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How Many Ventilators Do I Need?

COMMERCIAL/INDUSTRIAL

  1. Calculate the buildings M³ (Length x Width x Height)
  2. Determine the number of air changes required for the building type (Table 1)
  3. Next calculate the venting capacity M³/h (Table 2)

You will need to know:

  • Typical area wind speed (1m/s to 5m/s).
  • Temperature difference between indoors and outdoors (°C)
  • Roof height

4.   Insert the information into the formula to calculate the total number of ventilator

Table 1

Recomended * No. of air changes per hour
Building Type Air Changes P/Hr Building Type Air Changes P/Hr
Warehouses 3-5 Laundries 7-15
Factories/Workshops 3-8 Welding Workshops 12-21
Gyms/Sport halls 3-8 Animal Housing 10-50
Assembly Halls 6-12 Garages 6-12
Toilets 12-15 Cooking Factories 6-12

*Air change rate must conform to local health department’s code specific to building type.

Table 2

Temperature Difference between Indoors and Outdoors (°C)
3°C Difference / Roof Height 5°C Difference / Roof Height 10°C Difference / Roof Height
Vent Size Wind Speed 6m 10m 15m 20m 6m 10m 15m 20m 6m 10m 15m 20m
200mm Curved Vane 1m/s 180 230 320 380 300 340 410 460 350 580 700 810
2m/s 260 370 500 590 550 680 760 830 590 750 920 930
3m/s 470 720 770 880 730 830 930 1030 800 870 1060 1075
4m/s 720 900 1060 1150 1000 1130 1250 1320 1060 1250 1280 1300
5m/s 1080 1120 1230 1400 1100 1230 1320 1360 1180 1300 1390 1430
300mm Curved Vane 1m/s 270 340 420 490 360 430 500 550 510 720 940 1050
2m/s 320 510 610 760 610 740 840 936 720 870 1110 1220
3m/s 580 930 960 1080 870 990 1100 1200 1000 1090 1280 1340
4m/s 860 1240 1290 1350 1200 1300 1480 1530 1310 1490 1580 1680
5m/s 1310 1480 1580 1640 1450 1490 1630 1680 1520 1670 1810 1910
500mm Curved Vane 1m/s 910 1090 1090 1410 1000 1230 1450 1750 1250 1570 1990 2040
2m/s 1390 1540 1570 1710 1430 1570 1820 2010 1630 1640 2270 2530
3m/s 1640 2246 2080 2210 1840 2010 2250 2420 2100 2250 2710 2860
4m/s 2570 2610 2610 2800 2450 2650 2730 2910 2620 2750 3200 3300
5m/s 3110 3120 3130 3220 3120 3130 3370 3440 3150 3380 3410 3770
600mm Curved Vane 1m/s 1210 1450 1820 2050 1390 1820 2210 2600 1840 2340 2850 3380
2m/s 1900 2050 2300 2600 2090 2310 2680 3059 2360 2780 3230 3690
3m/s 2640 2880 3050 3140 2830 2990 3250 3510 3050 3380 3920 4160
4m/s 3600 3600 3720 4120 3620 3770 3930 4160 3830 4090 4420 4740
5m/s 4320 4450 4530 4880 4450 4580 4710 4870 4600 4860 5130 5395
700mm Straight Vane 1m/s 2136 2542 2923 3289 2491 2964 3468 3988 2905 3457 4045 4651
2m/s 3087 3488 3907 4313 3419 3863 4327 4776 3786 4278 4791 5289
3m/s 4695 5258 5837 6391 5153 5772 6406 7015 5656 6335 7032 7700
4m/s 5887 6475 7123 7764 6346 6980 7679 8370 6841 7525 8277 9022
5m/s 7600 8132 8701 9136 7969 8527 9124 9580 8356 8941 9567 10046
900mm Straight Vane 1m/s 2848 3389 3897 4385 3321 3952 4624 5318 3873 4609 5393 6202
2m/s 4410 4983 5581 6162 4884 5519 6181 6824 5408 6111 6845 7556
3m/s 7825 8764 9728 10652 8589 9619 10677 11692 9427 10558 11720 12833
4m/s 9344 10278 11306 12324 10073 11080 12188 13285 10859 11944 13139 14321
5m/s 11259 12047 12890 13535 11806 12633 13517 14193 12380 13247 14174 14883

 

Formula:

  M³ x air changes (table 1)

venting capacity (Table 2)        =      No. of ventilators Required*

*If this exceeds the amount of ventilators suitable to fit the roof with the recommended spacing of 5m (no less than 3m) then recalculate using a larger size ventilator.

RESIDENTIAL

House Size (M²)
No. of Ventilators Required
 
200mm/300mm
90-120
1-2
130-180
2-3
200-350
3-4

 

If you need any help to work out how many vents and what size and type are required for your building, please do not hesitate to contact us, or please provide your building dimensions of the area you are wanting to ventilate and we will provide a recommendation for you.