Environmental Impact Research Misr International University Presented to: Dr. Ola el Baki
Presented by: Karim Fahmy 12/4647 Toka Ashraf 12/3223 El Hussein 12/5766 Walid 12/5934 Serag 12/0819 Ziad Labib 12/1638 1
Chapter 1 Sustainability and Green Building Design 1.1 sustainability……………………………………………………… Pg.3 1.2 green building design…………………………………………….. Pg.4
Chapter 2 sustainable site landscaping 2.1 sustainable site …………………………………………………… Pg. 9 2.2 Sustainable Landscaping………………………………………….
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Chapter 3 passive energy design 3.1 grouping of building……………………………………………… 3.2 orientation of building……………………………………………
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3.3 building form…………………………………………………… 3.4 building envelop…………………………………………………
Pg. 21
3.5 passive cooling…………………………………………………
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3.6 natural ventilation paths……………………………………….
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3.7 daylighting………………………………………………………
Pg 34
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Chapter 1 – Sustainability & Green Building Design 1.1
Sustainability
1.1.1 Introduction â–Ş
Sustainability is a method of harvesting or using a resource so that the resource is not depleted or permanently damaged. It is also involving methods that do not completely use up or destroy natural resources.
1.1.2 Importance of sustainability Sustainability is important because all the choices we pursue and all the actions that we make today will affect everything in the future. We need to make sound decisions at present in order to avoid limiting the choices of generations to come.
For example, if you continue wasting water and polluting the dwindling supply of freshwater that we have today, we leave future generations with no other choice than to desalinate saltwater or treat contaminated water for their consumption and daily use. We can also be assured that, if that happens, all life that depends on clean freshwater will become extinct. The same goes with the supply of soil that we currently have. Without proper care, our soils can easily lose quality enough that they will no longer be able to encourage growth and sustain life. If that happens, future civilizations will be void of crop and other natural sources of food. They will then have no other choice but to create man-made sources for nourishment and sustenance.
Sustainability is important when it comes to the reduction of power consumption as power is manufactured using oil and other non3
renewable sources then these sources will soon be depleted. The next image shows the power consumption from different sources through the past years, informing us of the majority of depletion mostly in sources that are non-renewable.
1.2
Green Building Design
1.2.1 Definition and importance of green building Green building is the practice of creating structures and using processes that are environmentally responsible and resource-efficient throughout a building's life-cycle from siting to design, construction, operation, maintenance, renovation and deconstruction. This practice expands and complements the classical building design concerns of economy, utility, durability, and comfort. Green building is also known as a sustainable or high performance building.
1.2.2 Environmental Benefits •
Enhance and protect biodiversity and ecosystems
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Improve air and water quality
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Reduce waste streams
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Conserve and restore natural resources
1.2.3 Economic Benefits •
Reduce operating costs
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Improve occupant productivity
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Enhance asset value and profits
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Optimize life-cycle economic performance
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1.2.4 Social Benefits •
Enhance occupant health and comfort
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Improve indoor air quality
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Minimize strain on local utility infrastructure
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Improve overall quality of life
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Green Building Programs
LEED, Leadership in Energy & Environmental Design, is the nationally accepted rating system for commercial and institutional green buildings. The program helps establish a standard measurement for green building. Contact the US Green Building Council for more information www.usgbc.org/leed/http://www.usgbc.org/leed/ Green Built NC Homes Certification Program is a state-wide residential green building rating program administered by the WNCGBC. Homes receive a rating and certificate based on third party inspections.
1.2.5 Green building methods
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This building shows the methods of green buildings. Using as much renewable energy and natural resources to provide for the building’s needs. For the energy consumption the building uses solar panels to convert sun light into energy and electricity. To recycle and use less water consumption the roof gathers the rain water and stores it’s for internal use inside the building and plant watering. To further reduce power consumption more efficient products are used inside the building like efficient dish washers and efficient light fixtures. To reduce need for building cooling, the roof is fitted with high quality insulation.
1.2.6 Green building example Example 1 Location: Australia, Melbourne Area: 130,000 sqm Architects: Hassell Project year: 2010
Method 1 1000 m2 of solar cells on the building’s roof supply renewable energy
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Method 2 Roof mounted wind turbines supplement electricity generated on-site
Method 3 Tri generation: The building will produce 70 per cent less greenhouse emissions than other commercial buildings. It will tap gas-fired energy Electricity will be generated on-site using natural gas. Heat from the process feeds air conditioning absorption chillers in the summer, and the boilers for heating in winter
Method 4 Energy efficient air conditioning system maximizes the use of fresh air providing healthy working environment
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Method 5 Exterior sun shading maximizes daylight while reducing heat gain and loss
Method 6 Air conditioning systems use cool water from the river, reducing demands on cooling towers
Method 7 Rainwater harvested from building’s roof area is used to irrigate surrounding gardens
Method 8 Wastewater is recycled for use in building infrastructure, such as toilet flushing
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Chapter 2 sustainable site & landscaping 2.1 Sustainable Site: A sustainable site plan takes the impact of the building on the surrounding environment and its intended occupants. Site selection and design play important roles in both reducing greenhouse gas emissions and helping projects adapt to the effects of climate change. Sustainable design projects will start in one of two ways first one: the team starts with a site and considers the best functions and uses for that particular location. Second one the team starts with a function and determines the best location for that land use. The last method is better because as the design team choose the best matching land for the nature of the project, not losing any of the land features. A functional and attractive design will be unique to a specific site and should be based on a careful review process.
2.1.1 Site choosing: There is many attribute was put in order to select a better and more sustainable site for a new project take in consideration. First of all the local climate of the project. In addition it is more preferable to choose a site that was that was previously developed. If the site is in use for the first time then the construction team has to study the different species using it as habitat or a place to get food from. If it was found so, it is a must to make an alternative for their needs or choose another site. In order to remain the economical sustainability the building should be connected to local infrastructure and public transportation. Also, to study the nature of the street life in the area, where people live and work and how can the project contribute to the community. If people can use public transportation, ride bicycles, or walk to the building, the project helps reduce the carbon emissions associated with commuting. A project that is connected to the community by pedestrian paths and bicycle lanes encourages people to walk or bike instead of drive, not only helping to reduce air pollution, but also promoting physical activity. All that would tell how much is the quality of this site from the sustainability point of view.
2.1.2 Site choosing importance: The location and site of a building are as important as how the building process has been done. How the building is connected to local natural environment, watershed, and community will help 9
determine how a project can contribute to a sustainable environment that do not harm the ecological system. A sustainable project serves more than the immediate function of the building. It may extend to include the local community needs, supporting a more active street life, promoting healthy lifestyles. Also, to provide ecosystem services making ecological benefits from the building, not only make it as it is and ignore the style or the place which is built in.
2.1.3 Green Paving system Case study of landscape area that use the solar energy as natural way for getting energy Parking Lot in America In America there was a vision of replacing the asphalt of American roadways and parking lots with energy producing solar panels. "Solar Roadways" is the American company that has just unveiled their first parking lot made of hexagonal solar panels. These panels are made of 69% of solar panels under each piece of glass. Those panels are very strong to carry on the weight of passing vehicles. Cycle lane in Netherlands In Netherlands sola Road Company was trying the first cycle lane made up of solar panels. It is a 70 meters long cycle path that generates solar power from rugged, textured glass-covered photovoltaic cells.
2.1.4 Minimizing building footprint A smaller footprint means less impact on the site. A sprawling one-story house takes up more of the lot than a two-story house of the same square footage. That leaves more room for plants and 10
wildlife, and better absorption of rain and snow runoff. In addition, smaller houses use fewer materials and cost less to operate. Code and zoning restrictions, including solar access regulations, may limit building height
2.1.5 Erosion control
Allowing for heavy equivalent axle loads without fear of lateral movement of the fill material. Compact sections of sand soil filling can thus replace truckloads of crushed stone or other granular fill or even asphalt or concrete. Then minimize its bad effect on the environment.
2.1.6 Design strategy Passive design is the design of the building’s heating, cooling, lighting, and ventilation systems, relying on sunlight, wind, vegetation, and other naturally occurring resources on the construction site
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2.1.7 Day lighting Architects responded by a whole topology of window and roof light designs, readily accepting the need for shallow plans, light wells and courtyards. This constraint was also reinforced by the same need for shallow plan to achieve good natural ventilation. The effective use of louvers, low-emissivity glasses, and slanted ceilings will help in creating a stimulating environment which increases productivity. The basic target of any design should be increase the dependence on natural day lighting and minimizing the use of artificial lighting
2.1.8 Passive ventilation Natural ventilation is gaining prominence of late to mechanical ventilation or full-air conditioning. Wind generates pressure differences across the constructed environment through openings in the building envelope. Furthermore the temperature differences between the interior and the exterior of the building causes a vertical pressure gradient which causes air to flow vertically – if the wind inside is warmer than that of the outside then natural ventilation occurs
2.2 Sustainable Landscaping In order to produce a long lasting sustainability system, ecological system has to be merged with design elements like landscape design.
2.2.1 Sustainable landscaping meaning and concept A sustainable design should provide balance between the local climate and the attractive environment the user want all that with minimal quantity of expandable resources like time. Gasoline, clean water or fertilizer. Sustainable landscaping requires suitable design .with the three aspects of sustainability that includes functional, cost efficient. Visually pleasing. Environmentally friendly and maintainable areas. 12
For sustainable landscaping there are short-term goals as well as long-term goals. For instance, a short-term goal may include saving water or installing and using a compost bin. Composting locally grown crops and kitchen waste and returning it back to the garden increasing soil organic matter and helps plant growth. A long-term goal may be to create a more self-sustaining garden. This includes all aspects of total plant health care with a proper plant selection, reducing the garden inputs. In order to accomplish the long term success. A set of short- term goals should be put. By achieving these goals the long term goal will be achieved too.
2.2.2 Advantage of sustainable landscape: In addition of the attractive look the sustainable landscaping give, it conserve natural resources that may be wasted. Also maximizing ecological function and Reduce pollution
2.2.3 Green Roofs A green roof system is an extension of the existing roof which involves a high quality water proofing and root repellant system, a drainage system, filter cloth, a lightweight growing medium and plants. Green roof systems may be modular, with drainage layers, filter cloth, growing media and plants already prepared in movable, often interlocking grids, or loose laid/ built-up where each component of the system may be installed separately. Green roof development involves the creation of "contained" green space on top 13
of a human-made structure. This green space could be below, at or above grade, but in all cases the plants are not planted in the "ground'. Green roofs can provide a wide range of public and private benefits.
2.2.4 Public Benefits Urban greening has long been promoted as an easy and effective strategy for beautifying and get that attractive looking of the built environment and increasing investment opportunity achieving economical sustainability. Green roofs can contribute to landfill diversion by: Prolonging the life of waterproofing membranes, reducing associated waste The use of recycled materials in the growing medium Prolonging the service life of heating and ventilation.
2.2.5 The green walls The term "green walls" comprises of all forms of vegetated wall surfaces. It is a living garden growing, decorating, on a wall. Vertical Landscapes can be made to fit any wall, apart from of its shape or size. Some of vertical Landscapes are designed to be modular, allowing quick and easy installation and removal. Vertical Landscapes are installed as fully planted gardens, with everything required to keep the wall always green and covered with plants. There are three major system categories that fall under this term's rubric: green faรงades, living walls, and retaining living walls.
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2.2.6 Green Façades Green façades are systems in which plants are growing on the wall climbing the supporting structures that are purposely designed for their location. Plants growing on green façades are generally rooted in soil beds at the base of the supporting structure, in elevated planters at intermediate levels, or on rooftops. Depending on climate, choice of species, depth of soil bed, orientation, nutrition and irrigation regime, green façades may take several seasons before achieving maturity. Green façades can be attached to existing walls or built as freestanding structures. They are used to shade glazed façades. Also, to provide kind of privacy and security. Could be added to screens or decorating parking structures, patios and walkways, and are built as arbors, trellis structures, baffles, or fences.
2.2.7 Living Walls Living wall systems are composed of pre-vegetated panels, modules, planted blankets or bags that are affixed to a structural wall or free-standing frame. These modules can be made of plastic, synthetic fabric, clay, or concrete and support a greater diversity and density of plant species than green façades. To date many living wall installations can be found in both tropical and temperate locations. Living walls can perform well in full sun, shade and interior applications.
2.2.8 Retaining living walls Retaining living walls are engineered living structures that are designed to stabilize a slope, while supporting vegetation contained in their structure. They provide the structural strength to resist the lateral forces exerted by angles greater than the natural angle of repose of soil and protects slopes against erosion. Some systems can perform on slopes up to 88 degrees and many have capacity for variable slope angles as flat as 45 degrees. The growing plants must be sheltered from erosion, be accessible to the introduction of plant material either from plugs or seed and provide for long term plant growth. The mature living retaining wall is intended to be fully covered by its internally supported vegetation such 15
that the underlying structural elements are no longer visible as the wall becomes additional green space and habitat for the project.
2.2.9 Benefits of vertical landscape: 1. Save Space Vertical Landscapes allow the planting of gardens in apartments, foyers, terraces and other places where floor space is limited.
2. Air Quality Improvement Vertical Landscapes absorb gaseous pollutants and breathe in carbon-dioxide through photosynthesis, while trapping airborne particulate matter. The plants breathe oxygen into the air leading to reduced air-conditioning requirements and reduced greenhouse gases, thereby lowering your carbon footprint.
3. Building Protection and Insulation Vertical Landscapes insulate buildings against noise and outside temperature changes, leading to significant air-conditioning savings, then reduce energy costs, and extension of the building envelope life. Vertical Landscapes shield buildings from ultra-violet rays and acidic rain. Reduce energy costs with natural insulation and absorb storm water
4. Ecological benefits Vertical Landscapes provide protected spaces for birds, bees and butterflies, creating peaceful retreats for people and animals, contributing to biological diversity
5. Reduction of Heat Island Effect Heat Islands are a phenomenon caused by the centralized heat produced by our cities through vehicle exhaust, air conditioners, and massive quantities of heat-absorbing asphalt and concrete. Vertical Landscapes directly reduce this effect. When moisture evaporates from plants, heat is consumed. In addition Green roofs last longer than conventional roofs
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2.3 California Academy of Sciences
The Academy make new building that would reinforce its mission to “explore, explain, and protect the natural world”
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the museum opened its remarkable new facility on the site of the old complex., the new building sets a model for how to integrate sustainable technologies and natural systems through innovative design while at the same time educating the public about green buildings
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The living roof’s 3,500 square-foot observation deck is one of the museum’s most popular exhibits. Here, patrons learn how the green roof reduces storm water runoff by more than 90 percent, lowers energy needs for air conditioning, and doubles the life of the roof membrane.
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The living roof was planted with 1.7 million native California plants. By incorporating plants that are well-adapted to the local ecosystem, this landscape requires little irrigation and attracts numerous species of birds, butterflies, and insects. Dozens of round skylights dot the roof of the rain forest dome and allow natural light to filter through to the exhibits below.
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• In summer, the roof opens to allow cool night air to flow into the building below. By using natural ventilation instead of air conditioning to regulate interior temperature, the building becomes more energy efficient. • While less recognized, the museum’s entrance plaza and landscape form a second green roof on top of two levels of underground parking. With soil depths between 2 and 4 feet, this “intensive” green roof is deep enough to plant trees. By taking on the form and function of a public park, this green roof is more usable and pedestrian-friendly than a traditional parking lot roof deck.
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Chapter 3 Passive Energy Design 3.2 Building orientation 3.2.1 Importance of building orientation Design for orientation is a fundamental step to ensure that buildings work with the passage of the sun across the sky. Knowledge of sun paths for any site is fundamental in design building facades to let in light and passive solar gain, as well as reducing glare and overheating to the building interior. It is important to remember that the position of the sun in the sky is dynamic, changing according to time of the day, time of year and the site's latitude. Building orientation is the practice of facing a building to maximize certain aspects of its surroundings, such as street appeal, to capture a scenic view, for drainage considerations. For developers and builders, orienting a new home to take advantage of the warmth of the sun will increase the home's appeal and marketability. Well-orientated buildings maximize day lighting through building facades reducing the need for artificial lighting. Some typologies especially housing can be zoned to ensure different functional uses receive sunlight at different times of the day. Buildings that maximize sunlight are ideal for the incorporation of passive solar collection techniques that can reduce carbon use and enhance user comfort. A careful strategy can also mitigate overheating and glare when sunlight is excessive. You should know how the sun interacts with your building in high summer and the depths of winter.
3.2.2 Sun’s Variations in Position Can Affect Building Design The relative position of the Sun is a major factor in heat gain in buildings, which makes accurate orientation of the building a fundamental consideration in passive solar construction.
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Most importantly, a rectangular house’s ridgeline should run east-west to maximize the length of the southern side, which should also incorporate several windows in its design. For this reason, fewer windows should be located on the northern side of the house, where the summer sun can be intense. A deep roof overhang can shade the few windows in this area, as can different types of shade trees and bushes. Research supports an east-west ridgeline. Homes re-oriented toward the Sun without any additional solar features save between 10% and 20% and some can save up to 40% on home heating, according to the Bonneville Power Administration and the City of San Jose, California. Builders should note that these directions are given in reference to the Sun and not magnetic north, which can vary significantly from the Sun’s actual position. Magnetic north, as read from a compass, can still be used as a reference if the builder adjusts the figure based on the locationspecific magnetic variation, which can be found in publicly available maps Office buildings typically are about the reduction of excessive solar gain and glare. This is because of a greater preponderance of glazed facades and also higher internal gains from people, computers etc. Use glazing due south sparingly and incorporate shading devices.
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3.4 Building envelope 3.4.1 about the building envelope concept Humans first created shelters to provide thermal comfort and protection from natural elements, and this still remains a primary objective of buildings. The building envelope is the physical separator between the interior and exterior of a building.
Components of the envelope are typically: walls, floors, roofs, fenestrations and doors. Fenestrations are any opening in the structure: windows, skylights, clerestories, etc. When designing the building envelope, knowing some fundamentals of building materials and heat transfer will help you make the right trade-off decisions. Climatic changes affects the building envelope creating a different type of materials used to protect against different elements such as dry-hot, cold, mild, cold .. Weather.
3.4.2 Arid Climate Envelope Arid climates are very dry, and usually hot, but they often have large swings of temperature from day to night (tends to get colder). Thus thermal mass on the outside of the building is the most crucial design strategy to even out such temperature swings. For consistently hot locations, it also helps to have high ceilings, shaded breezeways, light colors, and daylighting by using reflected light (not direct sun), such as the famous Egyptian architect Hassan Fathy’s buildings as shown. Courtyards with natural ventilation and pools or fountains can provide evaporative cooling as well, which 21
also tends to have much thicker walls reaching 88cm thick walls, this helps stopping the heat from transferring inside the space fast at day but then when it comes to night the heat finally gets to penetrate the thick walls warming up the rooms because the climate tends to get colder at night. Another element used in this climatic condition are the domes and vaults, which increases the mass of the building also creates many shaded areas on the roof which is exposed to the direct sunlight. Also as a part of this climate building envelope are the atriums and courts which sometimes are exposed directly to the sky or closed with a clerestory with opened ventilations to create a natural crossventilation system in the building creating a more satisfactory environment to live in, it was also used in the old days to create a natural refrigerator-like system to cool the drinkable water which is placed near the ventilation system, and some other methods to create a more humid atmosphere is to introduce a water element inside the building.
3.4.3 Tropical Climate Envelope Tropical climates are hot and humid. Therefore, keeping the heat of the sun off is the top priority, as well as maximizing ventilation— essentially a reflective insulated roof with walls that pass breeze but not rain is ideal. This traditional Papua New Guinean home’s thick light-colored thatch roof keeps out the sun’s heat, while open eaves and porous bamboo slats for walls and floor maximize natural
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ventilation. The materials are all low-mass to avoid condensation and mold growth, which can happen with high-mass materials in humid climates.
3.4.4 Cold Climate Envelope Cold climates have many more heating degree days than cooling degree days. Thus maximizing insulation is the key to keeping warm, as well as using windows for solar gain on thermal mass inside the building envelope (not outside as in arid climates). Part of having effective insulation in cold climates is an air-tight envelope, avoiding infiltration. This Finnish cabin has very few and very small windows except on the south side, to maximize solar gain while minimizing losses elsewhere. Before modern insulation, thick solid log walls such as these provided better insulation than board walls could, the whole goal is to collect and preserve heat inside the building as not to lose the warmth to the colder outside environment It’s important to understand Heat Energy Flows in a building to understand insulation. Insulation primarily is designed to prevent heat transfer from conduction and radiation. Resistance to conduction is measured by R-value (high thermal resistance = high R-value) Resistance to radiative heat transfer is measured by emissivity (high resistance = low emissivity and high reflectance). Conduction is the dominant factor when materials are touching each other; when there is an air gap between materials, radiation becomes important. Convection usually only becomes an issue when significant air pockets are involved. Materials used for insulation fall into two broad categories: 1) Fibrous or cellular products – These resist conduction and can be either inorganic (such as glass, rock wool, slag wool, perlite, or vermiculite) or organic (such as cotton, synthetic fibers, cork, foamed rubber, or polystyrene). 2) Metallic or metalized organic reflective membranes - These block radiation heat transfer and must face an air space to be effective.
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3.4.5 Insulation Materials Insulation Materials although insulation can be made from a variety of materials, it usually comes in five physical forms: batting, blown-in, loose-fill, rigid foam board, and reflective films. Each type is made to fit a particular part of a building.
Batting / Blankets
Blown-in/ Loose-Fill
Foamed in Place
3.4.6 Mixed Cold / Hot Climate Envelope Many “temperate� inland climates actually have two extremes--cold in winter, hot and humid in summer. Flexibility is the key to designing for these climates. The Aldo Leopold Center in Wisconsin, first building to be LEED certified as carbon-neutral, uses deep overhangs to allow low winter sun in through the windows to heat up a high-mass concrete slab inside, while blocking high summer sun. It also uses a light roof and darker walls to repel summer sun but absorb winter sun. Extra insulation retains heat in winter, but operable windows passively cool it in summer
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3.5 Passive Cooling 3.5.1 Importance of passive cooling and definition Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or nil energy consumption. This approach works either by preventing heat from entering the interior (heat gain prevention) or by removing heat from the building (natural cooling). Natural cooling utilizes on-site energy, available from the natural environment, combined with the architectural design of building components, rather than mechanical systems to dissipate heat. Therefore, natural cooling depends not only on the architectural design of the building but how it uses the local site natural resources as heat sinks (i.e. everything that absorbs or dissipates heat). Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil.
3.5.2 Modulation and heat dissipation techniques The modulation and heat dissipation techniques rely on natural heat sinks to store and remove the internal heat gains. Examples of natural sinks are night sky, earth soil, and building mass. Therefore passive cooling techniques that use heat sinks can act to either modulate heat gain with thermal mass or dissipate heat through natural cooling strategies. •
Thermal mass: Heat gain modulation of an indoor space can be achieved by the proper use of the building’s thermal mass as a heat sink. The thermal mass will absorb and store heat during daytime hours and return it to the space at a later time. Thermal mass can be coupled with night ventilation natural cooling strategy if the stored heat that will be delivered to the space during the evening/night is not desirable.
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Natural cooling: Natural cooling refers to the use of ventilation or natural heat sinks for heat dissipation from indoor spaces. Natural cooling can be separated into cooling and ventilation, radiative cooling, evaporative cooling, and earth coupling. 25
3.5.3 Ventilation Ventilation as a natural cooling strategy uses the physical properties of air to remove heat or provide cooling to occupants. In select cases, ventilation can be used to cool the building structure, which subsequently may serve as a heat sink. •
Cross ventilation: The strategy of cross ventilation relies on wind to pass through the building for the purpose of cooling the occupants. Cross ventilation requires openings on two sides of the space, called the inlet and outlet. The sizing and placement of the ventilation inlets and outlets will determine the direction and velocity of cross ventilation through the building. Generally, an equal (or greater) area of outlet openings must also be provided to provide adequate cross ventilation.
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Stack ventilation: Cross ventilation is an effective cooling strategy, however, wind is an unreliable resource. Stack ventilation is an alternative design strategy that relies on the buoyancy of warm air to rise and exit through openings located at ceiling height. Cooler outside area replaces the rising warm air through carefully designed inlets placed near the floor.
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Night flush cooling: The building structure acts as a sink through the day and absorbs internal heat gains and solar radiation. Heat can be dissipated from the structure by convective heat loss by allowing cooler air to pass through the building at night. The flow of outdoor air can be induced naturally or mechanically. The next day, the building will perform as a heat sink, maintaining indoor temperatures below the outdoor temperature. This strategy is most effective in climates with a large diurnal swing so the typical maximum indoor temperature is below the outdoor maximum temperature during the hottest months. Thermal mass is a necessary component to dissipate heat at night.
3.5.4 Radiative cooling All objects constantly emit and absorb radiant energy. An object will cool by radiation if the net flow is outward, which is the case during the night. At night, the long-wave radiation from the clear sky is less than the long-wave infrared radiation emitted from a building, thus there is a net 26
flow to the sky. Since the roof provides the greatest surface visible to the night sky, designing the roof to act as a radiator is an effective strategy. There are two types of radiative cooling strategies that utilize the roof surface: direct and indirect. •
Direct radiant cooling: In a building designed to optimize direct radiation cooling, the building roof acts as a heat sink to absorb the daily internal loads. The roof acts as the best heat sink because it is the greatest surface exposed to the night sky. Radiate heat transfer with the night sky will remove heat from the building roof, thus cooling the building structure. Roof ponds are an example of this strategy. The roof pond design became popular with the development of the Sky thermal system designed by Harold Hay in 1977. There are various designs and configurations for the roof pond system but the concept is the same for all designs. The roof uses water, either plastic bags filled with water or an open pond, as the heat sink while a system of movable insulation panels regulate the mode of heating or cooling. During daytime in the summer, the water on the roof is protected from the solar radiation and ambient air temperature by movable insulation, which allows it to serve as a heat sink and absorb, though the ceiling, the heat generated inside. At night, the panels are retracted to allow nocturnal radiation between the roof pond and the night sky, thus removing the stored heat from the day’s internal loads. In winter, the process is reversed so that the roof pond is allowed to absorb solar radiation during the day and release it during the night into the space below.
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Indirect radiant cooling: A heat transfer fluid removes heat from the building structure through radiate heat transfer with the night sky. A common design for this strategy involves a plenum between the building roof and the radiator surface. Air is drawn into the building through the plenum, cooled from the radiator, and cools the mass of the building structure. During the day, the building mass acts as a heat sink.
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3.5.5 Evaporative cooling The design relies on the evaporative process of water to cool the incoming air while simultaneously increasing the relative humidity. A saturated filter is placed at the supply inlet so the natural process of evaporation can cool the supply air. Apart from the energy to drive the fans, water is the only other resource required to provide conditioning to indoor spaces. The effectiveness of evaporative cooling is largely dependent on the humidity of the outside air; dryer air produces more cooling. A study of field performance results in Kuwait revealed that power requirements for an evaporative cooler are approximately 75% less than the power requirements for a conventional packaged unit air-conditioner. As for interior comfort, a study found that evaporative cooling reduced inside air temperature by 9.6°C compared to outdoor temperature.
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3.6 Natural Ventilation 3.6.1 Importance and description of natural ventilation
Natural
Low cost
Improving Air quality
Healthy
Low Maintenance Low
energy consumption Architecture now aims to maximize natural ventilation in their buildings, almost all historic buildings were naturally ventilated, although many have been compromised by the addition of partition walls and mechanical systems. With an increased awareness of the cost and environmental impacts of energy use, natural ventilation has become increasingly attractive method for reducing energy costs and provide good indoor climate, and maintaining healthy and comfortable climate rather than using mechanical methods, natural ventilation can save 10-30% of total energy consumption. Natural ventilation depend on pressure difference to move fresh air through the building, pressure difference caused by wind and buoyancy effect created by temperature difference and humidity difference, in both cases the amount of ventilation depends on size of openings in the building, openings between rooms are technique to complete the airflow circuit through a building Description Fresh air is required to provide oxygen for respiration and increase thermal comfort, if it’s done correctly it can reduce temperature by 5f
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3.6.2 Wind Driven Ventilation As naturally occurring wind blows across a building, the wind hits the windward wall causing a direct positive pressure. The wind moves around the building and leaves the leeward wall with a negative pressure, also known as a sucking effect. The existing of openings on the windward and leeward walls of the building, fresh air will rush in the windward wall opening and exit the leeward wall opening to balance and relieve the pressures on the windward and leeward walls. Building shape is a decisive factor in bringing ventilation by creating wind pressure that drives the air flow directly inside the building. Other several factors also important in ventilation such as: •
Building form and dimension
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Type, shape size of openings
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Construction methods
3.6.3 Stack Ventilation Buoyancy ventilation can be induced by temperature (known as stack ventilation) or by humidity (known as cool tower). Most commonly used is the stack driven ventilation. For stack ventilation to work properly there must be a temperature difference. As the warm air (usually given off by the occupants and their computers), which is less dense, in the building rises, the cooler air is sucked from the openings below. This is shown in the picture below. 30
Design considerations for stack ventilation •
Inlets should supply air low in the room. Outlets should be located across the room and at high level.
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The vertical distance between the inlet and exhaust openings should take advantage of the stack effect.
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Use skylights or ridge vents.
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The function as fire exits of enclosed staircases should not be compromised if stack ventilation is incorporated into the design.
With stack ventilation, it does not rely on the wind. On hot summer days with no wind, the naturally occurring stack effect can take place with relatively stable air flow. Moreover, because it does not rely on the pressure and direction of the wind, there is a greater control on locating the air intake. However, stack driven ventilation is limited to a lower magnitude than wind driven ventilation. It is also very dependent on the inside and outside temperature differences.
3.6.4 Design Strategies for Natural Ventilation The design for natural ventilation should incorporate maximizing both the wind and stack driven ventilation design concepts as mentioned above. General design considerations include: •
Increase air supply intake by ensuring no outside obstruction (such as vegetation or site objects) nor inside obstruction (such as furniture and interior partition) obstruct inlet openings;
•
Rooms should have inlet and outlet openings located in opposing pressure zones. This can include openings on the windward and leeward walls or on the windward wall and roof;
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•
All occupied spaces should have an inlet and outlet opening in which at least a minimum of one opening should be an operable window to control flow;
•
Inlets should supply air at a location low in the room. Outlets should be located across the room and at a higher level;
•
The long facade of the building and the majority of the openings should be should be directed so that the windward wall is perpendicular to the summer wind;
•
Use skylights or ridge vents. They are very desirable for night time thermal comfort in houses to vent heated/warm air that rises, and allow heat to be radiated into the cold. It is also can be a good outlet for wind driven ventilation;
•
At least 3m allowance for the floor to ceiling.
•
window areas should not be excessive and be protected by exterior shading devices;
•
Design for high thermal capacity and exposed ceilings for night cooling.
•
Reduce the possibility of wall warming by the sun through use of light-colored building exteriors, trees/shrubs to provide shading and evaporative cooling, grass and other groundcover to keep ground temperatures low, and ponds and fountains to enhance evaporative cooling; and
•
Internal loading should be kept low.
Many of the considerations taken above is to either increase the air flow or lower the heat gain so that the natural ventilation can effective cool the spaces in the building. Mechanical cooling and ventilation systems will be used to supplement the natural ventilation. By lowering the heat gains, the less air flow will be required to remove the heat, thus there will be less a need of a mechanical cooling system.
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3.6.5 Example for ventilation Lanchester library Fresh air is supplied to the building using light wells, light wells were placed at the corners of the building, although a central light well, Heat gains from building occupants and computers warm internal air and create the buoyancy forces In winter air is heated by pre heating coils which lie across the base, Cooling in the warm summer months is provided by passive methods. Night time venting is used to cool the exposed thermal mass of the building so that it can absorb heat during warm periods of the following day.
The positioning of the light wells is intended to, maintain fresh air distribution and daylight provision across the deep plan floors. Solar gains are minimized by moveable translucent horizontal blinds at the head of the supply light wells, careful window placement and the use of overhangs and metal shading fins which minimize chances of overheat. Daylight is one of the factors which started to be highly considered in designing any building, daylight cant only replace artificial light and reduce light energy use but also influence heating and cooling loads, availability of natural light is crucial in daylight techniques, although its affected by building location and surrounding climate, daylight in each faรงade is essential as a first step in designing
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3.7 Daylight system 3.7.1 Day light with shading: It depends on skylights and ignoring direct sunlight, solar shading system such as pulldown shades reduce daylight access to the room, to increase the daylight while providing shading advanced systems were used such as: Prismatic panels Anidolic zenithal opening=
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Transparent shading system based on total reflection
3.7.2 Daylight system without shading included: Designed to redirect sunlight to areas faraway from windows or skylight openings, it’s divided into 4 categories: •
Diffuse light guiding system
•
Direct light guiding system
•
Diffusing system
•
Light transport system
Some daylight system without shading techniques: Light shelf
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Fish system
3.7.3 Case study: Anz bank The architect tried to maximize daylight in the building, so he decided to design the building around central atrium which was effectively functional because it reduced energy consumption and increased daylight inside the building which also supply healthy environment
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References:
http://www.ecbcs.org/docs/ECBCS_Annex_29_PSR.pdf http://www.breathingbuildings.com/products/natural-ventilation-explained http://www.wbdg.org/resources/naturalventilation.php
References Santamouris, M.; Asimakoupolos, D. (1996). Passive cooling of buildings (1st ed.). 35-37 William Road, London NW1 3ER, UK: James & James (Science Publishers) Ltd. Leo Samuel, D.G.; Shiva Nagendra, S.M.; Maiya, M.P. (August 2013). "Passive alternatives to mechanical air conditioning of building: A review". Building and Environment 66: 54–64. Lechner, Norbert (2009). Heating, Cooling, Lighting: sustainable design methods for architects (3rd ed.). 605 Third Avenue, New York, NY 10158-0012, USA: John Wiley & Sons, Inc.
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Grondzik, Walter T.; Kwok, Alison G.; Stein, Benjamim; Reynolds, John S. (2010). Mechanical and Electrical Equipment For Building (11th ed.). 111 River Street, Hoboken, NJ 07030, USA: John Wiley & Sons. Maheshwari, G.P.; Al-Ragom, F.; Suri, R.K. (May 2001). "Energy-saving potential of an indirect evaporative cooler". Applied Energy 69 (1): 69–76. Amer, E.H. (July 2006). "Passive options for solar cooling of buildings in arid areas". Energy 31 (8-9): 1332–1344. http://www.nachi.org/building-orientation-optimum-energy.htm http://www.architecture.com/RIBA/Aboutus/SustainabilityHub/Designstrategies/Earth/1-1-3-2Buildingorientation.aspx
http://www.asla.org/sustainablelandscapes/cas.html
http://www.verticallandscapes.co.za/benefits.php
http://science.howstuffworks.com/environmental/green-science/green-rooftop.htm http://www.greenroofs.org/index.php/about/aboutgreenwalls
http://inhabitat.com/solar-roadways-smart-parking-lot-harvests-energy-captures-stormwater-and-meltssnow/ http://landarchs.com/solar-panels-paving-way-sustainability/ http://www.greenbuildingadvisor.com/strategies/minimize-buildings-footprint#sthash.gCkYpXkK.dpuf http://iicbe.org/siteadmin/upload/2106C1214074.pdf
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