Whenever I mention the word ‘green building’ to many people who are outside the professional realm of green building and sustainable construction, the reaction and responses I receive for what they understand is a green building are often divergent. The two most conceived meanings of a green building are either a greenhouse (for farming) or a house powered by renewable energy, which is not a very wrong answer but it is not entirely correct as it leaves other major aspects of a building uncared for, environmentally speaking. There is a third simple response though, a normal house painted in green colour.
A green building encompasses much more than these responses. In the widest of definitions, it is any building built with numerous eco-friendly strategies. It is one that is resource efficient, does less harm to the environment and consumes less energy (energy-efficient). Simply powering your home with solar panels in the strictest of definition does not qualify a building to be a green building. Although it has satisfied a major aspect of what makes many buildings unfriendly to the environment and climate, other aspects such as the site it was built, how water is used in the building, materials used in the construction and a host of other things also need to be environmentally assessed.
A green building is one that employs environment friendly strategies from the planning, design, construction, usage, renovation and deconstruction.
A number of countries like the US, UK, South Africa, Japan, Australia etc. have developed green building rating systems to certify whether a building is green or not, based on achieving a number of points that accrue based on how eco-friendly it is. For the most part what is assessed in every building to say whether it is green or not, the following are normally checked.
Site Selection and Analysis
The choice where to put up your house, prevailing climatic and micro-climatic conditions, site topography and presence of vegetation helps to guide builders in achieving the status of the green. In Abuja, the city I live, years back, developers where converting green areas (sites planned to be used as green parks) to residential and commercial purposes. Some others convert arable and Greenfield sites. These choices are detested when aiming to design green. The urban ecology should not be harmed or disturbed to that extent.
The direction of the sun should be taken in to consideration. Understanding where the sun passes throughout the year will reveal valuable information of solar heat gain into the house, use of daylighting and shading of buildings (including neighbouring buildings). Many of these are better understood by architects and engineers. But the major take away from this is, for buildings in temperate regions like Nigeria, we do not want heat into the buildings, so designers must at all cost orient the building to keep the sun out, while maximizing its rays for daylight.
Wind conditions, speed and direction, must be known in order to design for optimum natural ventilation. In essence, wind conditions and sun path are used in order to maximize the merits of the existing micro-climate.
This is different from what the site analysis does, but it incorporates the results of the analysis in choosing a proper building orientation, building position, building carbon footprint and drainage.
Buildings in temperate regions should be oriented in the east-west axis. Where the building has major facades should not be directly receiving the sunlight, but the wind.
When site conditions are fully understood, the design of the building should reflect the results. Use of natural ventilation and natural lighting should be maximized. Size of facades should be made big in case of temperate places like Nigeria, to allow for more of this natural ventilation and let in more sunlight.
Material selection has huge implications on how green a building is. A green building will consider a life cycle assessment of materials used. From extraction, production to transportation. Using locally available building materials is highly desirable in order to reduce transportation cost and pollution and also supporting local economy. Material composition will also affect energy consumption of the building. Some materials like stones and concrete store a lot of heat and thus heat the building in the night. Wood on the other-hand does not. The choice of the materials will depend on the existing microclimate.
Resource Use; Energy, water, waste
A green building may be defined as a resource efficient building. How it uses water, energy, generate and dispose waste says a lot about how green a building is. For energy, use of renewable sources for power supply is important. Electrical appliances that consume less energy like LED bulbs are more desirable. LEED, which is a green building rating systems, assigns the most points for the energy consumption of buildings.
Water is another vital resource that needs careful management to show that a building is environment friendly. Water efficient buildings have low usage of water, recycles waste water and even collect rainwater from their roof.
The last major resource to consider in managing is waste that is going to be generated. Waste water treating and recycling as discussed in water efficiency above is a major part of it. Solid waste is a major thing to consider. For most green buildings, sorting of wastes and composting are the major solutions. Waste is sorted into perishables (food), paper, plastic (PET), glass and metal etc. mostly sorting is based on the waste management of the city. For some cities not practicing this, a good way a green building can take care of its solid waste is to compost it.
These enumerations and major features form a big chunk of designing a green building. Any green building should address these highlighted issues, although a number of other features exist that need to be addressed by the green building designers.
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