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Adapting general purpose buildings for pigs

Monday 31st of March 2014

Adapting general purpose buildings for pigs

BPEX, which represents pig levy payers in England and is a division of the Agriculture and Horticulture Development Board, reports on the importance of providing natural ventilation for pig buildings ahead of the Agricultural Buildings Show which takes place in Lincoln on April 3rd. 

Livestock housing is just one of the key issues being addressed at the annual Agricultural Building Show at Lincoln Showground on April 3rd (for tickets and more information see

Many growing and finishing pigs in the UK are kept in straw-bedded pens in naturally ventilated general purpose buildings, the BPEX article notes. The pigs are usually provided with some sort of kennelled area within the building for warmth and an area for dunging and exercise.  

The temperature within the building is not controlled and is usually a degree or two above the outside temperature. In cool weather, the pigs huddle up together under the kennelled area in plenty of straw for warmth. The climate in the UK is generally without any extremes of temperature, however, it is becoming increasingly common to see changes with rapid fluctuations in temperature and humidity in a matter of a few days, rather than more marked seasonal changes. This is putting increased pressure on building ventilation and those responsible for managing it. Extremes of weather, hot or cold, can cause problems affecting pig behaviour and reduce feed conversion efficiency and pig growth rate.

There are two main sources of heat in a general purpose building the pigs themselves and the roof which radiates heat into the building, particularly in strong sunshine.

It is possible to improve the air flow through these large buildings and consequently lower the temperature inside but it is never possible to reduce the air temperature inside the building to less than the exterior temperature.

Ventilation amount can be increased by:

• Opening in the ridge of the building over the ‘standard’ crown cranked ridge.

The size of the opening needs to be calculated and the following information is required:

• Number and size of the pigs being housed

• Height of the building

• Height of the solid side walls below the space boarding.


Usually, the easiest way to create the extra ventilation in the ridge is to remove the ridge cap sheet with the crown cranked openings in it and replace it with a raised ridge cap.

The cap must be high enough off the roof to allow the exhausted air to escape easily which means it must be at least as high as half of the width of the roof ridge opening.   The top purlings often restrict the width of this opening but any opening down the full length of the ridge will be better than those in the standard crown crank ridge sheets often provided with a building.


An open ridge allows heat from the pigs to be removed and is a very efficient way to allow the hot air from under the sun heated roof sheets to escape from the building without heating up the whole space.

Correctly designed, they do not give rise to rainfall entering the building and making the bedding wet. It is also beneficial to increase the amount of air entering the building from the side walls. If any of the space boarding is blocked up either deliberately for the winter or accidently with undergrowth or trees, it should be opened up, or action taken, to ensure the maximum air flow possible. In periods of hot weather, it is beneficial to have sections of the cladding which can be opened up fully; this is particularly important if the building has some solid cladding. The best way to do this is to have hinged ‘drop down’ panels in the space boarding which can be opened as required

The other problem in hot weather is the build-up of heat under any kennelling which can make the pigs dung under it and lie in the rest of the pen. In reality, the kennel is not needed whenever the weather is warm but it often has to be there to give the pigs a warm lying area in cooler weather or at night – so what can be done?

By far the best way to ensure pigs are warm enough in cold weather in a general purpose building is to create a kennel over the lying area. The kennel should be big enough for all the pigs to lie under when they are fully grown. Many kennels are made with a straw layer or straw bales as insulation to keep the pigs warm but, as mentioned before, straw is a definite fire hazard and using it also means it is not possible to adjust the kennel lid height easily. If the lids are made of an insulated ‘sandwich’, it is possible to raise and lower the lids with a winch motor or by hand. In order to keep the pigs warmer under the kennel many farmers close up part of the front of the kennel to keep the pigs warmer when they first go in.

In summary having the correct ventilation within a kennel will improve:

  • Lying/dunging behaviour and in turn improve pig and kennel cleanliness
  • Food intake and growth rate
  • Ventilation amount can be increased by opening in the ridge of the building
  • over the ‘standard’ crown cranked ridge
  • Ventilation can also be controlled by increasing or decreasing the amount of

air entering the building from the side walls

  • Storing straw on top of kennel lids is a fire risk, instead construct the kennel

lid of lightweight framing and cladding with a sandwich of insulation material

such as polystyrene or polyurethane in between

  • Manually control kennel lids to alter ventilation rates
  • In cold conditions close up part of the front of the kennel to keep the pigs

warmer when they first go in.

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