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Doug Smeath is the Consumer Web Site Marketing Manager at the US Green Building Council

The contribution of buildings and the construction industry to climate change is often overlooked yet the industry is estimated to be responsible for up to 40 per cent of global energy use. With better buildings life cycle planning and the use of low carbon materials for construction, the amount of carbon dioxide emitted from the industry could be dramatically reduced.

In the global effort to combat climate change, the contributions of the built environment to the problem is often overlooked. Yet in the United States, for example, buildings are responsible for 39 per cent of the nation's carbon dioxide emissions - more than either transportation or industry. In fact, commercial and residential buildings use more than 70 per cent of the total electricity used in the US. And those totals don't even take into account buildings' ‘embodied' energy, ie the energy used to manufacture and transport the materials used to build them.

The picture is similar elsewhere in the world. The International Energy Agency estimated in 2005 that buildings account for 30 to 40 per cent of the world's energy use, a number that varies greatly depending on a country's climate and economy. In Europe, for example, buildings use about 40 to 45 per cent of the total energy consumed.

Given these figures, it is clear buildings significantly contribute to the climate change problem and so must be central part to a solution. If half of all new commercial buildings in the United States were built to use 50 per cent less energy, the amount of carbon dioxide emitted during a building's operations would reduce by more than six million tonnes. This is the equivalent of taking more than one million cars off the road every year. Minimising buildings' negative impact on the environment is a challenge facing professionals in the building, construction, design, real estate and other. The potential for solutions is only limited by the creativity and dedication of those professionals, each working to identify the most effective ways to address a particular building's needs based on its type, the climate and economy of where it is located, and social conditions among other variables.

The LEED Green Building Rating System

In 2000, the US Green Building Council launched the Leadership in Energy and Environmental Design (LEED®) Green Building Rating System as a tool to help build energy efficient, resource-friendly and healthier structures. The average LEED certified building uses 32 per cent less electricity and results in 350 tonnes less of carbon dioxide emissions annually.

The LEED Green Building Rating System is a point based system with building projects earning points or credits for satisfying specific green building criteria. Projects earn credits in categories including:
• Sustainable Sites.
• Water Efficiency; Materials & Resources.
• Energy & Atmosphere.
• Indoor Environmental Quality.
The number of points a project earns determines the level of LEED certification: Certified, Silver, Gold or Platinum.

Energy use

The greatest impact buildings have on climate change is through operational energy use. The most effective way to reduce that impact, therefore, is to reduce the amount of energy it takes to run a building during its life. The best strategies depend on a building's specific circumstances. Homes, for example, are especially well suited to make use of ‘passive' energy, ie heating, cooling, ventilation and other systems that rely on a building's directional orientation, well planned windows and glazing, and natural air flow.

But there are some energy saving methods all buildings should make use of. Chief among them is a tight, well insulated thermal envelope. A building that allows heat to seep in or out of it is not efficient and will waste energy on heating and cooling. A good building envelope makes use of efficient, sustainable insulation between walls and eliminates thermal bridges. A tight envelope is an especially important consideration in planning windows, the area of most heat transfer in a majority of buildings. Windows should be carefully chosen for their climate; clear glass lets in extra sunlight and is good for cooler climates, while more shading and darker glazing is more appropriate for warmer climates. Windows can also be designed to maximise natural daylight - a more energy efficient lighting strategy that also brings a host of physical and psychological health benefits, as long as it doesn't unnecessarily increase cooling costs.

Further energy savings can be achieved through smart appliance and fixture choices. In the United States, Energy Star rated appliances have been recognised for their efficiency and should be considered whenever possible. Lighting comes in a range of efficiency options, with light-emitting diodes among the most efficient. Compact fluorescent bulbs are more flexible and affordable, if less efficient, than LEDs, but they still beat conventional incandescent bulbs.

A building's energy supply also plays a big role in its contribution to climate change. Building planners should consider whether solar power is a viable option, either for water heating or power generation through photovoltaic cells. Wind turbines are also becoming more and more available and can help a building generate some or, in some cases, all of its own power. When alternative power sources are not realistic for a specific building, building operators should explore buying renewable energy from utility providers which is now a service most utilities offer.

Water use

Through changing precipitation patterns, climate change will put additional strain on global water supplies. The embodied energy of water is also a major contributing factor to climate change. Strategies such as rainwater harvesting, waterless urinals, aerators on faucets, use of non drinkable water for irrigation and installing timers on faucets are all effective ways to reduce water consumption. Encouraging reductions in the amount of water that needs to be conveyed to, and treated by, municipal wastewater treatment facilities reduces pumping and process energy required by systems. Additionally, onsite treatment of storm water minimises energy use by municipal treatment systems.

Materials and resources

Much of a building's energy use is represented by its ‘embodied energy', ie the amount of energy it takes to manufacture and transport the materials used in its construction. Building materials such as aluminum, cement and steel require a lot of energy to produce. The energy embodied in a single building's envelope is as much as eight to 10 times the annual energy used to heat and cool the building, according to the UN Environment Programme.

Selecting materials with low embodied energy - glulam beams instead of aluminum, for example - can help reduce a building's embodied energy. Another important strategy is the selection of locally sourced materials and products, minimising the fuel involved in their transportation. And many building materials are available as recycled content. Building sites can use recycled concrete and masonry from demolished buildings as fill, for example, and new masonry can make use of recycled content. Designers can also look to more creative reuse options, salvaging discarded goods and reusing them for new and interesting purposes; old glass bottles made into lamps or construction waste used for furniture among the countless possibilities. Such reuse helps reduce the energy used to create new goods and also cuts down on landfill waste.

Building materials should add to a building's durability and future recyclability. A building can make every effort to use materials with low embodied energy and high recycled content, but if they are poorly made and won't last for a few decades, they will only lead to a future demand for new materials and result in unnecessary waste.

Transportation and site selection

The axiom that ‘location, location, location' is key to good real estate applies to buildings' sustainability as well. Buildings that help people make sustainable choices in transportation go a long way toward reducing carbon emissions.

The strategies for achieving this goal are many and depend on a building's use and the availability of infrastructure. Where public transportation is available, buildings should be sited to be as accessible to that transit as possible. Walkability and high density are also key in designing and planning buildings, planned developments and neighborhoods. Mixed-use developments that combine residential, commercial, office, social, educational and other components reduce the need to travel long distances for daily errands. Offices can encourage alternative transportation by providing bicycle racks and showers for employees who bike to work.

Local climate

In most urban areas, the ‘heat island' effect acts like a localised model of global warming. Urban areas are typically warmer than surrounding rural areas, the result of reduced foliage and copious asphalt and buildings that trap heat. Creative ideas for combating the urban heat island are constantly being developed by forward thinking builders and architects. They include rooftop gardens and, increasingly, vertical gardens that hang on the sides of buildings. Gardens use the sun's energy for photosynthesis rather than trapping it as heat and can act as a carbon sink. Also, considerations as simple as a building's colour can have a major effect on localised heat: lighter buildings do not trap heat the way dark buildings do.

The built environment is a huge contributor to global climate change, resource waste, air and water pollution and other environmental ills. It can also be a major part of the solution. The methods for reducing a building's environmental footprint are many and varied. These continue to increase with innovation, technological development and best practices ideas sharing.

Author

Doug Smeath is the Consumer Web Site Marketing Manager at the US Green Building Council, writing and overseeing content for the Green Home Guide and Build Green Schools websites.

Organisation

The US Green Building Council is the US's leading nonprofit organisation composed of corporations, builders, universities, government agencies and other nonprofit organisations working together to promote buildings that are environmentally responsible, profitable and healthy places to live and work. Since its founding in 1993, the Council has grown to more than 12,000 member companies and organisations.

Enquiries

For more information on how to choose green solutions for specific building and development types, visit the USGBC.