One of the most common mistakes in design of a hen house is not having enough ventilation.
But, you say,
I bought a commercially made hen house. Surely it must have the right amount of ventilation?
Sadly No. Quite a few hen houses sold commercially haven’t got adequate ventilation.
In this video I want to discuss the principles of hen house ventilation.
Before we get into the details,
firstly let’s consider why ventilation of the hen house is so important for chickens.
We all like fresh air to breathe. Just like us, chickens get oxygen from the
air that that we breathe in and get rid of carbon dioxide in the breath that they breathe out.
Typically, fresh air contains about 20% oxygen and that’s just about ideal for us and for chickens.
If the oxygen concentration in a room gets below 16%, humans will feel exhausted and mentally
confused. If the oxygen concentration in a chicken house gets below 16%,
the chickens will become lethargic. Since chickens normally have a high respiration rate,
they use up oxygen more quickly than humans. If the oxygen concentration in a room
or a chicken house drops below 6%, both humans and chickens will die.
So, yeah, breathing fresh air is kind of important.
A well-managed chicken house shouldn’t smell.
Without good ventilation and hygiene, your chicken house will smell of chicken poop,
including methane and sulphur, both of which can be lethal at high levels.
For the benefit of your neighbours as well as your chickens, and to make your chicken house
a pleasant place for you to be in and around, you want it to smell nice. (fresh as a daisy?)
The ideal temperature for adult chickens is between 20 and 23°C (68 – 75 °F).
Like us, they can stand a few degrees hotter than is ideal,
but they don’t cope well at all with heat. And chickens can’t cool down by sweating.
When they get hot, they need to pant out the excess heat in their breath.
If the air in their chicken house is already hot, they can’t get rid of that excess heat
efficiently. If they are managing to get rid of some excess body heat on their breath,
that is raising the temperature inside the chicken house, and so the chicken house gets even hotter.
If it gets above 32°C (90°F), the chickens will suffer from heat stress, and that can be fatal.
Dust in a chicken house consists of fine particles of straw or whatever you use for bedding,
lots of bits of old feathers and dander, and dried up particles of poop and bacteria. All of that is
irritating to chickens’ delicate respiratory systems, and makes the chickens vulnerable to
airborne disease organisms. Good ventilation helps keep dust levels low and the air clear.
Chickens don’t sweat but they do breathe, and their breath carries
a lot of moisture into their environment. And chickens do poop – a lot. And chicken
poop consists of 55-83% water! That’s partly because chickens don’t urinate – their kidneys
filter out waste water but then it’s removed from the body in the poop rather than pee.
Even without any moisture coming into the chicken house. from rain or leaks,
there’s a lot of moisture building up in a chicken house
All that moisture encourages rot, rust, condensation, molds, mildew and the
growth of bacteria that make your chickens sick. You want to ventilate that moisture out of there.
As droppings break down or bedding decomposes, ammonia is released into the air. If you’ve ever
smelled ammonia, you know that even a small amount is pretty unpleasant. Ammonia irritates your eyes,
sinuses, throat and respiratory tract, and it’s the same for chickens. And that irritation can
quickly lead to respiratory damage, blindness, and eventually death. Not a pleasant way to go.
If you can smell ammonia, the level is too high to be comfortable for your chickens.
And remember to take a sniff near floor level – that’s where the ammonia is
coming from. And chickens are not tall – their noses are close to the floor.
Except for immediately after you’ve cleaned the chicken house, there will always be a small amount
of poop that is decomposing and releasing ammonia. You need air movement to move that ammonia out.
So, ventilation is very important, but I’m sure you’ve heard that drafts are bad.
What’s the difference between ventilation and drafts?
There are several answers, but I like to say that ventilation moves air gently,
and generally vertically from floor to the roof, and right throughout the chicken house.
A draft on the other hand is air blowing briskly and directly onto the chickens.
In hot summer temperatures, a cooling breeze might actually be pleasant but in cold weather
drafts will chill the chickens, leading to illness as well as increased food consumption.
Drafts can come from air gaps in the construction of the chicken house walls
as well as poorly placed windows or doors.
You can check your chicken house for drafts by holding a lit match or candle where the
chickens perch. If the flame is blown out, it’s too drafty. If the flame wobbles a bit, that’s
probably about right. If the flame is perfectly steady, there might not be enough ventilation.
Now maybe you live in a really cold climate. Your tendency might be to try to keep your
chicken house as warm as possible, maybe insulate it, and seal it up tight to prevent any drafts.
But this could be a mistake – you do need ventilation, even in very cold climates,
in fact ventilation is especially important when the temperature is cold.
That’s because of water vapour.
Chickens have a high heat generating metabolism,
and their downy under-feathers are excellent insulation as long as they are dry and unruffled.
On cold nights the chickens fluff up their feathers, huddle together to share body warmth,
and tuck their bare feet underneath them on the perch. Most chickens can withstand temperatures
several degrees below freezing as long as it’s dry and there isn’t a draft blowing on them.
But that dryness is important. At low temperatures, the air can’t hold so much water
vapour, and the relative humidity is higher than it would be for the same amount of water vapour
at a higher temperature. In cold weather it’s actually warm moist air that is most dangerous,
because the warm air can carry more water vapour, until it comes into contact with a cold
surface, where the water condenses and lowers the surface temperature even more.
The chickens’ downy feathers insulate them just like woolly gloves insulate
and protect your hands from winter cold. But naturally wet feathers aren’t such
good insulation, just like your hands will get cold if your gloves get wet.
Warm air needs to rise upwards and from there exit the chicken house,
taking its load of moisture with it. So it makes sense that especially for cold climates,
ventilation of the chicken house should be high above the chickens’ heads, well above perch level.
The only part of the chicken not covered by feathers are its comb and wattles.
If moisture condenses on their cold comb and wattles, the chicken will suffer frostbite.
Frostbite is injury caused by the flesh freezing and you can recognize it because the dead flesh
turns black. Naturally enough, the breeds of chicken with large combs and wattles
are especially prone to frostbite. Frostbite is painful for people and
almost certainly painful for chickens too. If your chickens have frostbite,
it’s probably not because your chicken house is too cold, but because your chicken house is too
damp and drafty, because you haven’t cleaned out sources of moisture such as manure, because
there are cold drafts blowing directly onto the chickens, and the ventilation isn’t adequate.
Heat is far more dangerous to chickens than cold. When it’s hot, chickens will try to lower their
body temperature by holding out their wings away from their body, spreading out from each other
along the perch (assuming you allowed enough perch space for them to do that), and panting.
A poorly ventilated chicken house will hold in the heat and can turn into an
oven without you realizing it. It’s a good idea to check the temperature inside your chicken house,
maybe with a thermometer.
The principle of high vents is the same, so hot moist air will rise up
and exit out of the chicken house. In addition, openings on opposite walls
can create a cross flow and very effective ventilation. But unless the temperature is
exceedingly high, there should not be a draft blowing directly onto the chickens.
Once again dampness and humidity are the enemy. Higher humidity makes it feel hotter and difficult
to breathe. Good air flow can help keep the humidity down as well as the temperature.
In summary, in hot weather, ventilation serves the purpose of removing moisture,
dust, ammonia, gases and smells, plus it also helps to lower the temperature.
So now that you are convinced of the value of ventilation,
exactly how much ventilation should a chicken house have?
Plenty of people on the internet and books will give you an answer,
but actually I believe the answer is, It depends. Quite a lot of variables are involved:
o Is your climate hot or cold? o Is the humidity high or low?
o Do nights get cool? o Is it windy?
o Is the chicken house located where it’s sheltered from winds or exposed?
o Is it in shade or direct sun? o How insulated is it?
o What is the roof made of? o How high is the roof (volume
of air matters more than floor space) o Do you use bedding that is naturally
moist (like deep litter) or is the floor dry? o How frequently do you remove the droppings?
o How crowded with chickens is the chicken house? o What breed are the chickens? (big
comb & wattles in cold / heavy breeds in hot)
So that’s a bit complicated. To make it simpler, we could just say that except
in cold weather or if it’s drafty, you can almost never have too much ventilation.
So the golden rules for ventilation are: - include as many large openings as possible,
- and make them adjustable so you can open or close them as
weather and wind direction indicates, - always include high vents to allow
warm moist air to exit, - unless your climate is very cold,
include some cross ventilation, - but avoid drafts blowing directly
onto the chickens, - keep out the rain
and other sources of water, - and keep the manure cleaned out.
If you want to know whether your chicken house has enough ventilation,
the simplest way is to just go inside your chicken house frequently.
- Do you see any condensation? Or frost? - Is the bedding on the floor damp?
- Does it feel hot inside? - Is it drafty?
- Can you smell ammonia? - If it’s none of these things,
it just feels comfortable to you and your chickens look happy, then you probably have it about right.
In my recent videos I’ve been sharing the process I’ve been going through to design
and build my Ultimate suburban hen house. In the next one in the series, I’ll look at how
I applied these design principles to my situation to ensure my hen house has adequate ventilation.
Look out for that video, coming soon. Bye for now.