Building response to sun and sky

1. Climate &
The Built Environment
Unit 2:
Building response to Sun & Sky
MSAJAA-2021A 171022
BUILT ENVIRONMENT - Thermal Comfort
SOURCES OF HEAT GAIN
● Three major sources of unwanted heat-
● Direct solar impacts on a building -
Windows
Skylights
Heat transfer
Infiltration of Exterior high temperatures - Materials & Elements of the structure
Internal heat produced by appliances, equipment & inhabitants
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BUILT ENVIRONMENT - Thermal Comfort
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BUILT ENVIRONMENT - Thermal Comfort
SOURCES OF HEAT GAIN
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2. BUILT ENVIRONMENT - Thermal Comfort
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BUILT ENVIRONMENT - Thermal Comfort
THERMAL COMFORT ZONE
The optimum thermal condition can be defined as the situation in which the
least extra effort is required to maintain the human body’s thermal balance
● Greater the effort that is required, the less comfortable the climate is felt to be
● Maximum comfort condition can usually not be achieved
● Differs somewhat with individuals - depends also on the clothing worn, the
physical activity, age and health condition
● Geographical location plays a role because of habit of individuals
● Can be regulated by HVAC
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BUILT ENVIRONMENT - Thermal Comfort
REGULATING MECHANISM
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BUILT ENVIRONMENT - Thermal Comfort
REGULATING MECHANISM
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3. BUILT ENVIRONMENT - Thermal Comfort
REGULATING MECHANISM
● Temperature difference between
air and surfaces not to exceed 10
- 15°C if comfort is still to be
maintained.
● Range of conditions within which
at least 80% of the people would
feel comfortable is termed as
“comfort zone”
COMFORT ZONE IN DIFFERING AIR AND
SURFACE TEMERATURES
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BUILT ENVIRONMENT - Thermal Comfort
REGULATING MECHANISM
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BUILT ENVIRONMENT - Thermal Comfort
REGULATING MECHANISM
Thermal mass - Measure of a
material to store or retain heat
energy
● High density materials -
Concrete, bricks & tiles-high
thermal mass
● Lightweight materials - Timber &
metal have low thermal mass
● Buildings with high thermal mass
iron have temperature variations
naturally, ranges more consistent
with the ideal human comfort
zone
● Reduced need for artificial
heating and cooling, resulting in
less energy use
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SUN PATH
Seasonal Variations
Refers to the seasonal and Hourly positional change of the Sun and length of
Daylight as Earth rotates and orbits around the Sun
Accurate location and specific knowledge of Sun’s path is essential for-
● Building orientation
● Daylighting
● Summer shading
● Landscaping
● Solar Collector Area for technologies based on solar energy
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4. SUN PATH
Seasonal Variations
● The sun rises in the east and sets
in the west.
● Because the earth rotates on an
axis that is tilted, however, the sun
doesn’t stay exactly in the east or
west.
● In summer, it rises north of east,
travels high across the southern
sky, and sets north of west.
In winter, it rises south of east, travels low across the southern sky, and sets
south of west. How high it gets in the summer and how low in the winter
depend on how far you are from the Equator
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SUN PATH
Seasonal Variations
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SUN PATH
Northern side
● India being in Northern hemisphere - Sun does not touch the North side
at all
● No direct solar radiation from the North - Coolest side with no direct
harsh effects
● Daylight is available for the entire duration of Sun from the North - mostly
remains uniform throughout the duration based on the sky conditions
● Best direction that require ample daylight but no heat gain
● North light is usually used in Industrial Design or Drawing studios
● Courtyards are not preferred in the North as direct sunlight is not
available and hence the diffused radiation is even lower
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SUN PATH
Southern side
● Solar radiation is available in both Summers
& Winters
● In Summers, the Sun angle is high - large
duration of Sun - 14 Hours
● In winters, since the Sun angle is low, lesser
duration of Sun - 9 Hours
● Maximum Solar radiation is only from the
South
● Sufficient daylight during entire duration of
sun-lit hours in Winter
● Summers bring heat and glare and require careful design considerations
● Can be used for living and working areas - bedrooms, kitchens, offices with
adequate heat gain control
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5. SUN PATH
Sun path Diagram
● Solar radiation is available in both Summers
& Winters
● In Summers, the Sun angle is high - large
duration of Sun - 14 Hours
● In winters, since the Sun angle is low, lesser
duration of Sun - 9 Hours
● Maximum Solar radiation is only from the
South
● Sufficient daylight during entire duration of
sun-lit hours in Winter
● Summers bring heat and glare and require
careful design considerations
● Can be used for living and working areas -
bedrooms, kitchens, offices with adequate
heat gain control 17
SUN PATH
Altitude Angle
Solar Altitude Angle (θ) is the vertical angle
at the point of observation, between the
horizon plane and the line connecting the
sun to the observer.
Azimuth Angle
Solar Azimuth Angle (α) is the angle at the
point of observation measured at the
horizontal plane between the north direction
and the vertical plane containing the sun.
Azimuth angle is measured clockwise
from North towards East.
North: (α ) = 0˚ or 360˚
East : (α ) = 90˚
South : (α ) = 180˚
West : (α ) = 270˚
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SUN PATH
Sun path study - Stereographic Diagram
● Convenient way of representing the annual changes in the path of the Sun through the sky on
a single 2D diagram
● Most immediate use is that the solar azimuth and altitude can be read off directly for any time
of the day and month of the year
● Also provide a unique summary of solar position that the architect can refer to when
considering shading requirements and design options.
● There are several methods of projections to present the apparent movement of the sun on
the sky hemisphere. By using any of these projection methods, the apparent
three-dimensional movement of the sun can be represented on a two dimensional chart
which is called SOLAR CHARTS or SUN PATH DIAGRAM.
● Most commonly used projections are EQUIDISTANT and STEREOGRAPHIC Projection
Methods. 19
SUN PATH
Sun path study - Stereographic Diagram
● Sun path diagram prepared by the aid of the
equidistant projection gives easy and direct
reading to the users. On this diagram -
● Circle with 90 mm radius represents the sky
hemisphere on the horizontal plane.
● Center of the circle represents observation
point.
● Perimeter scale gives the azimuth angles (α).
● Concentric circles give the altitude angles (θ).
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6. SUN PATH
Sun path study - Stereographic Diagram
● Group of curves extending from East to West show
the sun path at various dates. The two extreme curves
show sun path in two solstices., June 21 and
December 21. Sun paths for other days lie between
these extremes.
● Vertical radius represent solar noon. Group of curved
lines on both sides of the vertical radius represent
solar hours between sunrise and sunset
● Sunrise and sunset times can be read from the
intersection of sun path curve and the peripheral
circle.
● On equinox days, March 21 and September 21, the
sun rises at 6:00 am & sets at 6:00 pm. In summer,
the sun rises earlier and sets later, in winter it rises
late and sets earlier. 21
SUN PATH
Sun path study - Stereographic Diagram
Steps to read the Sun position from a stereographic sun-path
diagram-
Step 1 - Locate the required hour line on the diagram.
Step 2 - Locate the required date line, remembering that solid
are used for Jan-Jun and dotted lines for Jul-Dec.
Step 3 - Find the intersection point of the hour and date lines.
Remember to look for the intersection of the dotted with
dotted lines.
Step 4 - Draw a line from the very centre of the diagram,
through the intersection of the circle around from the
intersection point to the vertical North axis, on which is
displayed the altitude angles
Step 5 - Read the azimuth as an angle taken clockwise from
North. In this case, the value is about 62°
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SUN PATH
Sun path study - Stereographic Diagram
Step 6 - Trace a concentric “C”
Step 7 - Interpolate between the concentric circle lines to find
the intersection point sits exactly on the 30° line.
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SHADING DEVICES
Any device, external or internal that shades the opening of a built space by
casting its shadow on the same can be termed as a Shading Device 24

7. SHADING DEVICES
Why are Shading devices needed?
● Impact of Solar radiation entering a room through windows
● Increase in air temperature by radiation absorbed on room surfaces
● Increase in the mean radiant temperature of occupants
● High intensities of radiation from direct sun can cause discomfort glare.
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SHADING DEVICES
Functions of Shading devices
● Stop solar radiation penetration into the building during hot periods.
● Allow solar radiation penetration into the building during cool periods.
● Should allow view to the outside from inside the building.
● Should allow daylight into the building.
● Provide some privacy whenever required.
● Protect the occupants of the building from glare.
● Should not interfere with air circulation through the windows.
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SHADING DEVICES
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SHADING DEVICES
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8. SHADING DEVICES
Shadow Angle Protractor:
● The shadow angle protractor gives a
representation of the shadow angles on a
horizontal plan in stereographic projection
and to the same scale as the sun path
diagram.
● Semi-circular protractor, shows two sets of
lines-
- Radial lines marked 0 at centre to -90 to the left and +90 to the right, to give readings of
the horizontal shadow angle
- Arcual lines coincide with the altitude circles along the centreline, but then deviate and
converge at two corners of the protractor. These will give readings of the vertical
shadow angle
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SHADING DEVICES
Performance Parameters of Shading devices
● Thermal performance
● Visual performance
● Acoustic performance
● Aesthetic performance
Values of these parameters depend on -
Independent variables
Climate
Site
Building type
Dependent variables
Heat transfer
Facade type
Position of the blinds relative to the window
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SHADING DEVICES - Types of Vertical Devices
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SHADING DEVICES - Types of Horizontal Devices
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9. SHADING DEVICES - Types of Compound Devices
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SHADING DEVICES - Other types of H & V Devices
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SHADING DEVICES - Design considerations
For an OVERHANG design-
h = D x Tan (Solar altitude) / cos (Solar azimuth – Window azimuth)
For total shade at your target month/hour, set h to height of window from sill to
head and solve for D, required overhang depth.
For partial shade, set h to acceptable height of shadow (perhaps 2/3 of window
height) and solve for D, required overhang depth.
With a given overhang, set D to its depth and find h, the height of shadow it will
cast at your target month/ hour.
For a FIN design-
w = D x Tan (Solar azimuth - Window azimuth)
Solve for either W - width of shadow, or D - depth of fin, as with the overhang equation
Be sure to observe proper signs
If both solar and window azimuths are on the same side of the south vector, then both
values are positive.
If they are on opposite sides of south, then set one azimuth as negative.
Solar azimuth - (-Window azimuth) = Solar azimuth + Window azimuth 35
SHADING DEVICES - Design considerations
Factor method
The following equation provides a quick
method for determining the projection of a
fixed overhang
Projection = Window opening (height) / F
F Factor from the table
Select a factor according to the latitude. The
higher values will provide 100% shading at
noon on June 21st, the lower values until
August 1
North latitude F factor
28 5.5 – 11.1
32 4.0- 6.3
36 3.0- 4.5
40 2.5- 3.4
44 2.0- 2.7
48 1.7- 2.2
52 1.5- 1.8
56 1.3- 1.5
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10. SHADING DEVICES - Design considerations
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DAYLIGHTING
● Practice of placing windows, skylights, other openings and reflective surfaces so that
Sunlight - both direct & indirect can provide effective internal lighting for a built space.
● Special attention is given to daylighting while designing a building when the aim is to
maximize visual comfort or to reduce energy use.
● Energy savings can be achieved from the reduced use of artificial lighting or from passive
heating
Sources
● Primary source is the Sun
● Light received from Sun is through direct solar illumination and Designmethods to enhance
the light reception
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DAYLIGHTING
Why Daylighting?
● Improved Aesthetics of interiors
● Daylight has direct impact on User health - increasing
productivity and maintaining circadian rhythm
● Humans need it for visual and psychological health
● Is a free resource and essential for human survival
● Reduces lighting and HVAC dependence thereby reducing
electricity costs also
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DAYLIGHTING
National Lighting Code
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11. DAYLIGHTING
National Lighting Code
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DAYLIGHTING
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DAYLIGHTING
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DAYLIGHTING
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12. DAYLIGHTING
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DAYLIGHTING
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DAYLIGHTING
Building Massing
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DAYLIGHTING
Building Orientation
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13. DAYLIGHTING
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Overhead Daylighting
Skylights - Domed, horizontal or slightly sling glazed openings in the roof
Clerestories - Usually situated ata a high level ( near the ceiling of the room) -
always above eye level. They provide an effective source of natural light an
ventilation while reducing glare
DAYLIGHTING
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