Building Ventilation and Indoor Air Quality

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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?

Using energy when performing air exchanges (D) Signup and view all the answers

What do cracks in buildings primarily affect regarding air movement?

They create opportunities for unintentional air infiltration (A) Signup and view all the answers

What is a disadvantage of using an exhaust ventilation system?

Can cause moisture problems in cold climates (A) Signup and view all the answers

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

The condition of air within and around building spaces regarding pollutants (A) Signup and view all the answers

What might be a direct consequence of excessive air infiltration?

Worsening indoor air quality and thermal comfort (D) Signup and view all the answers

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

Relatively inexpensive and simple to install (D) Signup and view all the answers

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

Causes backdrafting in combustion appliances (B) Signup and view all the answers

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

Anemometry (D) Signup and view all the answers

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

Is dependent on building design (C) Signup and view all the answers

In what climate do ventilation systems typically perform well?

Cold climates (D) Signup and view all the answers

What is an advantage of a properly designed ventilation system?

Enhances comfort by minimizing drafts (D) Signup and view all the answers

Which statement about air infiltration in buildings is correct?

It can draw pollutants into living spaces. (A) Signup and view all the answers

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

Increased need for outdoor air mixing (A) Signup and view all the answers

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

It indicates the type of airflow regime. (D) Signup and view all the answers

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

When the airflow is fully turbulent. (C) Signup and view all the answers

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

A function of crack geometry. (C) Signup and view all the answers

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

Intermediate values between 0.6 and 0.7. (C) Signup and view all the answers

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

Cracks between large and small. (D) Signup and view all the answers

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

It is measured in Pa · s. (A) Signup and view all the answers

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

It determines the flow coefficient. (C) Signup and view all the answers

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

They minimize air infiltrations. (C) Signup and view all the answers

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

A dimensionless value related to flow resistance (B) Signup and view all the answers

Which equation describes the flow rate through a duct?

$Q = A \cdot c$ (A) Signup and view all the answers

What factors can affect the pressure drop along a duct?

All of the above (D) Signup and view all the answers

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

To determine flow regimes, both laminar and turbulent (A) Signup and view all the answers

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

Air infiltration is influenced by cracks and can be analogized to ducts. (D) Signup and view all the answers

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

To differentiate between laminar and turbulent flow (B) Signup and view all the answers

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

The change from laminar to turbulent flow (B) Signup and view all the answers

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

Surface area of the building envelope (B) Signup and view all the answers

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

It is more complex due to varying factors. (D) Signup and view all the answers

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

Pressure difference across the crack. (C) Signup and view all the answers

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

20ºC (B) Signup and view all the answers

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

It is directly proportional to the airflow rate. (B) Signup and view all the answers

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

Cracks can be classified based on their characteristics. (D) Signup and view all the answers

What role does the correction factor play in airflow calculations?

It simplifies the airflow equations. (C) Signup and view all the answers

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

Because it accurately predicts flow at different pressure levels. (D) Signup and view all the answers

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

The air behaves as an ideal gas. (C) Signup and view all the answers

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

By the component type (C) Signup and view all the answers

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

They have similar characteristics. (A) Signup and view all the answers

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

They differ based on the number of panes. (C) Signup and view all the answers

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

They are assigned based on measurement results. (A) Signup and view all the answers

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

It pertains to the behavior of the component. (C) Signup and view all the answers

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

Doors (B) Signup and view all the answers

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

Windows (C) Signup and view all the answers

What aspect is focused on when classifying cracks in buildings?

The component type and behavior (A) Signup and view all the answers

Air Exchange

Replacing indoor air with outdoor air to improve indoor air quality (IAQ).

Ventilation

Intentional movement of air to remove indoor pollutants and maintain good IAQ.