Podcast
Questions and Answers
What is the discharge coefficient value for sharp-edge orifices?
What is the discharge coefficient value for sharp-edge orifices?
Which flow condition is characterized by narrow cracks in buildings?
Which flow condition is characterized by narrow cracks in buildings?
What defines the effective leakage area (ELA) in buildings?
What defines the effective leakage area (ELA) in buildings?
How does the pressure difference affect the discharge coefficient of openings?
How does the pressure difference affect the discharge coefficient of openings?
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What is a characteristic of large cracks in buildings?
What is a characteristic of large cracks in buildings?
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What does the term 'measurements of airflow due to infiltrations' mainly relate to?
What does the term 'measurements of airflow due to infiltrations' mainly relate to?
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What type of flow equation is defined for narrow cracks?
What type of flow equation is defined for narrow cracks?
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Which factor is NOT related to the calculation of air infiltrations?
Which factor is NOT related to the calculation of air infiltrations?
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What primarily causes air to flow in mechanical ventilation systems?
What primarily causes air to flow in mechanical ventilation systems?
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What characterizes exhaust ventilation systems?
What characterizes exhaust ventilation systems?
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In the context of air infiltrations, which is a key distinction to understand?
In the context of air infiltrations, which is a key distinction to understand?
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Which of the following best describes the fundamentals of air movement?
Which of the following best describes the fundamentals of air movement?
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What is the primary purpose of measuring airflows due to infiltrations?
What is the primary purpose of measuring airflows due to infiltrations?
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What term is used to describe the distribution of unintended air leakages in a building?
What term is used to describe the distribution of unintended air leakages in a building?
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How can air infiltrations significantly impact a building?
How can air infiltrations significantly impact a building?
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What is the primary focus of air infiltration in buildings?
What is the primary focus of air infiltration in buildings?
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What aspect of air leakages is crucial to address in energy performance of buildings?
What aspect of air leakages is crucial to address in energy performance of buildings?
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What factor contributes to air leakages in buildings?
What factor contributes to air leakages in buildings?
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Which method is commonly used to measure airflow due to infiltrations?
Which method is commonly used to measure airflow due to infiltrations?
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Which of the following describes the nature of air movement in buildings?
Which of the following describes the nature of air movement in buildings?
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Which characteristic is NOT typically associated with cracks in buildings?
Which characteristic is NOT typically associated with cracks in buildings?
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How do buildings typically maintain comfortable interior conditions?
How do buildings typically maintain comfortable interior conditions?
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What is the importance of calculating air infiltrations in buildings?
What is the importance of calculating air infiltrations in buildings?
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What is a fundamental concept in understanding air transfer in buildings?
What is a fundamental concept in understanding air transfer in buildings?
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What must be considered in addition to wind pressure when assessing air infiltration in buildings?
What must be considered in addition to wind pressure when assessing air infiltration in buildings?
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Which parameter directly affects the pressure gradients caused by air temperature differences?
Which parameter directly affects the pressure gradients caused by air temperature differences?
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In which type of area would you generally expect to find a higher air infiltration value?
In which type of area would you generally expect to find a higher air infiltration value?
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What does the primed value in air measurement refer to?
What does the primed value in air measurement refer to?
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What type of air leakages would be most likely found in a rural area with trees?
What type of air leakages would be most likely found in a rural area with trees?
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What specific factors are vital in the measurements of airflow due to infiltrations?
What specific factors are vital in the measurements of airflow due to infiltrations?
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What contributes to the buoyancy-driven stack pressure in a building?
What contributes to the buoyancy-driven stack pressure in a building?
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In the context of air infiltrations, what does a rural area with low buildings generally indicate?
In the context of air infiltrations, what does a rural area with low buildings generally indicate?
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What does the Reynolds number help classify in the context of air infiltration?
What does the Reynolds number help classify in the context of air infiltration?
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In the equation for calculating airflow, which factor is crucial for determining the pressure difference?
In the equation for calculating airflow, which factor is crucial for determining the pressure difference?
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What is one of the primary purposes of measuring airflow due to infiltrations?
What is one of the primary purposes of measuring airflow due to infiltrations?
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Which term in the airflow calculation equation is NOT related to flow geometry?
Which term in the airflow calculation equation is NOT related to flow geometry?
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What does the term 'M' in the airflow equation depend on?
What does the term 'M' in the airflow equation depend on?
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Which aspect is crucial for understanding the analogies made between cracks and ducts?
Which aspect is crucial for understanding the analogies made between cracks and ducts?
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Why is assessing the distribution of air leakages important?
Why is assessing the distribution of air leakages important?
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The basic concepts of air movement in buildings can influence which of the following?
The basic concepts of air movement in buildings can influence which of the following?
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What pressure situation do mechanical extract ventilation systems create indoors?
What pressure situation do mechanical extract ventilation systems create indoors?
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What determines the air infiltration or exfiltration created by ventilation systems?
What determines the air infiltration or exfiltration created by ventilation systems?
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Which of the following factors contributes to total air infiltration in a building?
Which of the following factors contributes to total air infiltration in a building?
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When considering pressure components in an air infiltration analysis, what must be taken into account?
When considering pressure components in an air infiltration analysis, what must be taken into account?
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What is the characteristic of mechanical supply systems in relation to pressure situations?
What is the characteristic of mechanical supply systems in relation to pressure situations?
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What does the equation $p = -\rho * g * z * (1 - \frac{p}{p})$ primarily represent?
What does the equation $p = -\rho * g * z * (1 - \frac{p}{p})$ primarily represent?
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What is essential to assess when measuring airflow due to infiltrations?
What is essential to assess when measuring airflow due to infiltrations?
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In terms of air movement, which of the following concepts is important for high energy performance building envelopes?
In terms of air movement, which of the following concepts is important for high energy performance building envelopes?
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Study Notes
Erasmus Mundus Joint Master Degree Program (SMACCS)
- SMACCS is an Erasmus Mundus International Joint Master Degree program
- Participating universities:
- Universidad del País Vasco (University of the Basque Country)
- International Hellenic University
- Vaasan yliopisto (University of Vaasa)
- UMONS (University of Mons)
Air Transfer in Buildings (SMACCS)
- Course Module: C1 - Heat and mass transfer in buildings. High energy performance building envelopes
- Department: Energy Engineering, University of the Basque Country
- Degree: MSc in Smart Cities and Communities
- Topic: Air transfer in buildings
-
Specific topics (table of contents):
- Introduction to air infiltration in buildings
- Basic concepts and terminology
- Characteristics and classification of cracks in buildings
- Fundamentals of air movement
- Distribution of air leakages
- Measurements of airflow due to infiltrations
- Calculation of air infiltrations
Introduction to Air Infiltration in Buildings
- Why? Addressing building airtightness is critical for energy efficiency, comfort, and indoor air quality (IAQ).
- How? Infiltration methods are central to regulating indoor climate and IAQ.
- Where? Air infiltration issues arise from numerous building components.
- What? Air infiltration is a primary consideration for building design.
- Current building designs do not always consider the issues of indoor quality in the same way as past models.
- Most adopted measures aim at decreasing heat losses via a building envelope
- Improvements in building insulation have reduced transmission losses and total losses.
- However, the relative importance of each type of loss has changed.
Basic Concepts and Terminology
- Air exchange: Replacing indoor stale air with outdoor clean air. Often requires energy input for thermal conditioning.
- Air transfer: Movement of air within a building structure, intentionally or unintentionally, through cracks or openings.
- Ventilation: The deliberate introduction of clean outdoor air to displace contaminated indoor air. Can be natural or mechanical.
- Infiltration: Air entering a building through cracks and openings that were not intentionally created. Generally uncontrolled.
- Exfiltration: Indoor air escaping the building via unintended cracks or openings.
- Natural ventilation: Airflow driven by natural forces like temperature differences or wind.
- Mechanical ventilation: Airflow driven by mechanical systems like fans.
- Balanced ventilation: Systems that introduce and extract equal quantities of air, maintaining a constant pressure and improving indoor air quality.
HVAC Systems
- Exhaust Ventilation: Removes polluted air from buildings via fans and ducts.
- Supply Ventilation: Introduces clean air into buildings via fans and ducts.
- Mechanical Ventilation Systems: Use fans and/or hoods to create appropriate pressure differences to move air, such as through a duct system.
Characteristics and Classification of Cracks in Buildings
- Airflow through cracks: Determined by pressure differences between the crack faces.
- Factors influencing airflow: Crack size and configuration, flow characteristics through crack, pressure difference across the crack.
- Crack classification: Methods to categorize cracks based on component type (straight, L-shaped, multi-cornered).
- Flow regime: Different crack types can result in laminar, transitional, and turbulent flow regimes, affecting airflow calculation methods.
- Large cracks and openings: Flow is turbulent; airflow rate is proportional to the square root of the pressure difference & use the orifice flow equation.
- Small cracks and openings: Flow is laminar; use the Couette flow equation. Intermediate flow situations involve a power-law expression.
- Classification methods: 1) Component type 2) Geometry.
- Specific examples (slots, penetrations, window/door frames): Various building elements and their potential for leakage.
Fundamental of Air Movement
- Driving force: Pressure difference as a result of wind, stack effect, and mechanical ventilation.
- Wind pressure: External pressure gradients directly affect air movement, influenced by building shape, wind speed/direction, and surrounding terrain.
- Stack effect: Differences in indoor and outdoor air temperature result in density differences, producing pressure gradients and inducing air movement.
- Mechanical ventilation: The presence of a mechanical system, like a HVAC system, can deliberately adjust and direct air flow to achieve the desired pressure gradients.
- Total pressure: Wind, stack and mechanical pressures are components that must be combined when calculating total pressure. Often complex, iterative methods are required.
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