Garage Ventilation

Overview

Engineering reference data for Garage Ventilation in HVAC systems.

Key Formulas

Sensible Heat

$Q = \dot{m} c_p \Delta T$

Heat causing temperature change.

Latent Heat

$Q = \dot{m} h_{fg} \Delta\omega$

Heat causing moisture change.

COP (Cooling)

$COP = Q_c / W$

Coefficient of performance.

Variables

Application Coefficients Table

Design Examples

Storage Garage Example

For a storage garage with the following parameters:

• Capacity ($c_1$): 10 parked cars
• Mean driving distance ($l_1$): 20 m
• Floor area: 150 m²
• Volume ($V$): 300 m³

Required Air Changes Method: Using a minimum of 4 air changes per hour ($n = 4$): $Q = n V = (4 \, \text{h}^{-1})(300 \, \text{m}^3) = 1200 \, \text{m}^3/\text{h}$

CO Emission Method:

1. Calculate CO emission rate: $q_{CO} = (20 + 0.1 l_1) c_1 = (20 + 0.1(20 \, \text{m}))(10 \, \text{cars}) = 220 \, \text{m}^3/\text{h}$
2. Calculate required supply using coefficient $k=2$ (temporary presence): $Q = k q_{CO} = (2)(220 \, \text{m}^3/\text{h}) = 440 \, \text{m}^3/\text{h}$

Conclusion: The governing design value is the larger one, 1200 m³/h, from the air change method.

Repair Garage Example

For a repair garage with the same vehicle and dimension parameters:

• Capacity ($c_1$): 10 parked cars
• Mean driving distance ($l_1$): 20 m
• Volume ($V$): 300 m³

Required Air Changes Method: Using a minimum of 20 air changes per hour ($n = 20$): $Q = n V = (20 \, \text{h}^{-1})(300 \, \text{m}^3) = 6000 \, \text{m}^3/\text{h}$

CO Emission Method: The CO emission $q_{CO}$ is the same: $220 \, \text{m}^3/\text{h}$. Using coefficient $k=4$ (permanent presence): $Q = k q_{CO} = (4)(220 \, \text{m}^3/\text{h}) = 880 \, \text{m}^3/\text{h}$

Conclusion: The governing design value is the larger one, 6000 m³/h, from the air change method. This highlights that for repair garages, the air change rate requirement is the dominant design factor.

Alternative Ventilation Systems

For larger buildings, a common strategy uses exhaust air from adjacent building ventilation systems as make-up air for the garage. This air, which is already at room temperature (or tempered after a heat recovery unit), is supplied to the garage. Polluted air is then evacuated through openings located close to both the floor and the roof to account for the different densities of fresh air and exhaust gases.

Important Note: Carbon Monoxide (CO) is a colorless, odorless, and highly toxic gas. Local codes and regulations regarding garage ventilation must always be followed, and traffic influence on required airflow should not be underestimated.

References

• Original Source