LANDSCAPE TECHNIQUES FOR ENERGY CONSERVATION

Since ancient time humans' entire pattern of life is dependent on the climatic conditions in which they live. By the use of updated technology, humans have tried to modify the climate within the building from outside.
Humans' dependence on nature even in historic times can be realized from the fact that each community and population was built based on the local climate. Today, it is ironic that, human is out of balance with nature.
The use of latest technology should have led to better utilization of the available resources but that is not so. Even most powerful source of energy around him is neglected.
Today the buildings are so designed that they contribute to serious environmental problems because of excessive consumption of energy and other natural resources. This relationship between energy use in building and environmental impairment arises from the fact that energy-intensive solutions adopted in a building to meet its demand for heating, cooling, ventilation and lighting, cause severe depletion of invaluable environmental resources.
Architects can achieve energy efficiency in building by carrying out a study of the macro and micro-climate of the site, applying bioclimatic architecture principles to combat the adverse effects, and taking advantage of the desirable conditions. A few common design elements that directly or indirectly affect thermal conditions and thereby the energy consumption in a building are:

  • Landscaping
  • Ratio to built-form to open spaces
  • Location of water bodies
  • Orientation
  • Plan form
  • Building envelope and fenestration
Landscaping is an important component in altering the micro-climate of a place. Proper landscaping reduces the direct sun ray from striking and heating up building surfaces. It prevents reflected light carrying heat into a building from the ground or other surfaces. Landscaping creates different airflow patterns and can be used to direct or divert the wind favourably by causing pressure difference. Additionally, the shade creates by trees and the effect of grass and shrubs reduce air temperature around the building and provide evaporation cooling. Properly designed roof gardens helps to reduce heat loads in a building. This article deals with the content to which the natural processes, elements and factors can be utilized in landscape architecture for energy conservation. And, also the design-alternatives, which effect the micro-climate by modification in earth forms at all levels, vegetation of all types and water bodies in its various forms. The use or manipulation of these elements or process will eventually result in energy-efficient buildings.

Each of the major climate region has diverse needs to modify the basic climate comfortable for human users. In cooler regions it is necessary to utilize as much heat as possible in order to reduce energy consumption for mechanical heating. In hot climate it is desirable to modify climate to provide cooling. In dry areas existing moisture can be maximized or moisture may have to be introduced by means of natural process in order to make the climate more habitable.

Solar radiation before striking the earth's surface passes through the atmosphere. In this movement a series of obstructions cause a diminution and dissipation of the full impact of the original radiation. A portion of the radiation is reflected back into space, some of it is dissipated within the atmosphere; and portions are diffused throughout the atmosphere. A small portion of the original solar radiation strikes the earth's surface, the vegetation on the earth and buildings as well as man and animals as they move about the earth. Natural elements and water bodies can modify the impact of the incoming solar radiation in a various ways. How much solar radiation strikes the earth surface and how and where it strikes materially affect the micro and macro-climate of that area.

As winds move over the surface of the earth, they encounter a series of obstructions, which detract, deflect, obstruct and lessen the impact or speed of flow of the unobstructed wind.
These obstacles do this in a variety of ways and to a variety of degrees. This is two sided climate effect of natural elements , one: lessening the impact of solar radiation or wind, second: accelerating or enhancing the impact. The climate of an area or of a particular site depends to a large extent on the speed, direction and type of wind in a particular location. The degree to which the climate must be modified in order to bring it within the human comfort range determines the amount of energy which must be utilized or expended in order to make the proximate micro-climate of the individual.

All kinds of natural element affects the climate. The natural elements can be manipulated, altered and shaped in order to control the effective climate more efficiently. The site planner can manipulates the perceived impact of the local climate as it affects people in a single building or group of buildings.

LANDFORMS:

Topography or modulations of earth either in natural undisturbed state or as manipulated by human, has the ability to modify, upgrade or accentuate climatic variations in various ways. The landforms may be:

1. Large Landforms
Mountain range diverts air masses. They affect the flow of moisture-laden air and cause rain shadows for the areas in their lee.
Temperature decreases with the rise in height and cold air flows downhill and settles in valleys.
Airflow pattern vary diurnally in the areas with large variation in landforms.
Impact of topography on climate control
Impact of topography on climate control Impact of topography on climate control
Impact of topography on climate control

2. Smaller Landforms
Smaller landforms can be involved in either solar radiation interception or in wind control through interception, deflection or curtailment. Advantages of smaller landforms are:
Landforms to integrate solar collection device Landforms to integrate solar collection device

Landforms to Improve the Vegetation Landforms to integrate solar collection device

  1. Creation of small landforms in larger ones provide better orientation or site conditions for utilization or interception of solar radiation.
  2. Adjustment in major landforms can be helpful in picking up maximum solar radiation.
  3. Smaller landforms with vegetation have effective climate control.
  4. In hilly areas where sun is necessary but wind needs to be reduced landforms can block unwanted wind or other influences and also provide an area in which the potential radiation for particular area is maximized.
  5. Occasionally, it may be better to locate solar panels away from the building utilizing the solar energy gathered by the collector devices. In such cases landforms may be created or utilized to integrate the solar panels with surrounding landscape.
  6. Sometimes, the solar panels used for solar collection on a building may be odd looking and it may become necessary to resize it by smaller ones, if properly controlled and manipulated can direct wind patterns either towards or away from particular areas.
Vegetation can control the sun's effect by filtration of direct solar radiation in the following ways:
  • By controlling the amount of heat radiated from ground surfaces, by obstruction and control of reflected radiation.
  • And the control of winds by Obstruction, Filtration, Deflection and Guidance.
The use of vegetation for controlling wind is mostly familiar. Vegetation areas designed to fulfil these general needs are usually classified as windbreaks and shelterbelts. The term windbreak denotes to protective planting around a garden or orchard. Windbreaks may also provide shade for buildings or cattle pens, and have aesthetic value in areas, which do not have much existing vegetation cover. Windbreaks generally consist of a single or double row of trees. The term shelterbelt refers to extensive barriers of trees protecting the areas. To be effective, shelterbelts require a much more careful layout than simple windbreak.
Role of Vegetation in Wind Control Role of Vegetation in Wind Control

Role of Vegetation in Wind Control Role of Vegetation in Wind Control

Role of Vegetation in Wind Control Role of Vegetation in Wind Control

Role of Vegetation in Wind Control Role of Vegetation in Wind Control


DESIGN PRINCIPLES OF A SHELTERBELT
The horizontal range of shelterbelt is proportional to the height of the belt.

Permeability
  • The degree of permeability is the percentage ratio of the perforated area of the belt to the total vertical area of the belt.
  • Permeability of shelterbelt to the airflow is the main factor affecting the wind speed on leeward side.
  • Dense shelterbelt causes strong reduction immediately behind the shelterbelt, connected with eddies and turbulence.
  • The distance at which the wind speed is re-established is relatively small.
  • The more impenetrable the belt, the shorter is the distance to the point of reduction in velocity.
  • With 40% - 50% permeability the minimum of wind speed is at a distance equal to 6 times the height.
Surface roughness of soil surface
  • The range of wind reduction increases with the decrease in surface roughness.
Direction
  • The effect is greatest when the wind blows perpendicular to the shelterbelt.
  • With the decrease of angle of incidence, the protected zone decreases. Influence on wind reduction is less for angles of incidence more than 45 degrees.
  • At 45 degrees the extent decreases to 0.25.
  • For wind blowing parallel to the shelterbelt, there is a reduction of height equal to 5 times.
Width of shelterbelt
  • Single row gives limited reduction. Several rows are better.
  • Staggering of the rows are better to break the velocity and this would not create tunneling effect for wind blast.
  • A streamlined or vertical belt provides less protection as compared to the belt with triangular shaped top surface belt. It is suggested the tallest tree in the middle row followed by medium height trees in the side rows and low height trees and bushes in the outer rows.
  • The depth of shelterbelt should be approximately ten times its height. However, this is only a thumb rule. Lesser widths of 20 meters to 30 meters are found to be useful in the particular situations, minimum width being 15 meters.
Spacing of plants
  • Usually single or double row of trees are planted at 0.7m to 1.5m according to the species.
  • Normally, a one-year-old tree sapling is grown.
  • The distance between rows can be 2m to 2.5m and 3m to 4m if tractor is used for cultivation.
  • The crop yield is highest near the belt.

BENEFITS OF SHELTERBELT

On heat and water balance:
  • Radiation is reduced by shelterbelt only in the immediate surrounding.
  • The reduction of potential and actual evapotranspiration and loss of soil moisture by reducing wind speed is the main purpose of shelterbelt.
  • Increase in soil moisture content varies from 3% to 7.8% and low water loss due to evaporation increases the production by 15%.
On wind:
  • Reduction in wind velocity thereby arresting the movements of sand and soil particles.
  • Wind erosion substantially controls the reduction in the wind speed.
On crops and plants:
  • Protection of crops from being blown down by high winds.
  • High wind velocity decreases the stomatal apertures. As photosynthesis depends upon carbon dioxide intake through these apertures, growth of plant may be affected if not protected from high winds.
  • The yield immediately behind the belt is less due to the competition from roots of trees and bushes.
The suggested species for shelterbelt:
  • Tall trees: Azadirachta indica, Albizia, lebbek, Albizia amara, Acacia tortilis, Dalbergia sissoo.
  • Medium sized trees: Acacia nilotica, Acacia senegal, Cassia siamea, Prosopis cineraria, Hardwicke binnata, Tamarix articulata, Anogeissus pendula, Tecomella undulata.
  • Taller shrubs: Prosopis juliflora, Parkinsonia aculeata, Acacia aneura, Dichrostachys nutans, Colophospermum mopane.
  • Small shrubs: Zizyphus nummularia, Capparis deciduas, Calligonum polygonoides, Cassia auriculata, Leptadenia pyrotechnica, Atriplex nummularia, Chenopodium auricomum.

These trees not only control the precipitation but also control the seasonal and annual temperature variations. The effectiveness of specific plant in climate control depends upon the type and character of plant, the climate of the region and the specific requirements of the site. Vegetation may absorb over 90% of sun light falling upon it, reduce wind speeds in an area to less than 10% of that in the open, increase or reduce day time temperature by as much as 15 degrees and sometimes increase night temperature.
Summarizing, the principal uses of vegetation to the energy conscious designs are:
  • Large and small trees and shrubs to screen out undesirable winds.
  • Trees may be used to channel wind to increase ventilation in specific areas.
  • Planting will reduce the accumulation of snow on the ground and may be used to safeguard the solar panels.
  • Deciduous trees will screen out direct sunlight during the summers, to reduce essential cooling loads, but allow it to bypass through in the winters, reducing required heating loads.
  • Planted areas will be cooler during the day and experience less heat loss at night.

WATER


Impact of Water on Climate Control


Impact of Water on Climate Control Impact of Water on Climate Control

Water has great impact on climate control, especially in the utilization of solar radiation and energy conservation. Water stores large percentage of insolation striking the water surface and a small percentage is radiated off. At the same time, while a small percentage of the solar energy strikes the land surface a large percentage of the same energy is radiated back into the atmosphere.
Wind flows from the water body onto the shore during the day and vice versa at night. This natural airflow pattern may be utilized and controlled for natural ventilation.

Impact of Water on Climate Control
The leeward side of the water body will always be cooler since the wind is cooled as it moves across the surface of the water body. So, it is necessary that areas or activities, which need to be naturally cool, should be located on leeward side of the water bodies and functions or areas, which need extra heat or warmth, on the windward side of the water body.





***LANDSCAPE TECHNIQUES FOR ENERGY CONSERVATION ***



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Green Environment

Hi, I’m Gobinda Burman (Green Environment). More than 27 years in the field of Building Construction industry, I’ve completed many high-rise building projects successfully. I have got the opportunity to learn and solve the critical practical problems related to building construction. I love to share my knowledge with those people who wants to build their own home and the budding civil engineers willing to build their career in this field..

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