MBR Sheet Metal
P:+61 8 9309 5000
mail@mbrwa.com.au
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AIR MOVEMENT REQUIREMENTS FOR BUILDINGS

The effectiveness of the MBR Ventridge is not dependent on wind power, however wind will further increase the extraction rate.
The most suitable ventridge is dependent on the number of air changes required per hour and the size of the building.

To calculate the suitable ventridge size the usage of the building should firstly be determined and then the relevant number of air changes specified (see table 1). For example a building that is being used as a boiler room will require approximately 25-40 air changes per hour compared to 4-8 air changes per hour for a warehouse. It is then appropriate to calculate the ventilation rate.

FRESH AIR INLET

To enable natural ventilators to function at their rated capacity, fresh air inlets should be provided as close to the floor level as possible.
MBR manufacture a full range of fresh air inlet louvres for this purpose. MBR require that the total free area of inlet represents 1.5 times the throat area of the ventilator and that it be so positioned so as to ensure uniform distribution.

SUGGESTED AIR CHANGE RATES FOR TYPICAL BUILDINGS EXHAUST CAPACITIES
Types of Buildings Air Changes per hour
Public Halls
Assembly Halls 15-20
Auditoriums 10-15
Bowling Alley 10-20
Churches 10-15
Classrooms 15-20
Restaurants 20-30
Theatres and Cinemas 15-20
Toilet Rooms 12-15
Poultry Sheds
Brooder Houses (factor of bird numbers)
Hen Houses (factor of bird numbers)
Incubator Rooms 8-10
Kitchens and Food Processing  
Bakeries 25-40
Breweries 20-30
Commercial Kitchens 20-30
Packing Houses 15-20
Power Plant and Associated Buildings  
Boiler Rooms 25-30
Power Houses (factor of power steam loss)
Pump Houses 12-15
Sub-Stations (factor of power loss)
Transformer bays (factor of power loss)
Clothing Industries  
Dry Cleaning 30-40
Dye Houses 40
Laundries - ironing 30-40
- washing 20-30
Heavy Manufacturing Industries  
Engine and Motor Rooms 15-20
Forge Shops - cold 16
- hot 25-40
Foundries - moulding 40-50
Pouring and Core Room 60-70
Furnace Rooms (factor of heat loss)
Galvanising Shops 12-20
Heat Treatments 30-40
Machine Shops 6-10
Rolling Mills 30-40
General Industries  
Motor Garages 10-12
Light Manufacturing 10-12
Warehouses 4-8
T diff Exhaust k (C) Effective Stack Height Wind Velocity m/s
    0 1 2 3
3 3 0.31 0.66 1.01 1.37
  6 0.43 0.79 1.14 1.5
  9 0.53 0.88 1.24 1.59
  12 0.61 0.96 1.32 1.67
  15 0.68 1.04 1.39 1.75
6 3 0.43 0.79 1.14 1.5
  6 0.61 0.96 1.32 1.67
  9 0.75 1.1 1.46 1.81
  12 0.86 1.22 1.57 1.93
  15 0.97 1.32 1.68 2.03
9 3 0.53 0.88 1.24 1.59
  6 0.75 1.1 1.46 1.81
  9 0.91 1.27 1.62 1.98
  12 1.06 1.41 1.77 2.12
  15 1.18 1.54 1.89 2.25
12 3 0.61 0.96 1.32 1.67
  6 0.86 1.22 1.57 1.93
  9 1.06 1.41 1.77 2.12
  12 1.22 1.57 1.93 2.28
  15 1.36 1.72 2.07 2.43

The above velocities are indicative only and when used in the formula shown will determine approximate ventridge throat sizes.
 

 

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