In the built environment we are generally
concerned with local climatic systems in particular:
1. Macro-climate the climate of a larger area such as a
region or a country
2. 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.
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
General climatic data give an idea of the local
Seasonal accumulated temperature difference
(degree day) - a measure of the outside air temperature,
though do not account for available solar
Typical wind speeds and direction
Annual totals of Global Horizontal Solar Radiation
The Driving Rain Index (DRI) - the amount of moisture
contained in exposed surfaces and will affect thermal
conductivity of external surfaces.
Assumption of climate for a large project that
covering extensive area.
On small sites, where there is less scope for
variations in siting and orientation, this exercise
will be more limited, but some consideration of
local climatic patterns will always be justified.
A local atmospheric where 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.
Factors Influencing Micro Climate
1. Solar Access
Minimising solar overheating in summer
while maximising solar access during the winter.
Buildings with a heating requirement should be orientated
north south with maximum glazing on the south face.
Trees offer an excellent means of site shading
The colour of surrounding surfaces will have an effect on
the solar radiation available to the building.
Grass planted outside a building will reduce the ground
Use of courtyards and water can also moderate the
effects of high temperatures on summer. 10
Factors Influencing Micro Climate
2. Wind Control
Avoidance of funnel-like gaps between buildings
Avoidance of flat roofed buildings and cubical forms
Avoid abrupt changes in building heights
Orientate long axis of the building parallel to the direction of
Use podium to limit down draught at ground level
Groups of buildings can be arranged inirregular patterns to
avoid wind tunneling.
Coniferous trees and fencing and other landscape features
(mounds of earth and hedges) - reduce the impact of wind
and driving rain on the building structure. 11
Factors which may cause local deviation are:-
The factors causing deviations of urban climate:
1.Changed surface qualities (pavements and
buildings) – increased absorbance of solar radiation;
2.Buildings – casting a shadow and acting as barriers
to winds, channeling the wind by increase in velocity
3. Energy seepage – through wall and ventilation of
4. Atmospheric pollution – waste products, smoke
from motorcars, fumes and vapors
Level of Deviation
1. Air temperature – a city will have a higher
temperature than the surrounding countryside –
11°C has been reported
2. Relative humidity – reduced by 5-10% - quick
run-off rainwater, absence of vegetation, higher
3. Wind velocity – reduced to less than half of that in
the adjoining open country
What are the differences between
MACRO & MICRO CLIMATE?