HIGH?

The Poultry Bulletin - - INTERNATIONAL NEWS -

I Wn­creas­ing side­wall height doesn’t sig­nif­i­cantly in­crease heat­ing costs

hile there’s a com­mon mis­con­cep­tion that poul­try houses with higher ceil­ings have much higher heat­ing costs than those with lower ones, this sim­ply isn’t true. Rather, heat­ing costs have much more to do with in­su­la­tion and ven­ti­la­tion.

For a mod­ern, totally en­closed broiler house, rais­ing the height of the side­wall from two and a half me­tres to three me­tres will re­sult in heat­ing costs ris­ing by less than 5%. This is be­cause even though a 20% in­crease in side­wall height in­creases heat loss through the side­walls by 20%, the side­walls rep­re­sent a very small per­cent­age (6%) of the total heat loss from a poul­try house. So, in­creas­ing the rel­a­tively small amount of heat loss through the side­walls by 20% or even more would not have a big im­pact on the total heat­ing cost. By far the big­gest source of heat loss is ven­ti­la­tion, ac­count­ing for around 70% of the total cost of heat­ing a totally en­closed poul­try house; in­creas­ing side­wall height would have no ef­fect on the amount of fresh air birds re­quire.

This isn’t to say that higher ceil­ings can’t be re­sult

in higher heat­ing costs. In open ceil­ing houses - houses with­out at­tic spa­ces - it tends to cost 10% or more to heat than dropped ceil­ing houses, not be­cause the ceil­ing is higher but rather be­cause the in­su­la­tion value is a half to a third that of a dropped ceil­ing house.

Greater sur­face area

An open ceil­ing house also tends to have a greater sur­face area than a dropped ceil­ing house. Gaps be­tween in­su­la­tion boards and at the peak of the house tend to make an open ceil­ing house looser, fur­ther in­creas­ing heat loss from the ceil­ing. But in a dropped ceil­ing house, if the side­wall height is in­creased, the ceil­ing doesn’t change and so heat loss through the ceil­ing re­mains the same. The only fac­tor con­tribut­ing to higher heat­ing costs is ex­tra heat loss through side­walls, which is min­i­mal.

There are sev­eral ad­van­tages of higher ceil­ings dur­ing cold weather. Cov­er­age area of ra­di­ant heaters in­creases as ceil­ing height in­creases. When a ra­di­ant heater like a tube or a brooder is in­stalled at a rel­a­tively low height, floor tem­per­a­tures will tend

to de­crease rapidly as you move away from a brooder. This re­duces the num­ber of chicks in a house that re­ceive some mea­sure of ra­di­ant heat. Con­versely, when in­stalled high above the floor, cov­er­age area is in­creased and floor tem­per­a­tures tend to de­crease more slowly as you move away from the brooder or tube heater. In wider houses, it can be a chal­lenge to in­stall ra­di­ant heaters at an op­ti­mal height. The rel­a­tively low mount­ing height sig­nif­i­cantly re­duces cov­er­age of tube ra­di­ant heaters, and can lead to fairly high floor tem­per­a­tures di­rectly un­der the tube heaters. Hav­ing a higher side­wall in this sit­u­a­tion could help to im­prove floor con­di­tions across the width of a wide house.

Cold air

It is also im­por­tant to re­alise that as ceil­ing height de­creases, bring­ing in fresh air dur­ing cold weather with­out chilling the birds be­comes more dif­fi­cult. Dur­ing cold weather, the air space above the birds is used es­sen­tially as a mix­ing cham­ber. Warm air pro­duced by a house’s heat­ing sys­tem and the birds them­selves rises and col­lects near the ceil­ing. Cold air→

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