This document provides a summary of a lecture on heat transfer in buildings and climatic design. It covers several topics: 1. Methods of heat transfer including conduction, convection, and radiation. 2. Factors that affect thermal comfort including air temperature, relative humidity, air velocity, and clothing insulation. 3. The concept of microclimate and how indoor microclimate impacts user comfort and health. 4. Guidelines for designing buildings for thermal comfort including typical environmental variables like dry bulb temperature, relative humidity, and air velocity.

1. Prepared by
Dr. Nedhal Al-Tamimi
Arch. Eng. Dept.,
Faculty of Engineering
Najran University, KSA
naaltamimi@nu.edu.sa
Heat
Transfer
in
Buildings
Lecture
No. 3
Climatic Design AE 353-2

2. Scope
of
Presentation
1. Review
2. Heat Transfer Methods
▪ Conduction
▪ Convection
▪ Radiation
3. What is a Microclimate?
4. Variables Affecting Comfort
5. Designing for Comfort

3. Section 1 Review
Generalized Climate Regions

4. The Major Climates
▪ A - Tropical Rainy Climates
▪ B - Dry, Arid, and Semiarid
Climates
▪ C - Mesothermal Climates
(rainy, mild winter)
▪ D - Microthermal Climates
(rainy, cold winter)
▪ E - Polar Climates
▪
‫المناخ‬
‫الممطر‬ ‫االستوائي‬
▪
‫المناخ‬
‫القاحلة‬ ‫واألراضي‬ ‫الجاف‬
‫القاحلة‬ ‫وشبه‬
▪
‫الحرارة‬ ‫معتدل‬ ‫المناخ‬
(
‫معتدل‬ ‫شتاء‬ ،‫ممطر‬
)
▪
‫البارد‬ ‫المناخ‬
(
‫بارد‬ ‫وشتاء‬ ‫ممطر‬
)
▪
‫القطبي‬ ‫المناخ‬
The Koeppen System
Section 1 Review

5. Section 2 Heat Transfer
Heat and Temperature
Heat is a form of energy, contained in substances as molecular
motion or appearing as electromagnetic radiation in space.
‫د‬ّ‫ع‬‫ت‬
‫الحرارة‬
ً
‫نوعا‬
‫من‬
‫أنواع‬
،‫الطاقة‬
‫تنشأ‬
‫من‬
‫ك‬ّ‫تحر‬
‫الذرات‬
‫أو‬
‫الجزيئات‬
‫الداخلة‬
‫في‬
‫تركيب‬
‫مادة‬
،‫ما‬
‫ويتزامن‬
‫مع‬
‫هذه‬
‫الحركة‬
‫ت‬
‫وليد‬
‫الطاقة‬
‫ويكون‬
‫ذلك‬
‫بإحدى‬
‫الطرق‬
‫الرئيسية‬
‫لتوليد‬
،‫الطاقة‬
‫وهي‬
:
‫التفاعالت‬
،‫الكيميائية‬
‫التفاعالت‬
،‫النووية‬
‫االشعاع‬
‫الكهرمغناطيس‬
،‫ي‬
‫الحركة‬
.
Temperature (T) is the symptom of the presence of heat in a
substance. Measured by one of the following units: Celsius
scale, Kelvin scale and Fahrenheit.
‫عرف‬ُ‫ت‬
‫درجة‬
‫الحرارة‬
‫بأنها‬
‫ر‬ّ‫ش‬‫المؤ‬
‫على‬
‫الكمية‬
‫التي‬
‫يحتويها‬
‫أي‬
‫جسم‬
‫من‬
‫الطاقة‬
‫الحرارية‬
،‫ويختزنها‬
‫كما‬
‫يمكن‬
‫تعريفها‬
‫أيض‬
ً
‫ا‬
‫بأنها‬
‫ذلك‬
‫المؤشر‬
‫الذي‬
‫يكشف‬
‫عن‬
‫مدى‬
‫الحركة‬
‫التي‬
‫يمتلكها‬
‫جسم‬
‫بين‬
،‫ذراته‬
‫وتستخدم‬
‫وحدات‬
‫قياس‬
‫الحرارة‬
‫التالية‬
‫الذكر‬
‫لتحديد‬
‫مدى‬
‫برودة‬
‫الجسم‬
‫أو‬
،‫سخونته‬
‫وتلعب‬
ً
‫دورا‬
ً
‫مهما‬
‫في‬
‫تحديد‬
‫االتجاه‬
‫الذي‬
‫تنتقل‬
‫فيه‬
‫الحرارة‬
‫بشكل‬
‫تلقائي‬
.
Heat and temperature are subjected to the laws of
thermodynamics.

6. Section 2 Heat Transfer
▪ Thermodynamics is the science of the flow of heat and of its
relationship to mechanical works.
▪ The first law of thermodynamics is the principle of
conservation of energy. Energy cannot be created or destroyed
▪ The second law of thermodynamics states that heat (or
energy) transfer can take place spontaneously in one direction
only: from a hotter to a cooler body, or generally from a higher
to a lower grade state (same as water flow will take place only
downhill).
▪ In physics and chemistry, heat refers to a process of transfer of
energy between a system and its surroundings other than by
work or transfer of matter.
Thermodynamics

7. Heat flow from a high to a low temperature zone can take place in
three forms: conduction, convection and radiation.
▪ In solids, this heat is transferred through conduction
▪ In liquids and gases heat is transferred through convection
▪ Objects that are hot emit heat through infrared radiation
▪ Humans transfer latent heat by evaporation from the skin
Section 2 Heat Transfer

8. Section 2 Heat Transfer

9. ▪ Conduction is the transfer of heat through
materials by the direct contact of matter.
▪ Dense metals like copper and aluminum are
very good thermal conductors.
Section 2 Heat Transfer
1. Conduction

10. Section 2 Heat Transfer
1. Conduction

11. Section 2 Heat Transfer
1. Conduction
Conductivity is a material property, regardless of its
shape or size. The corresponding property of a
physical body (e.g. a wall) is the conductance (C)
measured between the two surfaces of the wall. For a
single layer it is the conductivity, divided by
thickness.
Transmittance, or U-value includes the
surface effects and it is the most
frequently used measure. This is the
heat flow density (W/m2) with 1K
temperature difference (T) between air
inside and air outside in units of
W/m2K.

12. ▪ Convection is the transfer of
heat by the motion of liquids
or gases.
▪ Convection occurs because
currents flow when hot gas
rises and cool gas sink.
▪ Convection in liquids also
occurs because of differences
in density.
Section 2 Heat Transfer
2. Convection

13. Section 2 Heat Transfer
2. Convection

14. ▪ Radiation is heat transfer by
electromagnetic waves.
▪ Thermal radiation is
electromagnetic waves
(including light) produced by
objects because of their
temperature.
Section 2 Heat Transfer
3. Radiation

15. Section 2 Heat Transfer
3. Radiation

16. Building Envelope
(Architects)
User Requirements
(Microclimate)
Climate Condition
(Outdoor)
Section 2 Heat Transfer
Application: Energy-efficient Buildings

17. Section 2 Heat Transfer
Application: Energy-efficient Buildings

18. These are climates that exist over small areas,
where the conditions of temperature, air, relative
humidity, light and noise are different to the
general surroundings.
‫مفهومًالميكرومناخًللفضاءاتًالمبنية‬
:
‫يعطيًللمستخدمينًا‬
ً‫لراحة‬
‫ًويحملًكلًالمواصفاتًالصحيةًوالحالةًالن‬،‫والقدرةًعلىًالعمل‬
‫فسية‬
.
‫وعناصرها‬
:
ً‫الحرارةًوالهواءًوالرطوبةًالنسبيةًوًالضوء‬
‫والضوضاء‬
.
Section 3 What is a Microclimate?

19. We spend around 93% of our time inside buildings, good indoor
microclimate is the most effective way to improve the human
physiological and thermal comfort.
Why studying microclimate is an important?
Section 3 What is a Microclimate?

20. User Requirements
(Indoor)
Air Temperature
Relative humidity
Lighting quality
Noise Pollution
Air velocity
Air quality
Section 4 Variables Affecting Comfort
Thermal Variables Non-Thermal Variables

21. ً‫تمثلًالشمسًوالرياحًأهمًالمؤثراتًالخارجيةًلتحقيق‬
‫مناخًد‬
ً‫اخلي‬
ً‫مالئم‬
‫داخلًالفراغاتًالمبنية‬
‫فهماًالمؤثرانًفي‬
:
▪
‫درجةًالحرارة‬
▪
‫الرطوبة‬
‫النسبية‬
▪
‫التحركًالهوا‬
‫ئ‬
‫ي‬
▪
‫جودةًالهواء‬
▪
‫شدةًاالضاءة‬
▪
‫انتقالًالصوت‬
‫متغيرات‬
‫حرارية‬
‫متغيرات‬
‫غير‬
‫حرارية‬
Section 4 Variables Affecting Comfort

22. Air Temperature Relative humidity Air velocity
Section 4 Variables Affecting Thermal Comfort

23. Section 5 DESIGNING FOR COMFORT
Fundamentals of Thermal Comfort
Thermal Comfort:
Is the condition of mind which expresses satisfaction with the
thermal environment and is assessed by subjective evaluation.

24. Section 5 DESIGNING FOR COMFORT
Fundamentals of Thermal Comfort
What is Thermal Comfort?
.absence of irritation or discomfort due to heat or cold..
(Givoni, 1969)
Thermal comfort: is that condition of mind which expresses
satisfaction with the thermal environment. Because there are large
variations, both physiologically and psychologically, from person
to person, it is difficult to satisfy everyone in a space.
(ASHRAE Standard 55, 2010)

25. Section 5 DESIGNING FOR COMFORT
Fundamentals of Thermal Comfort
▪ To carry out statistical analysis numerical values were
assigned to subjective comfort votes.
▪ First such scale was developed in 1927 by Yaglou.
▪ In terms of sensations, thermal comfort is described as a
thermal sensation of being neither too warm nor too cold.
▪ ASHRAE proposed a similar seven point scale to thermal
sensations which are shown below:

26. Section 5 DESIGNING FOR COMFORT
Six Factors for Thermal Comfort
The six factors affecting thermal comfort are both environmental and personal.
These factors may be independent of each other, but together contribute to the
thermal comfort of building users

27. Section 5 DESIGNING FOR COMFORT
Six Factors for Thermal Comfort
Environmental factors:
▪ Air temperature
This is the temperature of the air surrounding the body. It is usually given in degrees Celsius (°C).
▪ Radiant temperature
Thermal radiation is the heat that radiates from a warm object. Radiant heat may be present if there are
heat sources in an environment. Examples include: the sun; fire; electric fires; ovens; kiln walls; cookers
▪ Air velocity
This describes the speed of air moving across the employee and may help cool them if the air is cooler
than the environment.
▪ Humidity
Relative humidity is the ratio between the actual amount of water vapour in the air and the maximum
amount of water vapour that the air can hold at that air temperature.
Personal factors:
▪ Clothing Insulation
Thermal comfort is very much dependent on the insulating effect of clothing on the wearer.
▪ Metabolic rate/heat
The more physical work we do, the more heat we produce. The more heat we produce, the more heat
needs to be lost so we don’t overheat

28. 1. Dry Bulb Temperature
2003 ASHRAE 74oF (23oC) - 78oF (26oC)
KSA Summer (26-28oC) Winter (20-22oC)
2. Relative Humidity
40 - 60%
KSA Summer (30-50%) Winter (40-60%)
3. Air Velocity
0.1 m/s
KSA Summer (0.1-0.25m/s) Winter (0.07-0.1m/s)
Section 5 DESIGNING FOR COMFORT
Typical Environmental Variables

29. 5. Clothing insulation
4. Metabolic rate
Section 5 DESIGNING FOR COMFORT
Typical Personal Variables

30. Sun and Architecture
Next Lecture
4
1. How to protect the Buildings from
the Sun.
2. Solar Geometry.
3. Solar Control & Shading Devices.

31. Climatic Design Thank You
Dr. Nedhal Al-Tamimi
AE 353-2