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 Project Lead The Way, Inc. Copyright 2010

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. Project Lead The Way, Inc. Copyright 2010

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

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

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? Project Lead The Way, Inc. Copyright 2010

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. Project Lead The Way, Inc. Copyright 2010

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. Project Lead The Way, Inc. Copyright 2010

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 Project Lead The Way, Inc. Copyright 2010

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) Project Lead The Way, Inc. Copyright 2010

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? Project Lead The Way, Inc. Copyright 2010

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 Project Lead The Way, Inc. Copyright 2010

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 Project Lead The Way, Inc. Copyright 2010

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. Project Lead The Way, Inc. Copyright 2010

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 1.05 Vapor Barrier 0.06 Plywood 0.62 Insulation 13.00 Drywall 0.45 Inside Air Film 0.68 Total R-Value 15.86 Project Lead The Way, Inc. Copyright 2010

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)     0.06305 15.86 Cut-off at three decimal places Project Lead The Way, Inc. Copyright 2010

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. Project Lead The Way, Inc. Copyright 2010

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 Project Lead The Way, Inc. Copyright 2010

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 - 13°F = 55 °F   Project Lead The Way, Inc. Copyright 2010