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Ventilation

 

Ventilation 1

Can the maximum air speed of 3.5 m/s be applied also in wide hen houses?

The airspeed of 3.5m/s should be more than enough for a hen house. We recommend that 3m/s will be enough in a well-sealed and insulated hen house.
The airspeed should be the same no matter the house width. In US style houses 1/3 scratch 2/3 slat, and community nest systems, houses will be 12 or 14 m wide. It is very important to have air speed as uniform as possible across the cross section of the house.

Aside from better air circulation, is there any alternative approach to prevent high %RH which is around 90 to 100% at night until dawn?

Unfortunately, the only way to keep the birds comfortable at night with high humidity conditions, is through air exchange.

Is there a calculation for when to start using the cooling pad and at what condition should we start it? We are experiencing high RH. How about the air velocity if we have an average of 2.6m/s for the laying breeder?

I don’t have a calculation for when to start the cooling pads. The longer you can delay using the evaporative system each day, the more opportunity you have to remove moisture. In a breeder house, it is very common to start the pumps at 29 - 30°C. Under most conditions, airspeed range of 2.5 – 3.0m/s should be fine. In a breeder house, it's important to make sure you have the best airspeed distribution. Only start the cooling at maximum ventilation.

 

Ventilation 2

How can we have a comfortable in-house temperature, in high humidity and a high temperature climate?

It all comes back to understanding how the hen or broiler thermoregulates in hot and humid weather. If you increase humidity the hen will increase its respiration rate – panting – to evaporate more moisture from its respiratory tract. If this air is carrying a lot of moisture, the ability to eliminate heat greatly diminishes up to a point where heat builds in the hen, unless we increase air exchange and loose a greater percentage of heat to the surrounding air.
The only option at our disposal is to use an evaporative cooling system which drops ambient temperature to the 28 - 29°C range and exchange the air as quickly as possible to keep the hens internal temperature stable.
We need 3 things:

  • Good ceiling insulation and an airtight house – we want all the air entering the house to pass through the evaporative pads.

  • In hot humid climates, the hens need at least 500fpm (2.5m/s), but I would recommend for a little more – 3m/s or 600fpm

  • Manage your tunnel inlet – curtain or door – to get as much air as possible to move along the slats. Don’t drop your curtain to the fully open position – this encourages most of the incoming air to run down the scratch area. Run some trials to see if you can direct an extra 50 – 70 fpm more down the slats. You will never get perfect uniformity. Closing the curtain or tunnel door too much will increase tunnel fan pressure and reduce average speeds.

How can we manage high humidity in the evening (85-95%)?

The only way is to ensure you have sufficient air exchange. When humidity goes beyond 85% the evaporative cooling efficiency of the bird is greatly diminished. Especially when night temperatures are above 25°C, the most efficient way to remove metabolic heat is through sensible heat loss. With breeders, it is important to have air speeds of 2.5m/s – 3m/s (500 – 600fpm). During hot and humid evenings maintain full tunnel – keep in mind your target experienced temperature is somewhere around 17°C.

How can the dust percentage be decreased inside a pullet house?

It is most likely a combination of the low humidity and high rates of ventilation. If you are restricting the pullets water intake you may consider letting them have 24hr of water. This will likely add some moisture to the areas under the nipple lines and help alleviate the dust conditions. Also, choice of litter plays a big role, products such as wheat straw which has not undergone dust extraction can also be a problem in terms of dust.

 

Ventilation 3

How can I make air speed uniform in 2/3 slatted houses with manual nests?

In a breeder house with 2/3 slats and manual nests we have very limited options to improve airspeed uniformity.
The air will always follow the route of least resistance. The following are some ideas:

  • If you have exposed structural posts on the side wall, consider placing an internal curtain. This will definitely improve the speeds in the 1st meter from the side wall, but is the improvement significant enough to warrant the investment? In Brazil most curtain houses have an internal curtain.

  •  Investing in automated nest systems which are low profile and oriented with the air speed direction is probably your best option in terms of improving air speeds and dropping pressure.

If the wind speed is too low, is it necessary to install a wind deflector?

Yes, the deflector will help to improve wind speed.
There are several key points of wind deflectors,

  • Deflectors can only be used to improve speeds a maximum of 100fpm or 0.5m/s.

  • The deflector should not be closer than 2.75m  (9ft) from the slat.

  • Every deflector you install will add extra pressure. In a production house with many objects such as nest boxes and hoppers the pressure the fans have to work against is usually high.

  • Adding a restrictive deflector will add about 2.5Pa extra pressure, which could mean an extra 20Pa of pressure.

In environmental controlled houses, will placing nest boxes in a longitudinal axis cause a reduction of air velocity inside the house?

The nests lying in longitudinal orientation should reduce some pressure and improve airspeed distribution.
The recommendation is to take an empty house between flocks. Start off by running a simple house tightness test. Then place your nests in a longitudinal configuration, which might require them to be in 3 or 4 rows rather than the traditional 2 rows down the length of the house.
Take some extensive velocity tests across the house and measure tunnel fan operating pressure – as close to the end of the house as possible.
In a house with slats, make sure to adjust the tunnel inlet curtain. A fully open curtain with a low-pressure drop tends to allow most of the air to move to the center of the house. Closing the curtain until you get some better turn at the front of the house, forcing an extra 50 – 70fpm to move down the slats.
This will take a bit of trial and error – but don’t restrict the curtain too much, causing a significant increase in house pressure and a reduction in average speeds.

 

Ventilation 4

During nighttime when the cooling pad is off, do you agree that we could extend the running time of fans to further remove excess heat before the system goes to minimum ventilation?

Yes, certainly running fans through the night is very important, especially with market age birds and high stocking density.  Pushing down target temperatures below normal ensures the house stays in tunnel longer, especially at night after a hot afternoon. Bird activity tends to be low during periods of high temperatures, and they will compensate in the early evening for their drop in feed intake during the afternoon, so ventilation is very important to ensure metabolic heat is removed at night by wind chill. In hot humid conditions a little extra ventilation will not harm the birds, but under ventilation has a far greater impact on performance.

In a tropical country, when can I turn on cooling pad? 28 DOA?

We will only want to use the cooling when we have reached our full tunnel capacity. From about 25 to 28 days when it is hot, the birds will be comfortable with 3m/s or 600fpm.

Is it essential to have a doghouse between fans and light traps?

It will all depend on what operating speed you would like to have for your pullets. If you feel 2m/s (400fpm) is enough, you could just have enough cross-sectional area at the tunnel fan end of the house to fit them in. The big challenge is static pressure, so the larger you make your light trap area the lower your fan operating pressure is.

 

Ventilation 5

What is the ideal duration for cooling pad operation if using an On and Off ratio or would you prefer using the temperature?

My opinion is to let temperature manage the pump. Calculating the pump run time is going to depend on your specific pump and its capacity – how much and how quickly it distributes water across the header pipe. Some new controllers have software that can very accurately control on time for pumps. One of the big disadvantages of using the timer is going to be its effect on pad life. All suppliers will recommend limiting the use of a timer system.  

What is the best position to measure the windspeed? Level of human or chicken?

I would recommend not measuring at bird level. Your readings are going to be lowest and unreliable.
I always measure at about waist height. For the most accurate using tripods with anemometers at 3 positions is the more scientific method and usually done in an empty house.

Could you please highlight more about Sensible Heat Loss?

Any avian species thermoregulates by a combination of evaporative cooling and sensible heat loss. As a general rule, a broiler chicken will partition (essentially split) 60% via evaporative cooling in the respiratory tract which is released into the house in the form of water vapor. The other 40% has to be removed by sensible heat loss. This is done through a combination of convection (moving air), conduction (from a hot surface such as skin to cold surface such as concrete) and radiation (infra-red) to the surrounding air. This heat has to be removed from the house by means of ventilation. The cooler the air passing over the bird and the quicker it does, the more heat the bird can release to the surrounding air. This is what the bird perceives as “wind chill” and referred to as sensible heat loss.

 

Ventilation 6

When the chicks release heat; 40 % as sensible heat and 60% as evaporative, does it happen together or is sensible heat first then evaporative?

Both forms of heat release happen together to balance the bird’s internal temperature. As you would expect these are very general numbers which can be assumed in most situations. So, the sensible heat portion is the heat we have to remove from the house. The evaporative portion is released into the house in the form of humidity.

I have a closed colony house for commercial broilers from day 1 to finish. What are the differences in temperature requirement and air speed?

We don’t have any specific temperature and air speed recommendations for colony houses. The challenge with colony houses is the lack of significant airspeed in the cages and the very high operating static pressure during full tunnel mode. The ventilation and heating systems for colony houses varies tremendously depending on the design.

 

Webinar Replay

 

Hot Weather Ventilation from Day Old to Harvest

Andrew Bourne- WTS
July 1st, 2020

 

Q&A Special: Ventilation

Andrew Bourne- WTS

November 24, 2021