Green buildings, also known as sustainable building or green construction, is the practice of building structures that are environmentally responsible and resource efficient throughout buildingâ€™s life cycle, from sitting to design, construction, operation and maintenance. Considering how green structures impact the environment is through studying variety of aspects, sources and materials being consumed and finally the effects on the environment. We will firstly discuss the aspects contributing in green structures, life-cycle of structures go over the stages of sitting, design, construction, operation, maintenance, renovation, and finally to the end of lifespan of the project (deconstruction). The sources that are being utilized are materials, water, energy and natural resources. We concentrate our focus on the environmental effects such as wastes, water pollution, air pollution and storm water runoff, leading to the ultimate effects of degradation and harm to the human being health and environment, in addition to the loss of utilized recourses. The purpose of building such structures is to minimize the harm that regular buildings have on the environment and to be conservative using resources and energy throughout strategies: such as using passive solar energy, water recycling, natural and local construction materials and renewable energy. In other words, green structures could help in:
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Minimizing the amount of air and water pollution, wastes and degradation of the environment. I.e. recycling wastes.
Protecting tenants and even workers. E.g. reducing emissions which results in improving workers productivity, and yet, the quality of work done by them.
Indoor environmental quality enhancement
The Indoor Environmental Quality (IEQ) category in LEED standards, one of the five environmental categories, was created to provide comfort, well-being, and productivity of occupants. The LEED IEQ category addresses design and construction guidelines especially: indoor air quality (IAQ). (www.wikipedia.org)
Indoor Air Quality seeks to reduce volatile organic compounds, or VOC's, and other air impurities such as microbial contaminants. Buildings rely on a properly designed HVAC system to provide adequate ventilation and air filtration as well as isolate operations (kitchens, dry cleaners, etc.) from other occupancies. During the design and construction process choosing construction materials and interior finish products with zero or low emissions will improve IAQ. Many building materials and cleaning/maintenance products emit toxic gases, such as VOC's and formaldehyde. These gases can have a detrimental impact on occupants' health and productivity as well. Avoiding these products will increase a building's IEQ. (www.wikipedia.org)
One of the major aspects in providing an optimum indoor climate in buildings is Ventilation. Indoor Air Quality is determined by the performance of the ventilation system. Air movement inside the building has a significant importance for thermal comfort, especially in summer conditions. Therefore, ventilation may strongly have an effect on the energy efficiency of green buildings.
Indoor Air Quality
Sick building syndrome and building related illness:
Sick Building Syndrome refers to the situation in which building occupants experience some health problems linked to time spent in a building. These complaints may be in a particular room, zone or throughout the building area. The symptoms experienced by occupants may be:
Headaches, lethargy, lack of concentration, runny nose, dry throat, eye and skin irritation.
Causes of these symptoms remain unknown.
Symptoms disappear soon after leaving the building.
Building Related Illness refers to the diagnosable illness and the causes of these symptoms can be attributed directly to building contaminants.
Many parameters have been investigated in order to understand the causes of sick buildings, focused in four major areas:
Ventilation systems: Air distribution, ventilation rates, filtration, maintenance of the duct system.
Building contaminants: smoke, humidity, dust, carbon dioxide, asbestos.
Occupants: age, gender, state of health, occupation.
Miscellaneous: lighting, noise, stress, electromagnetic radiation, psychological factors.
Researchers have shown that ventilation has the most significant role in these problems since ventilation rates are very low.
Indoor pollutants result from both indoor and outdoor sources. Indoor pollutant sources are either natural or result from human activities. However, air pollutants may differ from one building to another according to the design and purpose of the structure.
Outdoor sources are known to be:
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Industrial emissions: oxides of nitrogen and sulphur, ozone, lead, Volatile Organic Compounds (VOCs), smoke, particles and fibres.
Traffic pollution: carbon monoxide, carbon dioxide.. etc
Nearby pollutants such as emissions of cooling towers when located close to air sources
Soil borne pollutants.
The major indoor pollutants arise from three main sources:
Human and animal metabolism.(responsible for the omission of carbon monoxide and dioxide)
Occupant activities such as smoking tobacco which is a complex mixture of several thousands of compounds, more than 40 of which are known to cause cancer and many of which are strong irritants.
Building materials and equipment, which are responsible for the Omission of formaldehyde.
Green buildings aim to reduce the air pollution concentration within a building by a variety of different approaches, starting with controlling outdoor air pollutants, then indoor air pollutants. It is done using ventilation systems since it is the optimum solution to purify the air from impurities and toxic gasses.
Outdoor pollutants can be controlled by:
Filtration: ventilation systems can incorporate filters preventing impurities from outside entering the ventilation system.
Fresh air dampers controlled by air quality: closing fresh air dampers temporarily during traffic pollution peaks.
Indoor pollutants can be controlled by:
Source control: aims to eliminate avoidable pollutants by restricting toxic emissions.
Ventilation is the process of recycling the air within the structure, as it helps improve indoor air quality. It prevents the accumulation of toxic gasses in the building envelope and building equipment. It also ensures good indoor conditions for the health and comfort of occupants. There are two types of ventilation:
Natural ventilation which includes the movement of air from the outdoor through doors or windows, exiting through unintentional openings on the opposite side.(Fig.1)
Mechanical ventilation which is supplied by electric fans, usually included in a building HVAC system.(Fig.2)
(Figure.1) Natural Ventilation
(Figure.2) Mechanical Ventilation