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Questions and Answers
What percentage of the U.S. primary energy consumption is attributed to buildings?
What percentage of the U.S. primary energy consumption is attributed to buildings?
Which of the following factors does NOT affect conductive heat loss in buildings?
Which of the following factors does NOT affect conductive heat loss in buildings?
What is the primary energy draw for buildings in the residential and commercial sectors?
What is the primary energy draw for buildings in the residential and commercial sectors?
What is the principal metric used to estimate a building's heating and cooling needs?
What is the principal metric used to estimate a building's heating and cooling needs?
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How can the impact of energy efficiency improvements lead to increased energy use for certain technologies?
How can the impact of energy efficiency improvements lead to increased energy use for certain technologies?
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The inverse of thermal conductance is known as which of the following?
The inverse of thermal conductance is known as which of the following?
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What percentage of the nation’s electricity use is attributed to buildings?
What percentage of the nation’s electricity use is attributed to buildings?
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Which factor is NOT considered in the conductive heat loss evaluation for a building?
Which factor is NOT considered in the conductive heat loss evaluation for a building?
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What is a potential benefit of improving energy efficiency in U.S. buildings?
What is a potential benefit of improving energy efficiency in U.S. buildings?
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Which of the following is NOT a type of heat transfer involved in buildings gaining or losing heat?
Which of the following is NOT a type of heat transfer involved in buildings gaining or losing heat?
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Which property of building materials is most directly related to their effectiveness in insulating a structure?
Which property of building materials is most directly related to their effectiveness in insulating a structure?
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When considering heat transfer in buildings, which factor has the least impact if the outside temperatures are mild?
When considering heat transfer in buildings, which factor has the least impact if the outside temperatures are mild?
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What role does ventilation play in energy consumption in commercial buildings?
What role does ventilation play in energy consumption in commercial buildings?
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In the operation of an air conditioning unit, which phase of the refrigerant occurs first?
In the operation of an air conditioning unit, which phase of the refrigerant occurs first?
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If the U rating of a building component increases, what can be inferred about its heat transfer properties?
If the U rating of a building component increases, what can be inferred about its heat transfer properties?
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What is primarily required to maintain the efficiency of an HVAC system in relation to air quality?
What is primarily required to maintain the efficiency of an HVAC system in relation to air quality?
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What happens to the refrigerant as it is pumped into a warm area in an air conditioning cycle?
What happens to the refrigerant as it is pumped into a warm area in an air conditioning cycle?
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In the heating and cooling technologies mentioned, which type of heater is an example of a resistance-based heating system?
In the heating and cooling technologies mentioned, which type of heater is an example of a resistance-based heating system?
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Which of the following factors directly influences conduction in buildings?
Which of the following factors directly influences conduction in buildings?
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What is the primary energy draw of an air conditioning unit during its operation?
What is the primary energy draw of an air conditioning unit during its operation?
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Study Notes
Energy Efficiency Lesson 18
- Two-thirds of US primary energy consumption is lost as wasted energy
- Efficiency improvements could reduce energy use for the same services, potentially minimizing greenhouse gas emissions or expanding access to services
- Buildings are a significant energy sink (40% of US primary energy consumption, 70% of electricity)
- Space conditioning (heating and cooling) is the largest energy consumer within buildings
Heat Transfer in Buildings
- Buildings gain or lose heat through conduction and convection
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Conduction: Heat moves through walls, windows, floors, and roofs from a higher temperature to a lower temperature
- The higher the R-value of a material, the better its insulation properties
- Greater outside-inside temperature differences increase heat transfer rates
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Convection: Heat transfer through the movement of air or fluids (Warm air rises, cool air sinks)
- This depends on interior volume and temperature differences
- Ventilation (air circulation) is key for indoor air quality and preventing disease transmission
Heating and Cooling Technologies
- Heating: Furnaces and electric heaters
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Cooling: Air conditioners (A/C)
- A/C operation is the reverse of a heat engine
- A refrigerant absorbs heat in a warm area, turns to a gas, is compressed, releases heat to the outside, and then returns to a liquid state through an expansion process
- Main energy input is for pumping and compressing the refrigerant, which is less than the heat removed from the space
Building Energy Use Calculation
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Degree-Days: A method to estimate energy needs
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Cooling Degree Days (CDD): For calculating cooling needs.
- Calculated by subtracting 65°F from the average daily temperature
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Heating Degree Days (HDD): For calculating heating needs.
- Calculated by subtracting the average daily temperature from 65°F
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Cooling Degree Days (CDD): For calculating cooling needs.
- This method factors in the difference in indoors and outdoors temperature which is the main determining factor for cooling or heating an enclosed space
Efficiency Implications
- Potential for a tremendous energy saving from efficiency improvements across all buildings
- Achieving large energy savings typically requires substantial improvements across an entire building stock, which makes coordination and financing issues important
- Efficiency improvements in lighting are an example where greater use of the improved technologies can lead to higher energy consumption despite the improvement in efficiency.
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Description
Explore the critical concepts of energy efficiency in buildings, focusing on heat transfer mechanisms such as conduction and convection. Understand the importance of improving energy efficiency to reduce waste and emissions. This lesson emphasizes the role of buildings as major energy consumers and the opportunities for enhancement.
