Climatology - Passive Solar Designateeee

Climatology- architecture

1. T. HIMA SRI
SEMIII
SECTIONA
22041AA028

2. Passive solar design refers to the use of the
sun’s energyfor the heating and
coolingof living spaces by exposure to the
sun. When sunlight strikes a building, the
building materials can reflect, transmit, or
absorbthe 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 simpleand do not involve
substantial use of mechanicaland
electrical devices, such as pumps, fans,
or electrical controls to move the solar energy.

3. Five elements of Passive Solar Design
•Aperture/Collector: The
large glass area through which
sunlight enters the building. The
aperture(s) should face within 30
degrees of true south and should
not be shaded by other buildings
or trees from 9a.m. to 3p.m. daily
during the heating season.
•Absorber:The hard, darkened
surface of the storage element.
The surface, which could be a
masonry wall, floor, or water
container, sits in the direct path
of sunlight. Sunlight hitting the
surface is absorbed as heat.

4. •Thermal mass:Materials that retain or store the heat produced by sunlight. While the absorber is an exposed
surface, the thermal mass is the material below and behind this surface.
•Distribution:Method by which solar heat circulates from the collection and storage points to different areas of
the house. A strictly passive design will use the three natural heat transfer modes-conduction, convection and
radiation-exclusively. In some applications, fans, ducts and blowers may be used to distribute the heat through the
house.
•Control:Roof overhangs can be used to shade the aperture area during summer months. Other elements that
control under and/or overheating include electronic sensing devices, such as a differential thermostat that signals a
fan to turn on; operable vents and dampers that allow or restrict heat flow; low-emissivity blinds; and awnings.
PRINCIPLES OF PASSIVE SOLAR DESIGN
•Site Selection –
Select a site protected
from afternoon sun with
good solar access, and is
open to cool breezes while
remaining sheltered from
cold winds during winter.
•Orientation –Position
the building’s long axis
toward solar south with
will maximize solar gain
during winter month and
limit western exposure in
the summer.

5. •Window Placement –
Choose energy efficient
windows, arranging them
with consideration to
minimize summer heat gain
and maximize winter heat
gain.
•Shading –Configure
shading devices, such as
eave overhangs or
external shading devices
to permit low winter sun
into building and high
summer sun out.
•Room Layout –Rooms used more
frequently placed on the south side for optimal
use of natural light during day.
•Insulation –Supply a continuous
insulation layer, with thickness appropriate to
climate, surrounding the entire conditioned
space of the building, minimizing loss of heat
during winter and heat gain in summer.
•Air-sealing –Supply a
continuous air-barrier
surrounding the entire
building envelope, in contact
with the insulation layer,
minimizing loss of heat in
winter and heat gain in
summer months.
•Ventilation –Every building must have
ventilation in order to sustain good indoor air
quality. Energy efficient, airtight buildings need a
heat (or energy) recovery ventilation system.

6. •Thermal Mass –Heavy materials such as brick, concrete, tile and
stone should be utilized in appropriate thicknesses and areas to insulate
the building envelope to store heat and help balance temperature
fluctuations.
•Landscaping –Carefully planned landscaping and planting can aid in
maximizing performance of Passive Solar Design and assist with
imperfect situations and site problems.
Passive coolingis where the building design and materialsare used to control temperature in hot weather.
There are 2 basic components to passive cooling: cooling the building and cooling people.
Cooling buildings is about:
•reducing heat gain (for example, by installing insulation and shading windows, walls and roofs)
•increasing heat loss and access to cooling sources (for example, by using earth coupling and encouraging air
movement).

7. Passive cooling is the least expensive and most
sustainableway of cooling the home, especially
considering the environment. We can achieve a
comfortableindoor environment by designing
or modifying our house. As we all know, climate
changes these days have created so much
discomfort for the inhabitantsthat passive cooling
is becoming increasingly important. Climate change
increasesthe average temperatures, making it
difficult for us because of heat waves, hot air, and
other things
•It reduces the overall energy consumption
of the house.
•It is a cost-effectivemethod or technique.
•It is a sustainable way.
•It improves indoor air quality.
•It provides a better and more comfortable indoor
environment.
Why is passive cooling important?

8. PASSIVE COOLING TECHNIQUES
Reducing heat gain
Heat enters and leaves a home through the whole building envelope –the roof, walls, floor and glazing. The
internal layout —walls, doors and room arrangements also affects heat distribution within a home.
•Earth coupling
Earth coupling is achieved when the thermalmass of the slab
is in direct contact with theadditional thermal mass of the
earth below.This greatly enhances thermal
performance.Earth coupling is most simply achieved
usingslab-on-ground construction.
Earth coupling allows the floor slab of a well insulated house to
achieve the same temperature as the earth a few metres below the
ground surface, where temperatures are more stable(cooler in
summer, warmer in winter). In winter, added solar gain boosts the
surface temperature of the slab to a very comfortable level.

9. •Roof space ventilation
Well-ventilated roof spaces contribute to passive cooling by
providing a buffer zone between internal and
external spaces in the most difficult area to shade: the
roof.
Ventilators such as whirlybirdscan reduce the
temperature differential across ceiling insulation,
increasing its effectiveness. The use of foil insulation and
light-coloured roofing limits radiant heat flow into the
roof space. Always ensure that the ceiling is sealedagainst
any draughts.
•Shading of glazing
Glazing is the main source of heat gain (through
direct radiationand conduction), and of cooling
(through cross, stack and fan-drawn
ventilation; cool breeze access and night
purging). Choosing windows with good thermal
performance (for example, double glazing) will
reduce the heat gain caused by sun hitting the window.
But preventing sun from hitting the window in the first
place will have a much larger effect.

10. •Landscape design
Outdoor spaces around your home can be a source of heat
for your home. Gardens and green plants, rather than hard
surfaces, will help to reduce the temperature of air moving over
those surfaces and in and around your home. Plants and soil
provide a cooling effect through the process of
evapotranspiration, and plants can also be used to provide
shadeand funnel cooling breezes. Green roofs can
also provide additional insulationto roofs.
Increasing heat loss
Sources of passive cooling which comes from a single, predictable source —the sun. The key to most
sources of passive cooling is air movement. Air movement cools buildings by carrying heat out of the
building and replacing it with cooler external air. Moving air can also carry heat to mechanical cooling
systems where it can be removed by heat pumps and then recirculated. Air movement also cools
people by increasing evaporationof perspiration.

11. •Cool breezes
Where the climate provides cooling breezes, maximising
their flow through a home is a key component of passive
cooling. Cool breezes work best in narrowor open-plan
layouts and rely on air-pressure differentials caused by
wind or breezes. They are most effective in:
•buildings with narrow floor plans or open-plan layouts
•locations without long periods of high external
temperature.
•locations where windowscan be left open(quiet
locations with good outdoor air quality).
•Evaporation
As water evaporates, it draws in heatfrom surrounding air.
Evaporation is therefore an effective passive cooling method. It
works best with low relative humidity (70% or less), because
air with lower humidity has a greater capacity to take up the
evaporated water vapour than air with high humidity.
Rates of evaporation are increased by air movement –thus
breezes or fans can increase evaporative cooling.

12. •Convection
The rule of convection is that warm air rises and cool air
falls. Stack ventilation relies on the increased buoyancy of
warm air relative to the higher density of cooler air. The lighter
warm air rises and if allowed, will escape the building through high-
level outlets (windows or vents). Stack ventilation can increase
cross-ventilation and overcome many of the limitationsof
unreliable cooling breezes. Even when there is no breeze,
convection allows heat to leave a building via controllable openings
such as high clerestory windows, roof ventilatorsor
vented ridges.
Cooling methods
•Windows
In rooms where it is not possible
to place windows in opposite or
adjacent walls for cross-
ventilation, you can place
projecting fins on the windward
side to create positive and
negative pressure to draw
breezes through the room.

13. •Ceiling or personal fans
Air movement relative to fan position
•Whole-of-house fans •Air-conditioning
Air-conditioning in warm humid conditions
may cause condensation problems if not
anticipated and managed properly
Whole-of-house fans should be positioned
centrally (for example, in the roof, stairwell
or hallways)
•Hybrid
cooling
systems
•Solar
chimneys
Switch and circuit
diagrams for
subordinating air-
conditioning to
ceiling fans
Solar chimneys
may provide
ventilation and
cooling with
careful design