Passive design strategies use ambient energy sources instead of purchased energy. Microclimates are affected by topography, soil, water, vegetation, and artificial structures. The macroclimate of a larger region influences building design, while microclimates are more localized climates impacted by a building's site conditions. Factors like land form, water bodies, and vegetation type and patterns can impact microclimates and should be considered in building design.

1. Ar.Anand Godson M.Arch (ID)
PASSIVE DESIGN
FACTORS AFFECTS MICROCLIMATE
PASSIVE DESIGN STRATEGIES
Passive design strategies use ambient energy sources instead of purchased energy like
electricity or natural gas. These strategies include daylighting, natural ventilation, and solar
energy. Active design strategies use purchased energy to keep the building comfortable.
SOLAR PASSIVE TECH
Site condition occupy an important position
Careful selection of the site can help save considerable amount of energy and also
provide a fairly satisfactory indoor environment throughout the year.
Micro climate and Macro climate
In the built environment we are generally
concerned with local climatic systems in
particular:
Macro-climate the climate of a larger
area such as a region or a country
Micro-climate the variations
in localised climate around a building
The macro and micro climate has a very
important effect on both the energy
performance and environmental performance
of buildings, both in the heating season and
in summer.
MICROCLIMATE
Microclimate, any climatic condition in a relatively small area, within a few meters or
less above and below the Earth’s surface and within canopies of vegetation. The term usually
applies to the surfaces of terrestrial and glaciated environments, but it could also pertain to the
surfaces of oceans and other bodies of water.
A local atmosphericwhere the climate differs from the surrounding area.
The site of a building may have a many micro climates caused by the presence of hills valleys,
slopes, streams and other buildings. The term may refer to areas as small as a few square feet or
as large as many square miles.
The strongest gradients of temperature and humidity occur just above and below the
terrestrial surface. Complexities of microclimate are necessary for the existence of a variety of
life forms because, although any single species may tolerate only a limited range of climate,

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strongly contrasting microclimates in close proximity provide a total environment in which many
species of flora and fauna can coexist and interact.
Microclimatic conditions depend on such factors as temperature, humidity, wind and
turbulence, dew, frost, heat balance, and evaporation. The effect of soil type on microclimates is
considerable. Sandy soils and other coarse, loose, and dry soils, for example, are subject to high
maximum and low minimum surface temperatures.
The conditions that matter both for the transfer of energy through the building fabric
and for determining the thermal sensation of people are very much site specific local ones.
These generally grouped under the heading of microclimate are the conditions of the
wind, sun radiation, temperature and humidity experienced at particular locations around a
building
The building itself causing a bluff obstruction to the wind flow and casting shadows on
the ground and other buildings, will change its microclimate by its presence.
5 Factors That Affect Microclimates
1. Topography
2. Soil
3. Water
4. Vegetation
5. Artificial Structures
TOPOGRAPHY
The shape of the land is a significant influence on microclimates. While on a large scale,
weather systems have a certain predictability (related to the rotation of the earth and the interplay
between ocean and land), these patterns can get disrupted at the local level by topographical
features such as aspect and slope.
Aspect refers to the direction that a slope faces. This will determine how much solar
radiation it receives, which in turn impacts upon temperature and shading. In the northern
hemisphere south-facing slopes are exposed to more direct sunlight than opposite slopes, as are
north-facing slopes in the southern hemisphere. This will cast longer shadows on the opposite
side of the slope, which must be taken into account when deciding which species of plant to
place there. (This is also the case on flatter ground where trees, hedges, fences and walls cast
shadows.) Even small dips and indentations on your property can affect the microclimate, as they
can form collection points for cold air and as a result sometimes form frost pockets.
SOIL
The composition of the soil affects microclimates primarily through how much water it
retains or which evaporates from it. A soil that has a large proportion of clay retains more
moisture than one that is predominantly sand. The degree to which a soil retains moisture affects

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the humidity and temperature of the air above it. After heavy rains, the soil can contain a lot of
water and modify microclimates much like a body of water such as a lake.
Besides the mineral composition of the soil, the degree of coverage it has will affect
temperature and moisture evaporation. Bare soils reflect more light and heat than those covered
by plants or mulch.
VEGETATION
The vegetation on a permaculture site interacts with the soil and water to affect the
microclimate. Not only does it cover the soil and prevent heat loss and radiation from it, it also
regulates the temperature of the soil, filters dust and other particles from the air, and can act as a
windbreak or suntrap.
Vegetation is naturally adapted to make the most of its climate of origin. So, for instance,
plants that originate in tropical areas tend to have broad, dark leaves that allow for the maximum
absorption of sunlight, and the effective transpiration of moisture back into the air – which will
in turn influence the microclimate in the immediate vicinity. Use native plants in your perm
culture design to make the most of these adaptations.
ARTIFICIAL STRUCTURES
Your house can impact upon microclimates by absorbing heat during the day and
releasing it at night, by deflecting wind and creating sheltered spots, and reflecting sunlight. But
other artificial structures can also play a part in modifying microclimates. For instance, patios
and other paved surfaces like driveways moderate temperature by absorbing and releasing heat,
while fences and walls can give plants protection from wind, shade and shelter from wind. Even
rocks in the garden will have an impact by storing and releasing heat. You can judiciously place
rocks to modify microclimates.
MACROCLIMATE
Macroclimate. : the overall climate of a region usually a large geographic area —distinguished
from microclimate.
The macro climate around a building cannot be affected by any design changes, however the
building design can be developed with a knowledge of the macro climate in which the building is
located.
The knowledge data gives a general impression of the climate at the site of a building and the
building design can be planned accordingly.
However the building itself and surrounding geography will affect the local climate
SITE CONDITION –LAND FORM
LAND FORM
Represents the topographyof the site
It may be flat, undulating or sloping. Major land forms affecting the site are mountains, valley
and plains.
Each of them has varying effect on the microclimate and have to be plannedaccordingly.

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Represents the topographyof the site
It may be flat, undulating or sloping. Major land forms affecting the site are mountains, valley
and plains.
Each of them has varying effect on the microclimate and have to be plannedaccordingly.
VALLEY
The hot air temp being lighter rises above, while cooler air
having higher density settles into the depressions, resulting
in a lower temp at the bottom.
The wind flow is higher along the direction of the valley
than across it due to unrestricted movement
SLOPES
The air speed increases as it moves up the windward side,
reaching a maximum at the crest and minimum on the
leeward side.
The difference in air speed is caused due to the low pressure
area developed on the leeward side.
The orientation of the slope too plays a part in determining
the amount of solar radiation falling on the site.
SITE CONDITION –WATER BODIES
Sea, Lake, River, Pond, Fountain
Water absorbs relatively large amount of radiation. They also allow evaporative cooling. As a
result, during the daytime areas around water bodies are generally cooler. At night, however,
water bodies release relatively large amounts of heat to the surroundings. This heat can be used
for warming purposes.

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In hot-dry climates, water/ water bodies can be used both for evaporative cooling as well as
minimizing heat gain. Taking into account wind patterns and vegetation they can be used to
direct cool breeze into the house. A roof pond minimizes heat gain through the roof.
In cold climates, water bodies are beneficial only if their heat gain and loss can be controlled.
This would happen only if the water body can be enclosed by the building. However, we may be
faced with a large water body in a cold region. The best thing to do then is to stay away from it.
The wind pattern would have to be studied and winds avoided either by building location,
vegetation pattern or both.
In warm-humid regionswater bodies are best avoided. The minimal benefit provided by
evaporative cooling would be offset by the heightened humidity levels.
SITE CONDITION –VEGETATION TYPE AND PATTERN
Important role in changing the microclimate of the place
They absorb radiation for photosynthesis.
Shading a particular part of the structure and ground to reduce the heat gain and reflected
radiation.
By releasing moisture, they help raise the humidity level.
Vegetation creates different air flow patterns and can be used to direct or divert the prevailing
wind advantageously by causing minor pressure differences.
Based on the requirement of a climate, an appropriate type of tree can be selected. Planting
deciduous trees such as mulberry and champa on east and west side would prove beneficial in
HOT DRY Zones.
Besides providing shadefrom intense and glaring morning and evening sun, they also cut off
hot breezes.
Deciduous trees shed their leaves in winter to allow solar radiation to heat the building.
Landscaping is an important element in altering the microclimate of a place. Proper landscaping
reduces direct sun from striking and heating up of 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 advantageously by causing a
pressure difference. Additionally, the shade created by trees and the effect of grass and shrubs
reduce air temperatures adjoining the building and provide evaporative cooling. Properly
designed roof gardens help to reduce heat loads in a building.
A study shows that the ambient air under a tree adjacent to the wall is about 2 °C to 2.5
°C lower than that for unshaded areas, which reduces heat gain by conduction Vegetation should
not be a obstruction of air movement. Vegetation should act as a filtration of wind. They should
act as a guidance of wind flow.

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ROLE OF VEGETATION IN SITE PLANNING
Preservation of Natural Vegetation
The preservation of natural vegetation
during construction provides natural buffer
zones, protects soils from water and wind
erosion, removes sediments and other
pollutants from storm water runoff, and is
aesthetically pleasing. This technique can
be applied to all types of sites.
KEY BENEFITS
Vegetation absorbs the energy of falling rain.
Dense root structures hold soils in place and increase the soil’s absorptive capacity.
Plant roots hold soil particles in place and preserve and promote development of soil structure,
resulting in increased soil permeability which increases the soil’s ability to absorb storm water
runoff.
Vegetation also:
Slows the velocity of runoff and acts as a filter to
trap sediment. Serves as a buffer zone against
noise. Enhances aesthetics of the area.
Provides areas where wildlife can remain
undisturbed. Provides a source of shade during
summer months.

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May add to the value of residential and commercial properties.
Usually requires less maintenance than planting new vegetation.
PLANNING CONSIDERATION
Extremely well-suited for use in areas prone to high rates of soil erosion where other soil
erosion control measures would be difficult to establish, install, or maintain.
Use in areas where it is desirable to reduce storm water runoff sheet flow velocities.
Can be used to protect unique or endangered plant species.
PRESERVATION OF NATURAL VEGETATION
Discussion Soil erosion is a leading cause of water quality problems in Indiana. It
impacts water quality by degrading the habitat of aquatic organisms and fish, promotes the
growth of nuisance weeds and algae, and decreases its recreational value. During construction, if
disturbed land is left unprotected its erosion potential increases, storm water runoff volumes and
sediment loadings increase, and the potential for surface water degradation increases. The
preservation of vegetation should be planned before any site disturbance begins. Planners should
note the locations where vegetation should be preserved and consider this when determining the
location of roads, buildings, or other structures. Highly visible barricades and signs should be
erected to protect vegetation boundaries selected for preservation. Preventing damage is less
costly than correcting it. Planning should include the maintenance requirements of the existing
vegetation. Based on soil types and climate, different species will require different maintenance
activities such as mowing, fertilization, irrigation, pruning, and weed/pest control. These
activities should be performed regularly during construction.

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PRESERVATION & PROTECTION—NATURAL SITE DESIGN
RIPARIAN BUFFER ZONES
Riparian buffer zones are natural
vegetative zones along creeks,
streams, channels, or other water
bodies. They typically consist of
tree, shrub, and grass plantings.
SITE CONDITION –MIRCOCLIMATE STREET WIDTH AND ORIENTATION
The amount of direct radiation received by a building and the street in an urban area is
determined by the street width and its orientation.
Solar radiation can effectively be controlled by modulating them.
Consider this point while designing a large residential complex as well as at the town planning
level.
The building on one side of the street trend to cast a shadow on the street and the opposite
building, if they block the sun’s radiation.
Thus the width of the street can be relatively narrow or wide depending upon whether the solar
radiation is desirable or not.
HOT AND DRY CLIMATE –Jaisalmer
Most of the streets are narrow with building shading each other to reduce the solar radiation
The orientation of the street is particularly useful for controlling air flow.
The streets can be oriented parallel to prevailing wind direction for free air flow.
Smaller streets or pedestrian walkways may have number of turns to modulate wind speed.
For restricting or avoiding wind, the streets may be oriented at an angle normal to the
prevailing wind direction.

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SITE CONDITION –OPEN SPACES AND BUILT FORM / SURFACE TO VOLUME
RATIO
Open spaces and built form are responsible for the different patterns of air flow in and around a
building, affecting heat gain and heat loss.
Both together can modify the micro-climate of the site. Open spaces such as courtyardscan be
designed such that solar radiation incident on them during daytime be reflected on the building
facades for augmenting solar heat. This is desirable in cold climates and possible if the surface
finish of the courtyard is reflective in nature.
Courtyardscan also be designed to act as heat sinks. If it is covered by grass and other
vegetation, it would provide a cooler environment. Water sprayed on the courtyards would cause
cooling effect.
The air in open spaces shaded by surrounding buildings would be coolerand can be used to
facilitate proper ventilation and promote heat loss through building envelope. Built forms can be
such that the buildings cause mutual shading and thus reduce heat gain.
For ensuring unobstructed air flow, taller structures can be plannedtowards the rear side of a
building complex

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SITE CONDITION –SURFACE TO VOLUME RATIO
The volume of space inside a building that needs
to be heated or cooledandits relationship with
the area of the envelope enclosing the volume
affects the thermal performance of the building.
This parameter, known as the S/V (surface-to-
volume) ratio,is determined by the building
form. For any given building volume, the more
compact the shape, the less wasteful it is in
gaining/losing heat.
Hence, in hot, dry, regions and cold climates,
buildings are compact in form with a low S/V
ratio to reduce heat gain and losses respectively. Also, the building form determines the airflow
pattern a round the building, directly affecting its ventilation. The depth of a building also
determines the requirements for artificial lighting -greater more the depth, higher the need for
artificial lighting.
ORIENTATION
Orientation refers to the location of a building with respect to the cardinal directions, (i.e.)
North-South and East-West. Building orientation is an important parameter of design.
In Cold climates, building needs to be orientated such that solar radiation is admitted to the
maximum possible, while reverse is true of hot regions.
For a cold climate, an orientation slightly east of south is
favored (especially 15°east of south), as this exposes the
unit to more morning than afternoon sun and enables the
house to begin to heat during the day.
Similarly winds can be desirable or unwanted,
depending on the climate sometimes a compromise is
required between these two orientations With careful
design, shading and deflecting devices can be
incorporated to exclude thesun or redirect it into the
building, just as wind can be diverted or directed to the
extend desired.

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PLAN FORM AND BUILDING ENVELOPE
The plan form of the building affects the amount of solar radiation received by the building and
the air flow around it. Therefore it plays an important role in ventilation and heat loss or gain.
Wind when obstructed by a building creates pressure differences, i.e. positive pressure on
windward side and negative pressure on the leeward side.
Consequently, a new airflow pattern is established around the building. Appropriate openings
connecting high to low pressure areas provide effective ventilation.