HVAC Lecture, heating, ventilation, and air conditioning

1. Passive design

2. Objectives
After completing this unit, the student should be able to
1 Discuss the procedure in passive design
2. Design a house using passive design techniques
Key Words
Direct Gain Thermal Mass Solarium Solar Orientation
Overhung Building Envelope Sunshade Solar Control

3. Introduction
In the hostile territory of the dessert many animals reverse their life
rhythm, live by night, and tuck away underground at dawn. This is how
nature smoothly operates without mechanical ventilation and heater. On
the other hand, mankind’s physical flexibility and capacity for adaptation
are relatively feeble compared to those of many animals. But man has
learned through the ages how to harness the afternoon solar radiation
for heating purpose at night.
The primary source of energy for such efficient system is solar energy.
Solar energy is a
radiant heat source that causes natural processes upon which all life
depends. The free energy source sun can be easily managed to have a
comfortable climate in a building. The basic natural processes that are
used in passive solar energy are the thermal energy flows associated
with radiation, conduction, and natural convection

4. Considering all behaviors of the relationship between the
sun and the building materials like reflection, transmission,
and absorption an economical and comfortable building will
be achieved.

5. Description
Passive solar energy systems involve designing the structures themselves
in ways that use solar energy for heating and cooling. As in
active solar design, the sun energy is not used with trapping materials
directly exposed to the sun.
Passive solar design uses nothing but the arrangements of structural
elements, windows, walls, and floors to store and distribute the sun's heat
in the winter and reject solar heat in the summer.

6. In addition to the thermal comfort of the room, passive design has
big role in the room lightings and other comfort aspects
of a room. For passive heating and cooling, the plan of the house,
careful site selection and planning, construction materials, building
features and other aspects of the home are designed to collect,
store and distribute the sun's heat in winter; and to block the sun's
rays in summer. Passive solar houses can be built in any
architectural style and in anywhere else. A "passive" solar house
provides cooling and heating to keep the home comfortable without
the use of mechanical equipment.

7. This style of construction results in homes that respond
to the environment. They typically incorporate natural
ventilation and roof overhangs to block the sun's
strongest rays during that season. Passive solar systems
make use of natural energy flows as the primary means of
harvesting solar energy. Passive solar systems can
provide space heating,/ cooling load avoidance, natural
ventilation, water heating, and day lighting.

8. Passive solar design can be applied in different ways such as
1. Building Envelope - The roof, walls, windows, floors and
internal walls of a home. The envelope controls heat gain in summer
and heat loss in winter. This process is done with the selection of
the building materials exposed to the sun directly. Well-designed
envelopes maximize cooling air movement and exclude sun in
summer. In winter, they trap
and store heat from the sun
and minimize heat loss to the
external environment. Thick
concrete walls modulate wide
swings in temperature by
absorbing heat in winter and
insulating in summer. Water
compartments provide a
thermal mass for storing heat
during the day and releasing
heat at night

9. 2. Sun space - uses a separate
solar room (solarium) to store
solar heat. A sunspace can be
built as part of a new building or as
an addition to an existing one.
Sunspaces also require a
thermal mass to store heat. “
Sun space” serves as a collector in
winter when the solar shades are open
and as a cooler
in summer when the solar shades are
closed. This method is used for both
cooling and
heating purposes.

10. 3. Direct Gain - simplest technique. Sunlight enters
a building through an opening — usually south-facing
windows. It then strikes the building's thermal mass —
usually dark colored masonry floors and/or walls in the
interior space that absorb and store the solar heat.

12. 4. Thermal Mass - any material in the home that
absorbs and stores heat. Concrete, brick, tile and
other masonry materials are the most common choices
for thermal mass in a passive solar home, these
materials absorb and release heat slowly and are easily

13. 5. Properly placed trees and vine-covered trellises
can stop summer sun on the south, east
and west sides of your home. Landscaping is one of
the best methods to keep the house
cool. The temperature inside can increase as much
as 20 degrees or more if east and west
Windows and walls are not shaded.

14. 6. 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

15. 7. Orientation - the need for auxiliary
heating and cooling is reduced, resulting in
lower energy bills and reduced greenhouse
emissions..

17. Elements of passive design:
1. aperture or collector — the large glass area through which
sunlight enters the building
2. absorber — the dark surface of the storage element that
absorbs the solar heat.
3. thermal mass — the material that stores the absorbed heat.
This can be masonry materials such as concrete, stone, and brick;
or a water tank.
4. distribution method — the natural tendency of heat to move
from warmer materials to cooler ones (through conduction,
convection, and radiation) until there is no longer a temperature
difference between the two.
5. control mechanism — to regulate the amount of sunlight
entering the aperture. This can be roof overhang to allow more
sunlight to enter in the winter, less in the summer.

18. Pop quiz
1.What is stack effect ? Demonstrate with sketch
2.What are the limitations of natural ventilation design ?
3.Give three examples of natural ventilation design application
4.List the different ways passive design can be applied in ?