1. RESIDENTIAL HVAC (HEAT LOSS & GAIN)
Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
RESIDENTIAL HVAC (HEAT LOSS & GAIN)
The Romans are well known for their public water supply and waste water systems. However, except for the wealthy, most access points to the systems were located outside of buildings.
APPLICATIONS OF TECHNOLOGY
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2. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
WHAT IS HEAT TRANSFER?
Heat transfer is the exchange of thermal energy from one physical body to another by dispelling heat.
Heat is always transferred from a region of high temperature to a region of low temperature
Thermal comfort is achieved when equilibrium exists between the human body and its environment.
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Copyright 2010

3. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HOW IS HEAT TRANSFERED?
Heat may be transferred in the following ways:
Conduction: transfer of heat through direct physical contact.
What are some examples of conduction?
The Romans are well known for their public water supply and waste water systems. However, except for the wealthy, most access points to the systems were located outside of buildings.
Project Lead The Way, Inc.
Copyright 2010

4. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HOW IS HEAT TRANSFERED?
Heat may be transferred in the following ways:
Convection: transfer of heat through the circulation of a liquid or gas.
What are some examples of convection?
The Romans are well known for their public water supply and waste water systems. However, except for the wealthy, most access points to the systems were located outside of buildings.
Project Lead The Way, Inc.
Copyright 2010

5. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HOW IS HEAT TRANSFERED?
Heat may be transferred in the following ways:
Radiation: transfer of heat through rays, waves, or particles.
The Romans are well known for their public water supply and waste water systems. However, except for the wealthy, most access points to the systems were located outside of buildings.
What are some examples of radiation?
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Copyright 2010

6. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HEAT LOSS/GAIN
When do we typically experience heat loss? What is the temperature difference indoors vs outdoors?
Heat loss normally occurs during the winter when the indoor tempature is higher than the outdoor temperature.
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Copyright 2010

7. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HEAT LOSS/GAIN
When do we typically experience heat gain? What is the temperature difference indoors vs outdoors?
Heat gain normally occurs during the summer when the indoor tempature is lower than the outdoor temperature.
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Copyright 2010

8. WHAT ARE SOME CAUSES OF HEAT LOSS/GAIN?
Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
WHAT ARE SOME CAUSES OF HEAT LOSS/GAIN?
openings (windows, doors, other places where air may leak into the building)
lighting
equipment
people
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Copyright 2010

9. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
THERMAL UNITS
Btu (British Thermal Unit) – the amount of heat need to raise the temperature of 1 pound water by 1 degree
1 watt = 3.4 btu/hr
1 ton = 12,000 btu/hr (used in air conditioning)
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Copyright 2010

10. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
R-VALUE VS U-FACTOR
R-value (thermal resistance): the ability of a material to resist heat traveling through it. How effective is this material in terms of insulation?
U-factor (heat conductivity): measurement of the rate of transfer of heat. How well does heat travel through this material?
WHAT’S RELATIONSHIP BETWEEN R-VALUE AND U-FACTOR?
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Copyright 2010

11. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
FORMULA FOR HEAT LOAD
Q' = AU T
Where Q' = Total cooling/heating load in
A = Area under investigation in ft2
U = Coefficient of heat conductivity in
T = Difference in temperature between outside and inside conditions in °F
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Copyright 2010

12. HEAT LOSS THROUGH A WALL: AREA
Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HEAT LOSS THROUGH A WALL: AREA
Height = 8 ft
Length = 21 ft
Area = 8 ft x 22 ft = 176 ft²
Subtract area of any openings
2 Windows (3ft wide x 4ft tall)
2(12ft2)=24 ft²
Wall Area
176 ft² -24 ft² =152 ft²
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Copyright 2010

13. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HEAT LOSS THROUGH A WALL: R-VALUE
Each material in the construction of wall has its own R-Value. Some R-Values are based on the thickness of the material.
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Copyright 2010

14. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HEAT LOSS THROUGH A WALL: R-VALUE
Outside Air Film neglect
Siding
Vapor Barrier 0.06
Plywood 0.62
Insulation
Drywall 0.45
Inside Air Film 0.68
Total R-Value
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15. Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
HEAT LOSS THROUGH A WALL: U-VALUE
Total R-Value= 15.86
U = .063
(Do not round up)
15.86
Cut-off at three decimal places
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Copyright 2010

16. USING ENGINEERING DESIGN DATA
Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
USING ENGINEERING DESIGN DATA
T = TEMPERATURE DIFFERENTIAL
Baltimore is listed twice in the Design Data because temperature data is taken from the city and the airport.
Source: 2012 International Plumbing Code, Table D101
For heating calculations, we use a temperature that has been exceeded 97.5% of the year.
For cooling calculations we use a temperature value has been exceeded only 2.5% of the year.
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17. T = TEMPERATURE DIFFERENTIAL
Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
T = TEMPERATURE DIFFERENTIAL
The difference between the design outside temperature and the design inside temperature
Design Outside Temperature
13 °F
Design Inside Temperature
68 °F
(in Baltimore, MD)
Inside Design Temperatures typically range from 67 °F to 82 °F
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18. TOTAL HEAT LOSS (OR TRANSMISSION LOAD) Q' = AU T
Heating Ventilation and Air Conditioning
Civil Engineering and Architecture
Unit 2 – Lesson 2.3 – Services and Utilities
TOTAL HEAT LOSS (OR TRANSMISSION LOAD) Q' = AU T
Q' = AU T
A = (8 ft) (21 ft) = 186 ft2 – 24 ft2 (WINDOWS)= 152 ft2
U = .063
T = 68°F °F = 55 °F
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Copyright 2010