingmethods, copper sheeting, tubing and wiring produce most of the copper objectsaround us. Copper sheet is light in weight, easy to work and join, visuallyattractive and extremely durable. It resists attacks by air and moisture. Copperalloys, such as bronzes and brasses (Copper, alloyed with aluminium and zincprincipally) are also used in architectural design, offering a variety of colours andfinishes, combined with coppers exceptional characteristics.Copper is a key component of many energy-saving technologies. For example,passive solar water heating systems employ copper to capture and convertsunlight into heat. Copper heat exchangers efficiently transfer the thermal energyabsorbed by the solar collector to the home’s hot water system. Sunlight is abundant,renewable and, even where it is not readily available, can supplement a home’s hotwater needs virtually cost-free once a system is installed. Another option toconsider for home heating is a Direct Exchange (DX) geothermal system, whichuses a refrigerant directly circulating in underground copper tubing to extract ordisperse heat. By exploiting the earth’s constant temperature, DX systems efficientlyheat and cool homes and commercial buildings, reducing and in many caseseliminating the need for standard air conditioning and heating. Keep in mindthat even standard units benefit significantly as a result of the higher energy-efficiency performance they can derive from copper heat-exchange components.Builders can use copper to conserve energy through the installation of a heatexchanger for wastewater recovery. This type of heat exchanger typically has alarge-diameter copper pipe wrapped in thin-wall copper tubing. Warm wastewaterflowing through the larger pipe transfers its heat to the outer coil carrying the home’sdomestic water, which in turn reduces the amount of electricity or gas needed tomake hot water.Use of copper plumbing avoids the controversial use of polyvinyl chloride (PVC), apotential carcinogen according to the US Environmental Protection Agency. (US-
EPA). It is specified for use in most commercial plumbing, and is used extensively asa tubing material in HVAC systems. Copper used for plumbing tube; sheet productssuch as cladding, flashing and roofing applications; heating and cooling systems; andthe copper found in brass or bronze builders hardware and fixtures can be recycledover and over with no loss of its physical attributes.Another option for green plumbing systems is radiant heating that uses copper tocirculate water or a heat transfer fluid. Hot water recirculating systems that rely oncopper tubing for efficient fluid transfer are also gaining in popularity. Unlike moreconventional hydronic or forced-air heating methods, radiant heat systems radiateenergy directly to an area’s objects and its inhabitants. Because this is a moreefficient way to transfer heat, a building can achieve a level of comfort and warmthat a lower overall temperature, saving energy and reducing heating costs. Thesesystems not only increase energy efficiency, they help to conserve water aswell. The most efficient systems are designed to operate only when needed, soenergy is not required to circulate water all of the time. In addition, it offers severalattributes that make it ideal for fire sprinkler systems.The building industry has long valued the beauty, longevity and practicality ofcopper. It is one of the few architectural metals commonly used without theapplication of a coating or finish applied to retain and enhance its natural appeal andlong life. Its high ductility makes it easily formable--so it is easy to work with andideal for cladding complicated details and shapes. Copper is also naturallyresistant to weathering and decay, and can be alloyed with other commonlyavailable metals to increase its strength and performance characteristics, color, andtarnish resistance. Thus making it an important material for sustainable, greenbuilding projects.Soft temper copper is very malleable and best suited for applications like intricateornamental work. With the development of cold rolling, the gauge or thickness of thecopper could be reduced without compromising its durability and low maintenanceproperties--producing light weight, stronger copper product forms that maintain muchof the formability and ease of installation of soft temper for building systems whereintricate detail is not needed. Because of its excellent mix of strength and formability,cold rolled is the most common copper temper currently used in buildingconstruction. Copper’s long service life and low maintenance properties have lead toits application for a variety of building systems and types.Some of the worlds most distinguished architects are using copper for its supremecombination of technical and aesthetic properties. The Metropolis Museum ofScience in Amsterdam, designed by Renzo Piano, is clad in green pre-patinatedcopper. In Stockholm, the copper-roofed museum designed by Marianne Dahlbäckand Göran Månsson, winners of an architectural competition attracting 384 entries,houses the Vasa, the only intact seventeenth century ship in the world. Increasingly,copper and brass are the materials of choice for interior designers such as AndreaPonsi (The Copper House, 1990s) in creating original contemporary furniture.Copper facts for green buildingsLightweightCopper when used as a fully supported roof covering is half the weight (includingsubstrate) of lead and only a quarter of tiled roofs, with consequent savings insupporting structure and materials generally.
Low Thermal MovementWith a thermal expansion value 40% less than both zinc and lead, properly designedcopper roofs minimise movements due to thermal changes, avoiding deteriorationand failure. In addition, the high melting point of copper ensures that it will not “creep”or stretch as some other metals do.Indefinite LifeCopper roofs have been known to perform well for over 700 years and it is invariablysubstrates - not the copper itself - which eventually fail.No MaintenanceCopper does not require any decoration, cleaning or maintenance. It is thereforeparticularly suited for areas which are difficult or dangerous to access aftercompletion.DurableCopper exposed to the outside protects itself by developing a patina over time, whichcan reform if damaged, ensuring extreme durability and resistance to corrosion invirtually anyatmosphere. Unlike some other metals, copper does not suffer from undersidecorrosion.Cost-effectiveWith its indefinite life and unique visual characteristics, copper roofing is often foundon prestigious buildings and might be perceived as a “premium” material. However,recent independent research has shown that, because of light weight and otherbenefits, copper roofs are comparable with zinc, stainless steel, aluminium andeven some clay and concrete tiles when considering overall roofing costs (includingstructure). Copper roofing is considerably less expensive than lead, Welsh slate orhand made clay tiles. Using life cycle costings, the research also reveals copper as amore cost-effective material than virtually any other for roofs with a 30 year orgreater life, due to its durability, maintenance free nature and ultimate salvagevalue. With the growing interest in copper roofing by building designers, contractorsare becoming increasingly familiar with prefabrication, mechanised seaming andother cost saving techniques. The cost competitiveness of copper is resulting in itsuse on a much wider variety of building types than in the past - not just on prestigiousprojects. To maximize the low maintenance benefit of the cladding, copper canbe used for sun shading. The use of copper on the façade also contributessubstantially to minimizing the expected maintenance requirements of the building.Copper’s properties mean the cladding is essentially maintenance free, whichreduces the operating costs of the building. Beyond the financial rewards,environmental benefits include eliminating the need for chemical or artificialcoatings or finishes.Durability & LifespanCopper roofing and cladding exposed to the elements develop a protective patinaover time which can reform if damaged. This ensures extreme durability andresistance to corrosion in virtually any atmospheric conditions and, unlike someother roofing metals, copper does not suffer from underside corrosion. Consequently,it is invariably the supporting substrates or structure which eventually fails rather thanthe copper cladding itself and copper roofs have been known to perform well for over700 years. Similar empirical evidence cannot be provided for more recentlydeveloped cladding materials such as stainless steel, even though long life spans(e.g. 100 years) are claimed for them.
Copper’s patination process is complex, involving initial formation of copper oxideconversion films, gradually interspersed over a number of years with cupreous andcupric sulphide conversion films, and culminating with conversion of the sulphidefilms to the green copper sulphate patina.The rate of corrosion from the copper surface decreases with patination and isconsidered to average between 0.0001 and 0.0003mm per year. For a 0.6mm thicksheet, this equates to no more than 5% corrosion over 100 years. The lifespan ofcopper roofing and cladding can therefore be regarded conservatively as 200 years,subject to substrate and structure, and this is endorsed by experience. Naturally, thishas a significant effect upon comparative whole of life assessments in terms ofenergy consumption,CO2 generation and cost.Heat CaptureThe ability of the copper cladding to capture the heat of the sun in winter came asa pleasant surprise to the building’s operators. Based on what they learned,designers of the building have exploited this “solar wall strategy” in subsequentprojects.Embodied Energy & Co2An important, but often misused environmental indicator is the ‘embodied energy’ ofa material, which is the total energy consumed during every phase of each life cyclefrom cradle to grave. Estimates for the various roofing and cladding metals varywildly, partly because of a lack of current information but also because of basic errorssuch as: • Comparing energy per tonne rather than per m2 of material, thus misrepresenting thinner, lighter materials such as copper • Using inappropriate life span estimates (such as 70 years for copper compared with 100 years for stainless steel) resulting in additional theoretical “energy use” for unnecessary re-roofing • Ignoring current, more efficient recycling practices used in the copper industry. The following tables provide useful, up-to-date comparisons of embodied energy and carbon dioxide emissions for typical roofing and cladding metals, considered over ‘whole of life’ (or ‘End of Life’).Material thicknesses shown are typical for fully supported roofing techniques. Valuesare taken from a study performed by the Fraunhofer Institute with the participation ofPE Europe GMBH Life Cycle Engineering. (Source: German Ministry forEnvironmental Affairs, 2004). Copper Stainless Steel AluminiumThickness (mm) 0.6 0.4 0.7Life span (years) 200 100 100Embodied Energy(MJ/m2) 103.3 157.2 115.4An important criteria of copper is its low level of embodied energy. Copper is highlyrecyclable and durable and retains between 90-95% of its value relative to the cost ofnew copper.3 As a result of this characteristic, the majority of copper extractedthrough history is still in circulation today, used over and over in a variety ofapplications. With continuing concerns about global warming, embodied CO2emissions also provide an important indicator: for example, the BRE Environmental
Profiling System provides a weighting for CO2 eight times greater than that for SO2.The following estimates, from the same source as for those above, offer guidance Copper Stainless Steel AluminiumThickness (mm) 0.6 0.4 0.7CO2 equivalent emissions(kg/m2) 6.6 10.9 7.5Another problem in making assessments of this sort is that available information isinvariably dated. Production processes are improving all the time in terms ofefficiency and waste limitation. In addition, the latest construction techniques such asthe long strip method offer long life, complete roofing solutions with lower costs andembodied energy values which have yet to be properly assessed.CDM Regulations, health and safetyCopper is non-toxic and presents no risks with long term contact. Consequently, thelegislative controls and continuing programme of health monitoring needed for siteworkers and those handling other metals such as lead do not apply to copperworkers. The weight of copper needed to cover a given area is substantially less thanthat of lead, reducing lifting problems - particularly at high levels. Copper is thereforea safer alternative to lead for flashings and other weatherings - even on non-copperroofs. Copper maintains a consistent malleability and “feel” which makes manualworking entirely predictable. Indeed, metal roofing installers show a clear preferencetowards copper over other metals. It can be worked at all temperatures and, unlikemetals such as zinc, does not become brittle and break to form sharp edges in coldweather. Copper is ideally suited to mechanisation techniques, includingpreforming of trays and joints in safe locations and the use of automatic seamingmachines on roofs, minimising high level work (as recommended by the Health andSafety Executive).InnovationCopper Increases Efficiency of Solar Cells : In the past, it has been more expensiveto convert solar energy to electricity, as compared to other more readily availableenergy sources. But thanks to the joint effects of Siemens Solar GmbH in Munich,Germany (a joint venture of Siemens AG and Bayernwerk AG); Siemens SolarIndustries, a limited partnership in Camarillo, California; and two joint ventures,Siemens Showa Solar Ltd. In Singapore, and Showa Solar Energy K.K. in Tokyo,Japan; working together with the U.S. Department of Energys (DOE) Thin-filmPhotovoltaics Partnership Program, a new breakthrough could make solar powermore plentiful and inexpensive. This group of professionals have set about testingthe capabilities of a new thin-film photovoltaic module that is created by applying afine film of copper indium diselenide (CIS) to a glass backing - producing a semi-conductor. When the semi-conductor is exposed to sunlight, it actively convertssunlight into electricity - at a cost up to 10 times less than the crystalline silicon basedcells now on the market. This record setting one-foot by four-foot module wasdeveloped in collaboration with U.S. Governments National Renewable EnergyLaboratory (NREL). Record breaking efficiencies of more than 12 percent have beenconfirmed for this new thin-film module - Siemens Solar ST40 large-area copperindium diselenide (CIS) photovoltaic (PV) product.