Building Ventilation and Indoor Air Quality
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Questions and Answers

What is air exchange in buildings primarily concerned with?

  • Removing indoor air without replacing it
  • Preventing air from leaking into the building
  • Renewing stale indoor air with outdoor air (correct)
  • Thermally conditioning only the outdoor air

    • How does air transfer occur within a building?

  • Exclusively through doors and windows
  • Both intentionally and unintentionally through cracks and openings (correct)
  • Primarily by sealing gaps and reducing airflow
  • Only through mechanical ventilation systems

    • What is the purpose of ventilation in indoor environments?

  • To condition the indoor air without replacing it
  • To provide clean air while removing polluted indoor air (correct)
  • To create higher indoor air pressure
  • To limit indoor air movement

    • What energy usage is associated with thermal conditioning of air?

    <p>Using energy when performing air exchanges</p> Signup and view all the answers

    What do cracks in buildings primarily affect regarding air movement?

    <p>They create opportunities for unintentional air infiltration</p> Signup and view all the answers

    What is a disadvantage of using an exhaust ventilation system?

    <p>Can cause moisture problems in cold climates</p> Signup and view all the answers

    Which of the following descriptions best defines indoor air quality (IAQ)?

    <p>The condition of air within and around building spaces regarding pollutants</p> Signup and view all the answers

    What might be a direct consequence of excessive air infiltration?

    <p>Worsening indoor air quality and thermal comfort</p> Signup and view all the answers

    Which of the following is a benefit of exhaust ventilation systems?

    <p>Relatively inexpensive and simple to install</p> Signup and view all the answers

    What is a potential risk associated with air movement in buildings?

    <p>Causes backdrafting in combustion appliances</p> Signup and view all the answers

    Which method is primarily used to measure airflow due to infiltrations?

    <p>Anemometry</p> Signup and view all the answers

    What is a major drawback of relying on random air leakage for ventilation?

    <p>Is dependent on building design</p> Signup and view all the answers

    In what climate do ventilation systems typically perform well?

    <p>Cold climates</p> Signup and view all the answers

    What is an advantage of a properly designed ventilation system?

    <p>Enhances comfort by minimizing drafts</p> Signup and view all the answers

    Which statement about air infiltration in buildings is correct?

    <p>It can draw pollutants into living spaces.</p> Signup and view all the answers

    What is a common consequence of ventilation systems in cold climates?

    <p>Increased need for outdoor air mixing</p> Signup and view all the answers

    What is the significance of the flow exponent in airflow through cracks?

    <p>It indicates the type of airflow regime.</p> Signup and view all the answers

    When is the value of the flow exponent equal to 0.5?

    <p>When the airflow is fully turbulent.</p> Signup and view all the answers

    In the context of air infiltrations, what does the flow coefficient represent?

    <p>A function of crack geometry.</p> Signup and view all the answers

    What indicates that neither fully laminar nor fully turbulent flow is a good match for measured data?

    <p>Intermediate values between 0.6 and 0.7.</p> Signup and view all the answers

    Which type of flow is characterized by being in the transition region between laminar and turbulent?

    <p>Cracks between large and small.</p> Signup and view all the answers

    What is typically true regarding the absolute viscosity of air in calculations of air infiltration?

    <p>It is measured in Pa · s.</p> Signup and view all the answers

    Why is the geometry of the crack important in the context of air infiltration?

    <p>It determines the flow coefficient.</p> Signup and view all the answers

    What is the result of high energy performance building envelopes on air infiltration?

    <p>They minimize air infiltrations.</p> Signup and view all the answers

    What does the Darcy friction factor represent in the context of flow through ducts?

    <p>A dimensionless value related to flow resistance</p> Signup and view all the answers

    Which equation describes the flow rate through a duct?

    <p>$Q = A \cdot c$</p> Signup and view all the answers

    What factors can affect the pressure drop along a duct?

    <p>All of the above</p> Signup and view all the answers

    In which type of flow is the Reynolds number primarily used?

    <p>To determine flow regimes, both laminar and turbulent</p> Signup and view all the answers

    Which option best describes the characteristics of air infiltration in buildings?

    <p>Air infiltration is influenced by cracks and can be analogized to ducts.</p> Signup and view all the answers

    What is the primary role of the Reynolds number in fluid dynamics?

    <p>To differentiate between laminar and turbulent flow</p> Signup and view all the answers

    What does the term 'transition' refer to in the context of flow regimes?

    <p>The change from laminar to turbulent flow</p> Signup and view all the answers

    Which component is NOT involved in the calculation of airflow due to infiltrations?

    <p>Surface area of the building envelope</p> Signup and view all the answers

    What is indicated about the airflow through cracks compared to ducts?

    <p>It is more complex due to varying factors.</p> Signup and view all the answers

    What factor is essential for calculating the airflow rate through a crack?

    <p>Pressure difference across the crack.</p> Signup and view all the answers

    At what standard temperature is the correction factor calculated for airflow through cracks?

    <p>20ºC</p> Signup and view all the answers

    What is the effect of average temperature on the airflow rate through a crack?

    <p>It is directly proportional to the airflow rate.</p> Signup and view all the answers

    Which of the following statements about cracks in buildings is correct?

    <p>Cracks can be classified based on their characteristics.</p> Signup and view all the answers

    What role does the correction factor play in airflow calculations?

    <p>It simplifies the airflow equations.</p> Signup and view all the answers

    Why is the airflow through a crack considered to have a power law relationship with pressure difference?

    <p>Because it accurately predicts flow at different pressure levels.</p> Signup and view all the answers

    What assumption is made when neglecting pressure effects in calculations of crack airflow?

    <p>The air behaves as an ideal gas.</p> Signup and view all the answers

    What is the first method used for classifying cracks in buildings?

    <p>By the component type</p> Signup and view all the answers

    Which characteristic is common among the paths of walls, roofs, and floors in terms of air infiltration?

    <p>They have similar characteristics.</p> Signup and view all the answers

    How do single and double-pane windows differ in terms of air infiltration classification?

    <p>They differ based on the number of panes.</p> Signup and view all the answers

    What does the flow coefficient and flow exponent indicate in relation to air infiltration?

    <p>They are assigned based on measurement results.</p> Signup and view all the answers

    What is the significance of the form of the crack when classifying them in buildings?

    <p>It pertains to the behavior of the component.</p> Signup and view all the answers

    What type of structures display similar crack shapes to single-pane windows?

    <p>Doors</p> Signup and view all the answers

    In the context of air infiltration, which component's path is described as quite long?

    <p>Windows</p> Signup and view all the answers

    What aspect is focused on when classifying cracks in buildings?

    <p>The component type and behavior</p> Signup and view all the answers

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