If deflectors are used to adjust the cross sectional area to achieve the desired air velocity running costs per kilogram of meat output are constant irrespective of the shed length or width used providing the number of tunnel ventilation fans times the fan capacity is equal to the shed volume. Beyond a width is to length ratio of about 1 is to 12, the tunnel ventilation system will be more effective if the shed length is divided into half and treated as two sheds for design purposes. The fans can be placed at both ends with inlets in the centre or vice versa. Using the previous example and changing the shed length to 204.96m, it would require 18 fans with nine placed in each end. The inlet area is doubled.
Natural ventilation works more effectively with curtains on the sidewall than with shutters.
Shutters interfere with the flow of air across the shed. In wider houses it is necessary to add extra feed and drinker lines which may offset the saving from building a wider shed. Insulation To reduce solar heat load in summer and to contain heat in the house during cold weather the shed must be insulated. In cooler areas also insulate the sidewall area above the curtains. In cooler areas it is cost effective, in terms of insulation costs versus heating costs, to increase the insulation R value to 1.5.