1. Environmental Control
Systems-I
Lecture-03

2. TOPICS IN ORDER:
- Criteria for thermal control
- Climatic Zones
- Climatic Data used in design of Buildings
- Orientation of buildings and rooms within buildings

3. CRITERIA FOR THERMAL CONTROL:
Thermal comfort can be achieved by both active and passive techniques. In passive
system, by using natural ventilation, solar shading and intelligent building design. In
active design, by using HVAC systems and modern related technology.

4. THERMAL COMFORT:
Thermal comfort is a subjective assessment by a person expressing their satisfaction
with their local thermal environment. In practice, there are a number of variables
that influence the body’s heat balance with the environment, and in turn that
person’s perception of thermal comfort.
Personal Factors:
• Occupant activity
• Clothing
Environmental Factors:
• Air temperature
• Radiant temperature
• Air velocity
• Humidity

5. SWEAT
EXHALATION
INSENSIBLE
PERSPIRATION
EVAPORATION
CONVECTION
CONDUCTION
RADIATION
RADIATION
COMPONENTS CONTRIBUTING TO THERMAL COMFORT

6. “PERSONAL FACTORS”
1. OCCUPANT ACTIVITY:
People have different metabolic rates that can fluctuate due to activity level and environmental
conditions. The ASHRAE Standard defines metabolic rate as the level of transformation of chemical
energy into heat and mechanical work by metabolic activities within an organism, usually expressed in
terms of unit area of the total body surface. Metabolic rate is expressed in met units, which are defined
as follows:
1 met = 58.2 W/m²
which is equal to the energy produced per unit surface area of an average person seated at rest. The
surface area of an average person is 1.8 m² (19 ft²).
FACTORS AFFECTING METABOLLIC RATE:
• Food and drink habits may have an influence on metabolic rates, which indirectly influences thermal
preferences. These effects may change depending on food and drink intake.
• Body shape is another factor that affects thermal comfort. Heat dissipation depends on body surface
area. A tall and skinny person has a larger surface-to-volume ratio, can dissipate heat more easily, and
can tolerate higher temperatures more than a person with a rounded body shape.

7. METABOLLIC RATES OF A PERSON PERFORMING DIFFERENT ACTIVITIES

8. 2. CLOTHING:
The amount of thermal insulation worn by a person has a substantial impact on thermal comfort, as it
influences the heat loss and consequently the thermal balance. Layers of insulating clothing prevent
heat loss and can either help keep a person warm or lead to overheating. Generally, the thicker the
garment is, the greater insulating ability it has. Depending on the type of material the clothing is made
out of, air movement and relative humidity can decrease the insulating ability of the material.

9. CLOTHING RATES OF A PERSON PERFORMING DIFFERENT ACTIVITIES

10. “ENVIRONMENTAL FACTORS”
1. AIR TEMPERATURE:
The air temperature is the average temperature of the air surrounding the occupant, with respect to
location and time. Air temperature is measured with a dry-bulb thermometer.
2. RADIANT TEMPERATURE:
The radiant temperature is related to the amount of radiant heat transferred from a surface, and it
depends on the material’s ability to absorb or emit heat, or its emissivity. The mean radiant
temperature depends on the temperatures and emissivity of the surrounding surfaces as well as
the view factor, or the amount of the surface that is “seen” by the object. So the mean radiant
temperature experienced by a person in a room with the sunlight streaming in varies based on how
much of his/her body is in the sun.

11. “ENVIRONMENTAL FACTORS”
3. AIR VELOCITY:
Air speed is defined as the rate of air movement at a point, without taking into consideration the
direction. According to ASHRAE Standard, it is the average speed of the air to which the body is exposed,
with respect to location and time. However, some spaces might provide strongly non uniform air velocity
fields and consequent skin heat losses that cannot be considered uniform. Therefore, the architect shall
decide the proper averaging, especially including air speeds incident on unclothed body parts, that have
greater cooling effect and potential for local discomfort.
4. RELATIVE HUMIDITY:
Relative humidity (RH) is the ratio of the amount of water vapor in the air to the amount of water vapor
that the air could hold at the specific temperature and pressure. While the human body has sensors
within the skin that are fairly efficient at feeling heat and cold, relative humidity is detected
indirectly. Sweating is an effective heat loss mechanism that relies on evaporation from the skin.

12. CLIMATIC ZONES:
Like Europe and various other countries, Pakistan is a country with wide variations in climate.
There are regions which are extremely hot as Sibbi in Baluchistan and Jacobabad in Sindh and
there are regions which are extremely cold as Gilgit, Swat, Skardu in Khyber Pukhtun Khwa.
Thus, on the basis of climatic classification data the country can be divided into seven climatic
zones:
‐ Hot and Dry
‐ Hot and Humid
‐ Warm and Humid
‐ Moderate
‐ Cold and Cloudy
‐ Cold and Dry
‐ Composite

13. DIFFERENT GEOGRAPHICAL ZONES

14. HOT AND DRY:
Deserts with hot and dry climates are warm all year round, and are extremely hot in the summer.
Usually, they have very little rainfall, making the climate extremely dry, and hard for plants and
animals to survive. There are very few plants in hot and dry deserts. Often, the only things that can
survive are short shrubs and trees. Plants that live in the desert have special abilities that allow them
to live in such a hot and dry place.
HOT AND HUMID:
In hot and humid climatic regions, high temperatures are accompanied by very high humidity levels
leading to immense discomfort. Usually areas which are coastal are close to seas are hot and humid
because of the moisture level in air is too high. Cross ventilation is hence very essential here.
WARM AND HUMID:
The climate of warm-humid zones is characterized by high rainfall and high humidity. The
temperature range is relatively high at around 30 - 35°C and is fairly even during the day and
throughout the year. Due to minimal temperature differences, winds are light or even non-existent for
longer periods. However, heavy precipitation and storms occur frequently.

15. IMPORTANT FACTORS FOR WARM-HUMID CLIMATES:
 Provide maximum ventilation and free air movement by large openings.
 Provide maximum shading of direct and diffuse solar radiation.
 Avoid heat storage.
 Use reflective outer surfaces.
 Use ventilated double roofs.
 Use vegetation to moderate the solar impact.
MODERATE:
In geography, temperate or tepid latitudes of Earth lie between the tropics and the polar regions. The
temperatures in these regions are generally relatively moderate, rather than extremely hot or cold,
and the changes between summer and winter are also usually moderate.

16. COLD AND CLOUDY:
Winters are prolonged and summers are short in this climate. There is also a fair amount of
precipitation- snow or rain, often spread across the year.
The traditional homes and villages of the sub - Himalayan region are built on hill slopes that would
receive a fair amount of sunshine. The lower floor is occupied by cattle and used for storage. The
upper floor which is away from cold and damp ground has the living rooms. The cooking area is a part
of it, in order to benefit from the heat generated by it. Low timber ceiling provide insulation and
conserve the warmth. Windows face the sun.
COLD AND DRY:
Polar climates are cold and dry, with long, dark winters. In the tundra (a treeless region bordering the
Arctic), temperatures rise above freezing for only a few months each year.
COMPOSITE OR MONSOON CLIMATE:
Tropical monsoon climates have monthly mean temperatures above 18 °C in every month of the year
and feature wet and dry seasons.

17. Hyderabad City (Wind Catchers)

18. TRADITIONAL HOUSES IN COLD AND CLOUDY REGION
TUNDRA (COLD AND DRY CLIMATE)

19. CLIMATE CLASSIFICATION CHART:
Following two charts are being used for the understanding of climatic data and requirement.
• Eco-Chart
• Comfort Zone Chart
ECO-CHART:
This chart has been adopted to give a graphic account and understanding of the following factors:
1. Solar Geometry and Shadow Pattern:
These facilitate the visualization of physical form and its response to the movement of the sun and
the shadow cast.
2. HOURS OF SUN SHINE:
This gives a physical account of the total sunshine hours available which can be made use of for heat
gain or the time period for which elimination of solar exposure must be made.

20. 3. Solar Radiation:
This gives the variation of both total and diffuse radiation giving a good idea of use and conversion of
solar energy.
4. Air Temperature:
This gives the variation of maximum mean and minimum temperature over the entire year, giving a
broad indication of the overhead, comfortable and under heated periods.
5. Degree Days:
The variation of both heating and cooling degree days over the entire year is given. This indicates the
heating and cooling loads in climatic zones.
6. Precipitation:
This gives the average precipitation on a monthly basis over the entire year, expressing the amount of
precipitation available and management required.
7. Relative Humidity:
This tells the variation of the relative humidity on a monthly basis over the entire year. Combined with
air temperature, the humidity levels serve as an indicator of strategies required for passive control of
comfort conditions in the buildings.
8. Wind Speed, Frequency and Direction:
The graphic presentation of the wind data helps in the planning and designing of the settlement as a
whole and buildings in particular.

21. COMFORT ZONE CHART:
This chart has been deployed to give the extended values of solar radiation, wind speeds and
humidity levels and their effect on the comfort zone.
Various climatic elements such as wind speed, vapor pressure, relative humidity and radiation affect
the comfort conditions in the comfort zone chart.
1. WIND SPEED:
Air movement affects body cooling. It does not decrease the air temperature but causes a sensation
of cooling due to heat loss by convection and due to increased evaporation from the body. As velocity
of air increases, the upper comfort level is raised.
2. VAPOR PRESSURE:
Vapor pressure is exerted by a variable quantity of water vapor present in atmospheric air. When the
vapor pressure increases beyond the 15 mm mark, there is a feeling of lassitude.

22. 3. HUMIDITY:
Higher value of relative humidity increases the feeling of discomfort.
4. RADIATION:
Radiation curves shown in this chart refer to the outside conditions only. An increase in radiation level
can offset the drop in the dry bulb temperature and thereby effect the comfort zone.

23. CLIMATIC DATA USED IN BUILDINGS:
Following are the main points of climatic data to be used in designing a building:
‐ Typical Landscape and Vegetation
‐ Solar Radiation
‐ Mean Temperature
‐ Relative Humidity
‐ Precipitation
‐ Winds
‐ Sky Conditions
‐ Miscellaneous

24. BUILDING ORIENTATION:
Building orientation refers to the way a building is situated on a site and the positioning of windows,
rooflines, and other features. A building oriented for solar design takes advantage of passive and
active solar strategies.
Passive solar strategies use energy from the sun to heat and illuminate buildings. Building orientation
and building materials also facilitate temperature moderation and natural daylighting.
Active solar systems use solar collectors and additional electricity to power pumps or fans to
distribute the sun's energy. Heat is absorbed and transferred to another location for immediate
heating or for storage for use later.

25. Living Room
Dining Room
Children Room
Storage
Garage
Central heating

26. HOW TO OPTIMIZE BUILDING ORIENTATION:
The most convenient way is to incorporate passive solar systems into a building during the initial
design. Passive solar systems utilize basic concepts incorporated into the architectural design of the
building. They usually consist of:
‐ Rectangular floor plans elongated on an east-west axis
‐ Glazed south-facing wall
‐ Thermal storage medium exposed to the solar radiation
‐ Light shelves/overhangs or other shading devices which sufficiently shade the south-facing
elevation from the summer sun; south elevation overhangs should be horizontal while east and
west elevations usually require both horizontal and vertical overhangs
‐ Windows on the east and west walls, and preferably none on the south walls

28. “Lecture No. 04”
TOPICS IN ORDER:
- Thermal transmittance of walls, floors and roofs
- Insulation and techniques
- Reflectivity of Building’s Surfaces