The issue about sustainable (green) building is becoming increasingly relevant globally, especially in the real estate sector. A 2013 McGraw-Hill Construction global report found that 51% of architects, engineers, contractors and consultants and building owners‟ surveyed in over 62 countries say it is likely more than 60% of their work will be “green” by 2015 (Initiative for Global Environmental Leadership, 2013).
Urban areas today hold more than half of the human population. They consume three quarters of global energy and responsible for 80% of carbon emission, according to a Schneider Electric white paper, “The Smart City Cornerstone: Urban Efficiency”. The building sector has a major impact on the built and natural environment in that building activities i.e. design, construction and demolition phase directly or indirectly affect environmental performance of the sector. Sustainable buildings are designed to reduce energy, materials, and resources on a life-cycle basis. Leadership in Energy and Environmental Design (LEED) identifies the categories of focus for green buildings to be Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, and Indoor Environmental Quality (Urban Redevelopment Authority, 2012).
The need to design buildings that enhance the environment instead of exploiting it becomes a reality. Driven by the increasing concerns about energy, greenhouse gas emissions and indoor air quality, an explosion in the interest of sustainable building is unmistakable (McGraw Hill Construction, 2008). Sustainable buildings reduce consumption of materials, energy, water, and improve indoor environmental health. The need to reduce the environmental footprint of buildings alongside the economic incentives to build green, presents a substantial opportunity for the real estate and construction sectors.
According to US EPA, OAR, Climate Protection Partnerships Division (2005), Principles of Green Building and Sustainable Site Design include;
- Evaluate site in terms of the location and orientation of buildings and improvements in order to optimize the use of passive solar energy, natural day lighting, and natural breezes and ventilation.
- Help reduce the urban heat island effect by maximizing the use of pervious surfaces, and using light colored roofs, paving, and walkways.
- Provide natural shading of buildings and paved areas with trees and other landscape features.
- Optimize the use of on-site storm water treatment and ground water recharge.
- Use landscape design to preserve and restore the region’s natural habitat and heritage by using indigenous, hardy, drought resistant trees, shrubs, plants and turf.
- Help reduce night-time light pollution by avoiding over-illumination of the site and use low cut-off exterior lighting fixtures which direct light downward, not upward and outward.
- Designing and locating buildings to optimize use of storm water technologies such as bio-retention, rain gardens, open grassy swales underground water storage tanks and pervious bituminous paving.
- Minimize the building’s footprint to absorb and store up to 80% of natural rainfall until it can be absorbed by vegetation or enter the site’s natural sub-surface ground water system.
- Use energy efficient T-8 and T-5 bulbs, high efficiency electronic ballasts, and lighting controls. Incorporate sensors and controls and design circuits so that lighting along 3 perimeter zones and offices can be switched off independently from other interior lights when day lighting is sufficient in perimeter areas.
- Use state-of-the art, high efficiency, heating, ventilation and air conditioning (HVAC) and plumbing equipment, chillers, boilers, and water heaters.
- Optimize the use of natural ventilation and where practical use evaporative cooling, waste heat and/or solar regenerated desiccant dehumidification or absorption cooling.
- Identify ways to reduce the amount of materials used and reduce the amount of waste generated through the implementation of a construction waste reduction plan.
- Identify ways to use high-recycled content materials in the building structure and finishes.
- Use of bio-based materials and finishes such as various types of agri-board (sheathing and or insulation board made from agricultural waste and byproducts, including straw, wheat, barley, soy, sunflower shells, peanut shells, and other materials).
Defining “Green Concept” in Building Design
Earlier research has addressed the incorporation of green building technologies into residential and commercial constructions from multiple points of view. Several authors have examined the financial, social and environmental benefits, in terms of the effects of green design and energy efficiency of “green concept”. Some authors have addressed the cost factors including the decision to adopt energy efficient design as well as the overall cost of building green. Most research has been done by independent institution and organizations specialized in the field of construction and real estate sector.
Many definition of what a green building is or does exist. The ideal “green” project preserves and restores habitat that is vital for sustaining life and becomes a net producer and exporter of resources, materials, energy and water rather than being a net consumer. A green building is one whose construction and lifetime of operation assure the healthiest possible environment while representing the most efficient and least disruptive use of land, water, energy and resources (Governors Green Government Council , 2013). Advances in techniques and materials have made it possible to do what was unthinkable only a few years ago; Design buildings that enhance the environment instead of exploiting it (WaterFurnace International, 2011).An integrated design approach that addresses the potential of the site, water conservation, energy efficiency and renewable energy as well as selection of building materials and indoor environmental quality is used to define a green building.
In 2008, McGraw-Hill Construction (MHC) surveyed firm around the world to gain an insight into global green building trends. The study, “The Global Green building Trends SmartMarket Report, was one of the first ever studies focusing on green building and aiming to discern differences driving the green building marketplace (McGraw-Hill Construction, 2013). Only 17 countries had official or emerging green building councils (GBCs). The World Green Building Council (World GBC) was growing to help the emerging GBC movement the emerging GBCs to share their experiences with other organizations. By 2012, global construction and economic situation was drastically different. After four years of construction activity declines and a global recession, construction activity had shifted to developing countries while developed countries battled with economic challenges. Development of GBCs grew gradually with GBCs in over 90 countries by 2012 including South Africa.
Sustainability is not just about green building design and construction. Cities around the world are in the early stages of mobilizing against the effects of global warming through green infrastructure solutions. Whether a ton of greenhouse gas emission is released in North America, Africa or Asia, its effect on the planet is the same. Reducing those emissions might be achieved a lot more economically with water purification project in Africa than with a roof full of Photovoltaic panels in the United States. That’s the principle behind global carbon markets.
International real estate markets are diverse, embracing green building in different ways and at different levels. According to U.S Government data, building account for 60% of the raw materials used in the United States and 40% of non-industrial solid waste, 65% of electricity consumption, 48% of greenhouse gas emissions and 12% of portable water consumption (Rhall, 2009). California, a state in the U.S was the first to enact a Green Building Code (CalGreen) and is poised to set the standard for greening of residential and commercial structures (Palmese, 2009). The California Public Utilities Commission has set the goal of all new homes meeting net-zero energy standards (producing as much energy as they use) by 2020, with commercial buildings required to meet the same goal by 2030. A study carried out by Kats and his team on 40 California LEED certified buildings showed great gains. There was a reduction in energy consumption, the buildings consumed 28% less than conventional buildings. Water consumption was cut by 50%, of the 21 green buildings studied, 17 reduced construction waste by at least 8% and 8 buildings reduced construction waste by 75%. Operational and maintenance cost were reduced by 5% an average of $3,000/person/year (Urban Catalyst Associates, 2005).
In Vancouver, research indicate that buildings are responsible for a significant proportion of the city’s overall environmental impact contributing to 28% of greenhouse gas emissions, 30% of energy consumption, 12% of portable water consumption and 30-40% of landfill wastes (Vancouver Economic Development Commission, 2009). In 2005 the City of Vancouver passed a mandate that all civic buildings achieve LEED certification. Other policy development which are underway that will emphasize passive design techniques include; green roofs and increasing laneway housing by the year 2030. Vancouver also hosts local green energy expertise e.g. Nexterra which supplied biomass gasification system for Dockside Green, a greenhouse gas neutral residential development located in Victoria, British Columbia (Vancouver Economic Development Commission, 2009).
Green building activity and trends in Africa are slowly gaining recognition. Research shows that Green building is rapidly taking hold in South Africa, with its shares of firms that are dedicated to green building growing at a faster rate than any other part of the world (McGraw-Hill Construction, 2013). This suggests that there is a ripe real estate market in South Africa for green technologies, practices and solutions. In 2012, 31% of construction firms reported their work was green. Overall 16% of South Africa firms report high levels of green in 2012, an eightfold 13 increase in just three years (McGraw-Hill Construction, 2013). South Africa is one of the only countries with a high reported level of green activity in residential marketplace. This indicates that fact that the growth of green building is occurring in tandem with increased urbanization in South Africa.
Green Building Technologies and Fundamentals of Green Buildings
According to the LEED, the five major elements of green building design discussed in this study are: Sustainable Site Design; Water Conservation and Efficiency; Energy Efficiency; Environmental Improvement Quality; and Conservation of Materials and Resources (Rhall, 2009).Blending the right mix of green technologies that cost less with green technologies that cost the same or slightly more, it is possible to have a very green building project that costs the same as a conventional one. The key to a cost effective green building and site design lies within the interrelationships and associated cost and performance trade-offs that exist between different building systems (Governors Green Government Council , 2013).A good example is the interrelationships between the building site, site features, the path of the sun, and the location and orientation of the building and elements such as windows and external shading devices have a significant impact on the quality and effectiveness of natural daylighting. These elements also affect direct solar loads and overall energy performance for the life of the building.
Sustainable Site design
This involves engaging in a design and construction process that minimizes overall site disturbance and which values, preserves and restores or regenerates valuable habitat, green space and associated eco-systems that are vital to sustaining life. The layout and design of a building and site ground has an impact on energy and water consumption. A green planned site will preserve much of the existing natural vegetation, increase energy efficiency and reduce amount of storm water leaving the site (Environmental Science and Policy 763; UWGB, 2004). The amount of excavation required can be reduced, thus reducing construction costs and environmental impacts of the construction process. Key strategies and technologies that can be used include; renovating and re-using existing vacant sites and making efficient use of space in building already in occupational phase. Developers should steer clear of sites e.g. wetlands when new development is unavoidable.
Planners need to evaluate each site in terms of the location and orientation of buildings and improvements in order to optimize the use of passive solar energy, natural daylighting, and natural breezes and ventilation. Reducing the urban heat island effect of the site development footprint by maximizing the use of pervious surfaces, and using light colored roofs, paving, and walkways. Providing natural shading of buildings and paved areas with trees and other landscape features. Optimizing the use of on-site storm water treatment and ground water recharge at site. Minimizing the boundaries of the construction area, avoiding needless compaction of existing topsoil, and provide effective sedimentation and silt control during all phases of site development and construction. Once the construction phase is completed, landscape design should be used to preserve and restore the region’s natural habitat and heritage while emphasizing the use of indigenous, hardy, drought resistant trees, shrubs, plants and turf (Morrish, 2007).
The goal of resource efficiency is to decrease utility bills but the ultimate goal is to save energy (Anderson, 1995). Current technologies and practices offer cost-effective opportunities to reduce energy use by 30-40% in new and existing buildings (Cohen-Rosenthal, 2000).
Residential buildings produce large amounts of carbon dioxide and sulfur dioxide through the direct consumption of electricity and heating fuels. Lighting efficiency can be improved by replacing inefficient incandescent bulbs with new bulb models that have electrostatic ballasts and the use of natural lighting for illumination (daylighting). This can be achieved by using energy efficient T-8 and T-5 bulbs, high efficiency electronic ballasts, and lighting controls.
Incorporating sensors and controls and design circuits so that lighting along perimeter zones or security light of the building can be switched off independently from other interior lights when daylighting is sufficient in perimeter areas (Governors Green Government Council , 2013).
Radiant solar heating is another energy efficient technology within a residential building. In this system dense tiles or concrete are used as flooring or as wall paneling. During the day the floors and walls absorb heat produced by the sun. As the building cools at night, the tiles release the heat energy retained from the day thereby there is no need for air conditioning. In passive lighting a green building would have many large windows that maximize the amount of light admitted into the building. Passive lighting works well with smart lighting; the two systems work together to reduce energy consumption while providing ample light to the occupants of the building. This not only reduces the building’s energy demand by reducing reliance on electricity lighting but also provide better illumination of spaces. However shades should be installed to reduce direct sunlight penetrating the building (Rebecca Brownstone, 2004).
Smart lighting and power saving electronics are a simple way to save energy in a residential building. These devices are designed to shut down when not in use. Smart lights have photo sensors that read how much natural light is in the building and dim electric lights when there is substantial natural light. Smart lights are often equipped with motion sensors so that when there is no one in a room the lights automatically shut off (Rebecca Brownstone, 2004). Use Energy Star certified energy efficient appliances, and home equipment, lighting and HVAC (Heating Ventilation and Air Conditioning) systems. By optimizing the use of natural ventilation and where practical use evaporative cooling, waste heat and/or solar regenerated desiccant dehumidification or absorption cooling energy efficiency can be greatly increased. Home owners should also avoid the use of halogen based refrigeration, cooling and fire suppression systems (Governors Green Government Council , 2013). The benefit to smart lighting and power saving electronics is the reduction in overall energy consumption of the building thus a reduction in energy electricity costs.
The greatest challenge to all energy production is its impact on the environment. Solar power is one of the environmental friendliest ways of producing electricity or heating energy. In grid connected systems, solar power has no effect on the environment, because the system does not include batteries that would need to be replaced (Rebecca Brownstone, 2004). Hot water is the largest component of residential energy cost after heating and cooling (Cassedy, 2000). A well designed water heating system will provide 50-80% of hot water needs depending on the building geographical condition and time of year. Solar water heating system heat water through thermal energy to produce hot water as illustrated in the figure below.
Photovoltaic (solar panels) are green technologies incorporated into residential buildings by using the building‟s individual components i.e. building shell which includes energy efficient windows, lighting, insulation, foundation and the roof. Photovoltaic cells are mounted on the building in grid-connected pattern. The photovoltaic effect is a process in which two dissimilar materials in close contact produce an electrical voltage when struck by light or other radiant energy (Encyclopædia Britannica, 2013). They are noiseless, produces no emissions during operation and vary in size in a totally modular way (Rebecca Brownstone, 2004). This green technology is beneficial in that it reduces energy use by 50% or more, provide thermal insulation on the roofs, protect the roof from Ultra Violet radiation and reduces environmental footprint of the residential building.
The major principle behind water efficiency is preserving the existing natural water cycle and design site and building improvements to emulate the site’s natural “pre-development” hydrological systems. Emphasis should be placed on retention of storm water and on-site infiltration and ground water recharge using methods that closely emulate natural systems. Minimize the unnecessary and inefficient use of potable water on the site while maximizing the recycling and reuse of water, including harvested rainwater, storm water, and gray water (Governors Green Government Council , 2013).
During site assessment effort should be made to preserve areas of the site that serve as natural storm water retention and ground water infiltration and recharge systems. Preserve existing forest and mature vegetation that play a vital role in the natural water cycle by absorbing and disbursing up to 30% of a site’s rainwater through evapo-transpiration. Optimizing the use of low-impact storm water technologies such as bio-retention, rain gardens, open grassy swales, pervious bituminous paving, pervious concrete paving and walkways, constructed wetlands, living/vegetated roofs, and other technologies that support on-site retention and ground water recharge or evapo-transpiration (Governors Green Government Council , 2013).
Water is often consumed with little or no consideration of the viability of water resources. As a result most areas face shortages in portable water supply. Increasing water efficiency can reduce water-supply and wastewater-treatment needs and their related costs (Houle Insulation Inc, 2013). The most basic start to water conservation is stopping leaks which account to up to 10% of the water wasted in residential homes. Installing water efficient toilets will result in significant water efficiency. Toilets represent a residential home largest water consuming device. Using energy star certified washers with a water factor below 9.5 will use as little as half the amount of energy and water of a non-star washing appliance (California Urban Water Conservation Council, 2013). Dual-flush toilets should have two buttons that release different amounts of water for either liquid or solid waste should replace older models of toilets. These toilets use 6 liters for solid waste and 3 liters for liquid. The average flush volume is approximately 3.8 liters/flush compared to older models that use up to 13 liters/flush resulting in 67% savings in water.
A rainwater collection system is a simple green technology for the operation of a residential building to conserve water use. The rainwater is collected as it runs off the building and would be stored in cisterns until it is needed. The water can be used to water the rooftop garden, or treated for potable uses within the building (RainwaterHarvesting.Org, 2013). There environmental benefit of this technology is the reduction on load on municipal storm sewers and less demand on freshwater resources. Other green technologies used to conserve water and preserve ground water quality is by using only indigenous, drought resistant and hardy trees, shrubs, plants and turf that require no irrigation, installing waterless urinals and aerated faucets.
Green roofs are light weight, engineered roofing systems with low maintenance plants accessible as a rooftop garden that protect the integrity of the roof while at the same time providing many benefits such as storm water management and energy efficiency. Energy efficiency is ensured by the reduction in heating due to fewer fluctuations in roof temperature and insulating properties of vegetation. Green roofs also ensure extension of roof life through protection of the roof membrane from ultra violet radiation and the continued expansion and contraction due to fluctuating temperatures (Eisenman, 2004). Other benefits of green roofs are noise reduction, storm water retention taking load off municipal storm sewers during rainy season, improved air quality in the residential building and providing habitat for other organism e.g. birds, butterflies. Residential buildings with green roofs also have increased property values (Rhall, 2009).
Environmental quality, materials and resources
Providing a healthy, comfortable and productive indoor environment for building occupants and visitors through a residential building design, which affords the best possible conditions in terms of indoor air quality, ventilation, and thermal comfort, access to natural ventilation and daylighting, and effective control of the acoustical environment is the major principle behind this green initiative (Governors Green Government Council , 2013). This green initiative can be achieved by use of building materials, adhesives, sealants, finishes and furnishings which do not contain, harbor, generate or release any particulate or gaseous contaminants including volatile organic compounds harmful to human health and wellbeing. Energy certified ventilation systems capable of effectively removing or treating indoor contaminants while providing adequate amounts of fresh clean make-up air to all occupants and all regions of the residential building. This appliances monitor indoor air conditions including temperature, humidity and carbon dioxide levels, so that building ventilation systems can respond when space conditions fall outside the optimum range.
Designing building envelope and environmental systems that not only treat air temperature and provide adequate ventilation, but which respect all of the environmental conditions which affect human thermal comfort and health, including the mean radiant temperature of interior surfaces, indoor air humidity, indoor air velocity, and indoor air temperature (Cohen-Rosenthal, 2000).
Preventing contamination of the building during construction involves taking steps to minimize the creation and spreading of construction dust and dirt. Prevent contamination of the building and the buildings heating, cooling and ventilation systems during the construction process. Protect construction materials from the elements so that they do not become damp, moldy or mildewed. The main essence of this initiative is to provide a clean and healthy building. Residents should use biodegradable and environmentally friendly cleaning agents that do not release harmful agents and residue. Prior to occupancy install new air filters in the HVACs and clean any contaminated ductwork and ventilation equipment. Use fresh outdoor air to naturally or mechanically purge the building of any remaining airborne gaseous or particulate contaminants (Governors Green Government Council , 2013).
Green buildings normally minimize the use of non-renewable construction materials and other resources through efficient engineering, design, planning and construction and effective recycling of construction debris. It also maximizes the use of recycled content materials, modern resource efficient engineered materials, and resource efficient composite type structural systems wherever possible. Maximize the use of re-usable, renewable, sustainably managed, bio-based materials. Key strategy and technology behind green material and resources is to identify ways to reduce the amount of materials used and reduce the amount of waste generated through the implementation of a construction waste reduction plan. Adopt a policy of “waste equals food” whereby 75% or more of all construction waste is separated for recycling and used as feedstock for some future product rather than being land filled. Implementing an aggressive construction waste recycling program and providing separate, clearly labeled dumpsters for each recycled material will ensure maximum resource efficiency (McGraw-Hill Construction, 2013).
Contractors should thereby identify ways to use high-recycled content materials in the building structure and finishes such as blended concrete using fly ash, slag, recycled concrete aggregate, or other admixtures to recycled content materials such as structural steel, ceiling and floor tiles, carpeting, carpet padding, sheathing, and gypsum wallboard. Green contractors go a step further and explore the use of bio-based materials and finishes such as various types of agri-board (sheathing and or insulation board made from agricultural waste and byproducts, including straw, wheat, barley, soy, sunflower shells, peanut shells, and other materials) (Governors Green Government Council , 2013). Some structural insulated panels are now made from bio-based materials. Use lumber and wood products from certified forests where the forest is managed and lumber is harvested using sustainable practices thus ensuring sustainable forest management practices.
Leadership in Energy and Environmental Design (LEED) is an internationally recognized green building certification system providing third party verification that a building or community was designed and built using strategies aimed at improving performance across all the metrics that matter most: energy savings, water efficiency, CO2 emissions reduction, improved indoor environmental quality, and stewardship of resources and sensitivity to their impacts.
Environmental and social benefits of residential green buildings
Green buildings provide a healthy, comfortable and productive indoor environment for building occupants and visitors and the best possible conditions in terms of indoor air quality, ventilation, thermal comfort, access to natural ventilation and daylighting, and effective control of the acoustical environment as discussed in this study. A recent Lawrence Berkley National Laboratory Study reported that commonly recommended improvements to indoor environments could reduce health care costs and work losses from communicable respiratory diseases by 9-20 percent, among other benefits. By promoting the need and use of recycling construction material a lot of stress is alleviated from extraction and utilization of environmental resources thus conservation and reuse of materials and resources. As domestic fossil fuel supplies are depleted and energy resources getting expensive as each day passes, our nation becomes more dependent on sources from foreign countries. Energy-efficiency and renewable energy sources I green buildings can lessen this dependence and help improve national resource security (WaterFurnace International, 2011).
Financial Benefits of Green Buildings
Higher selling potential in the real estate sector due to health effects on inhabitants, durability and ease of maintenance, environmental friendliness, and energy efficiency associated with green buildings (Jeff Martin, 2007). Savings in energy of 20-50 percent are common through energy-saving technologies, integrated sustainable green initiatives. Increased value for developers and owners due to a growing confidence in the industry that a high-performance green building can either capture lease premiums or present a more competitive property in an otherwise tough market. Green buildings reduce the stretch on local infrastructure capacity. Decreased energy and material requirements coupled with appropriate siting help stretch the capacity of overburdened public systems for grid supplied power, water, wastewater/storm water management (WaterFurnace International, 2011). Opportunities for investments from public equity markets should surge as greener building product comes to market for purchase and green product definitions become more standardized. The growing market acceptance of LEED as industry standards in more countries should help in this regard. Low utility bills due to energy and water efficiency brought about by incorporating green building technology and strategies.
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