climatology

1. 1. Passive Solar Design
 Passive solar design refers to the use of the sun’s energy for the heating and cooling of living
spaces by exposure to the sun.
 When sunlight strikes a building, the building materials can reflect, transmit, or absorb the solar
radiation. In addition, the heat produced by the sun causes air movement that can be predictable in
designed spaces.
 These basic responses to solar heat lead to design elements, material choices and placements that
can provide heating and cooling effects in a home.
 Unlike active solar heating systems, passive systems are simple and do not involve substantial use
of mechanical and electrical devices, such as pumps, fans, or electrical controls to move the solar
energy.
Image: 1 COMPARATIVE DIAGRAM ACTIVE / PASSIVE DESIGN
1.1 Passive Solar Design principles:
 Aperture/Collector: The large glass area through which sunlight enters the building. It should not be
shaded by other buildings or trees generally from 9a.m. to 3p.m. during the day time when sun has the
maximum heat.
 Absorber: The hard, darkened surface of the storage element which absorb the sunlight as heat. It
could be a masonry wall, floor, or a water container which is exposed directly to sunlight.
 Thermal mass: Materials that retain or store the heat produced by sunlight. The thermal mass is the
material below and behind the absorber surface.
 Distribution: Method by which solar heat circulates from the collector to different areas of the house.
There are 3 natural heat transfer modes in passive solar design - conduction, convection and
radiation. In some active solar systems, fans, ducts and blowers are also used to distribute the heat.

2.  Control: the elements that are used to shade the building in summer; generally roof overhangs are use
as control.
2. Passive Solar Heating
 The goal of passive solar heating systems is to capture the sun’s heat within the building’s elements
and to release that heat during periods when the sun is absent, while also maintaining a
comfortable room temperature.
 The two primary elements of passive solar heating are south facing glass walls and thermal
mass to absorb, store, and distribute heat.
 There are several different approaches to implementing those elements.
2.1 Direct Gain:
Direct gain is the simplest passive solar home design technique. Sunlight enters the house through the
aperture (collector)—usually south-facing windows with a glazing material made of transparent or
translucent glass. The sunlight then strikes masonry floors and/or walls, which absorb and store the solar
heat. The surfaces of these masonry floors and walls are typically a dark color because dark colors usually
absorb more heat than light colors. At night, as the room cools, the heat stored in the thermal mass
convects and radiates into the room. The amount of passive solar depends on the area of glazing and the
amount of thermal mass. The glazing area determines how much solar heat can be collected. And the
amount of thermal mass determines how much of that heat can be stored.
2.1.1 Design strategies to maximize the heat gain:
1. Site analysis – understand the climate of site on which building is to be located.

3. 2. Massing - use a basic massing of the building layout to determine specifically on site the most
optimal location for the building to be situated.
3. Select the appropriate window areas and glazing types based on orientation.
4. Design to allow natural ventilation.
5. A heat load analysis of the house should be conducted.
6. Use a medium dark color for masonry floors; use light colors for other lightweight walls;
thermal mass walls can be any color.
7. Fill the cavities of any concrete block used as thermal storage with concrete or other high mass
substance.
8. Use thermal mass at less thickness throughout the living space rather than a concentrated area of
thicker mass.
2.2 Indirect Gain
Indirect gain uses the same material and design principles as direct gain systems. The Thermal mass is
located between the sun and the living space. It absorbs the sunlight that strikes to its surface and
transfers it to the living space by conduction. The indirect gain system utilizes 30-45% of the sun’s energy
striking the thermal mass. The sun’s heat is collected and trapped in narrow space between the window
and the thermal mass. The heated air rises up and entres into the room through vents at the top of the wall
and circulates in room by convection. The thermal mass continues to absorb and store heat to radiate back
into the room in absense of sun. Cooled air moves to take its place from vents at bottom of the wall.
2.2.1. Thermal storage wall systems:
Trombe wall
Water wall
Trans wall
2.2.2 Trombe wall :
The most common indirect gain systems are a Trombe wall. The thermal mass in form of thick masonry
wall, is located immediately behind south facing glass of single or double layer. Solar heat is absorbed by
the wall’s dark-colored outside surface and stored in the wall’s mass, where it radiates into the living space.
Operable vents at the top and bottom of a thermal storage wall permit heat to convect between the wall
and the glass into the living space. When the vents are closed at night, radiant heat from the wall heats the
living space.

4. 2.2.3 Design principles for trombe wall :
1. The exterior of the mass wall (toward the sun) should be a dark color.
2. Use a minimum space of 4 inches between the thermal mass wall and the glass.
3. Vents used in a thermal mass wall must be closed at night.
4. Thermal wall thickness should be approximately 10-14 inches for brick, 12-18 inches for concrete.
2.2.4 Types of trombe wall :
1) Non vented:
1. The heat energy is store during day time , radiated and conducted during living space
2. No direct convection of air between air gap & living space.
3. Suitable for residence as thermal storages is required for night heating.
4. Does not help ventilation in summer.
2) Vented :
1. Vents on the upper and lower side of the wall provide the direct convection between air gap & living
space increases the heat transfer in day times.
2. Most suitable for office as working hours during day times will get efficient heating.
3. Help natural ventilation in summer.
2.3. Roof pond systems:
Six to twelve inches of water are contained on a flat roof. This system is best for cooling in low humidity
climates but can be modified to work in high humidity climates. Water is usually stored in large plastic or
fiberglass containers covered by glazing and the space below is warmed by radiant heat from the warm
water above.

5. 2.4 Solar chimney:
Solar chimneys are systems of natural ventilation that use solar radiation to produce convective currents.
The convective currents draw the air inside of the building requiring one or more solar chimneys to allow an
enough heat income from the solar radiation to create the thermal effect. As a result, an air temperature
difference is created and a density gradient between the inside and the outside of the chimney is obtained,
which induces a natural upwards movement of air. The impact of the air movement decreases the
temperature inside the house.
2.5 Isolated Gain :
Isolated gain systems collect solar energy in a location separate from the space desired to
be heated. There are multiple types of isolated gain systems , sunspaces are the most common system.
A sunspace is a room designed to capture heat. Vertical windows capture the heat just like the
direct and indirect gain system. The same masonry walls or water drums are used as thermal mass.
Distribution is achieved through ceiling and floor vents, windows/doors. The sunspace is often separated
by the rest of the home using windows or doors. This protects the home against the sun’s changing
temperatures.
.

6. 2.6 Trans wall :
It is the combination of a direct gain and thermal storage. It partially absorbs and partially transmits the
solar radiation. It consists of a transparent modular water wall which plays an aesthetic role by providing
visual access to the building interior. This wall is build on a metal frame that holds a water container
constructed from glass walls and a semi transparent absorbing plate that is positioned between the walls.
3. Passive Solar Cooling
Passive cooling systems are least expensive means of cooling a home which maximizes the efficiency of
the building without any use of mechanical devices. It relies on the natural heat sinks to remove heat from
building. They achieve cooling from evaporation, convection and radiation without using any mechanical
device. It depends on daily changes in temperature and humidity.
3.1. Design strategies for passive cooling:
1. Natural ventilation
2. Shading
3. Wind towers
4. Earth sheltering
5. Evaporative cooling
6. Earth air tunnels
7. Thermal mass
3.1.1. Natural ventilation:
Windows play an important role for good ventilation. Good ventilation will reduce the heat load on
mechanical devices. In order to have a good ventilation, windows should be placed according to the
climatic zones. (Refer climate responsive designs)
Natural ventilation maintains an indoor temperature that is close to the outdoor temperature, so it’s only an
effective cooling technique when the indoor temperature is equal to or higher than the outdoor one. The
climate determines the best natural ventilation strategy.

7. 3.1.2. Shading:
The most effective way of cooling a building is to shade windows, walls and roof of building from direct
solar radiation. By shading a building and its outdoor spaces we can reduce summer temperatures,
improve comfort and save energy. A variety of shading techniques are used such as fixed or adjustable
shade; trees and vegetation, depending on the building’s orientation as well as climate and latitude.
3.1.3. Wind towers:
Wind tower is a key element in traditional architecture settlements in hot, hot-dry and hot-humid climates.
they are vertical shafts with vents on top to lead desired wind to the interior spaces and provide thermal
comfort. This architectural element shows the compatibility of architectural design with natural environment.
It conserves energy and functions on the basis of sustainability principles.
A wind tower is an architectural device used for many centuries to create natural ventilation in buildings.
The function of a wind tower is to catch cooler breeze that prevail at a higher level above the ground and to
direct it into the interior of the buildings
wind towers come in various designs, such as the uni-directional, bi-directional, and multi-directional.

8. 3.1.4. Earth sheltering:
Earth sheltering is a means of using earth to effectively shelter an architectural structure, reducing its heat
loss and helping to maintain a steady indoor temperature.
Two types of earth sheltering:
1. Underground which means the entire house is built below grade and
2. Bermed which is built either above ground or partially below and with earth covering one or
more walls.
3.1.5. Evaporative cooling
It lowers the indoor air temperature by evaporating water. It is effective in hot and dry climate where
humidity is low. The heat of air is used to evaporate water, thereby cooling the air which in turn cools
the living space of building. Increase in contact between water and air increases the rate of
evaporation. The pond, lake or sea near the building or fountain in a courtyard can provide a cooling
effect.

9. 3.1.6. Earth air tunnels:
At a depth of 4 m below ground, the temperature inside the earth remains nearly constant and is nearly to
the annual average temperature of a place. This temperature is capture through a tunnel in the form of
pipe. The air in the tunnel will get cooled in summer and warmed in winter. This air cab ne used for cooling
in summer and heating in winter.
3.1.7. Thermal Mass:
Thermal mass is the ability of a material to absorb and store heat energy. A lot of heat energy is required to
change the temperature of high density materials like concrete, bricks and tiles. They are therefore said to
have high thermal mass. Lightweight materials such as timber have low thermal mass. Thermal mass can
store solar energy during the day and re-radiate it at night.

10. Thermal mass acts as a thermal battery. During summer it absorbs heat during the day and releases it by
night to cooling breezes or clear night skies, keeping the house comfortable. In winter the same thermal
mass can store the heat from the sun or heaters to release it at night, helping the home stay warm.
Thermal mass is not a substitute for insulation. Thermal mass stores and re-releases heat whereas
insulation stops heat flowing into or out of the building. Thermal mass is particularly beneficial where there
is a big difference between day and night outdoor temperatures.