Dr Jamie Robertson has spent over thirty years researching farm buildings and their links to animal health and thrive in the UK, influencing change through some of this research.

Jamie was kind enough to sit down with Irish Farmers Journal recently and discuss some of the major gripes he has with Irish and UK farm buildings and how best to rectify them.

Designing around stocking rate

Jamie is a firm believer in designing buildings around their end use and stocking density. “I had a fantastic argument once with someone who was trying to tell me that if your building is so many metres wide, your air outlet in the roof needs to be so many mm wide, which is complete nonsense.

It depends on what type of livestock and how many of them are in the shed, that’s what dictates air outlet space.’’ Air inlet spacing must be twice that of air outlet spacing.

For adult cattle, farmers and builders should work off an air inlet of 0.1m²/head on each side of the shed, or 0.2m²/head, in air inlet spacing, with 0.1m² of air outlet spacing at the ridge.

Example

  • Forty suckler cows in a three-bay double-slatted shed.
  • Air inlet: 40 cows @ 0.2m²/cow=8m².
  • Air outlet: 40 cows @0.1m²/cow=4m²
  • If the side sheeting on each wall along the length of the shed is 1.8m in height, then there is 51.84m² of side sheeting, in which we have to allow for 8m² of air inlet spacing.

    • How to increase air inlet

    Jamie is highly critical of older specifications of vented sheeting, as they lack sufficient porosity to allow adequate air to come into the shed. “Older vented sheeting had a porosity of 5% or less, which wasn’t near sufficient.

    Newer vented sheeting is better, at 15% porosity. Farmers love it because it’s long-lasting, and builders love it as it’s easy to put up.’’

    ‘“What doesn’t work is taking down all your solid or vented side sheeting and then reinstalling them an inch (25mm) apart. You still won’t have sufficient void space for an air inlet, and if you increase it any wider than 25mm you will have uncontrolled air flow.’’

    ‘“Using a gap between the side sheeting and the eave works well as an air inlet, but you must have an overhang to prevent wind-driven rain from entering the building’’.

    At 5% porosity for the vented sheeting, the above suckler shed only has 2.6m² of air inlet spacing, less than one-third of the requirement. Even with new vented sheeting at 15% porosity, the air inlet spacing comes short of what is required.

    Yorkshire vs space boarding

    For Jamie, Yorkshire boarding is the gold standard when it comes to air inlet spacing and controlling airflow in a shed without allowing rain to enter.

    “Too many people confuse Yorkshire boarding with space boarding. It’s simple; Yorkshire is your double row of boards, with the inside row staggered to prevent wind-driven rain, while your space boarding is your single row of boards that don’t prevent rain from entering the building.’’

    Using a 75mm board with a 25mm gap will leave 25% of void spacing on the side of the building. In the above example of the suckler shed, 25% void spacing equates to 12.96m² of air inlet, which is 1.6 times the need of the shed.

    “Too often you stand in the middle of a feed passage, with doors open at each end and the farmer will admire how much air is getting into the shed, but it’s a draught that’s getting in, not air.’’

    Dr Roberston holds issue with many conventional designs of livestock buildings both here and the UK.

    Building height and ventilation

    Jamie does not agree with the idea that building height affects ventilation i.e. that low buildings have poor ventilation. Once there is adequate air inlet and outlet spacing, and the roof pitch is not too low (minimum 15°) then there should be no issue with ventilation.

    ‘’You could have a calf house with a 6ft wall, with a gap between the wall and the eaves (with an overhang) sufficient to provide the air inlet spacing required, and that would be fine, you wouldn’t need any side sheeting on it. The practicality of it is that you wouldn’t be able to clean it out easily, so we raise the roof height to accommodate machinery.’’

    When it comes to air outlet spacing, Jamie feels that many farmers fear excessive rain getting into a livestock building, but he points to the fact that the moisture in an enclosed shed is comparable to the rainfall that will enter into one with sufficient air outlet spacing with an open ridge.

    ‘’I’ve had some farmers tell me that they are really surprised when they removed some roof sheeting over areas such as crossover points in cubicle sheds at how little rain actually enters’’. Jamie said.

    Ventilation tubes in calf houses

    Regarding calf accommodation, Jamie is staunch in his belief that all calf houses require ventilation tubes in order to remove stale air from the building, as calves themselves are too small in size for the stack effect (warm, stale air rising up and out the roof outlet).

    Jamie highlights that removing this warm, stale air, laden with moisture and bacteria can be detrimental to calf health, and removing this from the building is critical.

    In short

  • Historical building designs in Ireland fail to address the needs of livestock.
  • Vented sheeting does not have sufficient porosity in many cases to provide sufficient air inlet spacing.
  • Shed design regarding air inlets and outlets must reflect stocking density, not the width of the shed.