bcorps
Songster
Building my own coop is a continuing learning experience. Heck, everything in my life is a learning experience. It’s how I’m wired. Sometimes it can be exhausting, but when I go to bed every night, I know I did something that day.
I’ve been fascinated by my little flock’s seeming imperviousness to cold. They rarely show any signs of discomfort, in temperatures that manage to turn me into a whiny whining whiner. Yesterday, while I sat in my chair shivering (but enjoying their antics nonetheless), I noticed them just standing ankle deep in the snow…when dry ground was mere inches away. It’s like they don’t even feel it. Which is not to say they don’t appreciate a nice cozy, toasty human to sit on from time to time. My favorite, Little Miss parked her feathery bottom on me while I was in that chair, and proceeded to tuck her head under her wing and take a nap. I was so hesitant to interrupt her, I suffered a bit longer than I probably should have. I did exact a bit of an ironic toll. When my hands started to feel the sting of potential frostbite, I tucked them under her belly, where I reclaimed some of the heat she had leeched from me. Turnabout is fair play, Little Miss!
Back to my coop. I started wondering just how cold they can take it without cutting me out of the freezer camp process, and what can be done to help make their coop more hospitable without resorting to a dangerous heater, if they need help at all. I have also heard that chickens (at least the more Winter-friendly breeds) don’t really start suffering until it gets down to -20F in the coop. That is a frightening number, as it would kill just about any human on the planet in an hour. Let’s hope I never have an opportunity to test that hypothesis! I’ll stick to more reasonable situations (I hope).
Essentially, any thermodynamic problem can be solved if you know what your heat inputs and outputs (losses) and insulation qualities, and temperature deltas are.
A quick bit of research on the interwebz produced a heat output figure: 10 watts per hen. So my ten chickens, as a single unit, are basically on the cuter end of the spectrum of 100-watt heaters. I would imagine that the boys, being quite a bit larger, generate even more, but for the sake of this write-up, I’ll just consider them all girls. How rude of me!
I’m sure most of you have seen the term “R-Value” when it comes to insulation. Basically, all materials have an R-value specific to them. Given that my coop (and most in general) is constructed mostly of ¾” plywood, I will again, for simplicity’s sake assume my coop is a big plywood box.
The equation for R-Value is:
We can re-write it as Delta-T = R times flux.
The plywood naturally is the barrier.
Heat flux is defined as power/area…watts/m^2.
The R-value for ¾” plywood is 0.94.
My coop is essentially a 4ft x 6ft x 5ft box. Which is 148 square feet. Punch that into a converter, and you get about 14 square meters. So flux will be 100 watts divided by 14 square meters, or about 7.
Which leads us to the maximum temperature difference between the outside and inside 0.94 x 7 = 6.5 K. ("K" is for "Kelvin", sort of a fancy pants more scientific temperature scale akin to Centigrade or Celsius.
One Kelvin equals 1.8 degree Fahrenheit, so we also have to multiply by that factor.
Which gives us about a 12 degree Fahrenheit difference between inside and outside.
So what do we do with this new knowledge?
12 degree difference is for a basic plywood box. (Mine is probably a little bit better than that. All of the 2x4's make a substantial portion of it thicker and so forth.) The Omlet coop they are in right now while I am building is much smaller (lower flux), and has double insulated walls (higher R-Value), so I know it is doing a much better job of keeping them warm than my new coop will…unless I add a few things. The Omlet is probably keeping them at least 30 degrees warmer than outside air. I have no doubt of it.
But if I were to add just a single inch of pink XPS foam (which has an R-Value of 5) between the roof rafters (I could conceivably add even 3 inches there), on the bottom of the floor, and in select areas where they can’t tear it up, I could probably get my “average” R-Value up to 2 or 3. This would increase my coop temperature difference up to 30-ish degrees Fahrenheit. This additional insulation will cost me probably 20 dollars, but will pay for itself in my anxiety reduction over the Winter.
I don't think this is "spoiling" or "coddling" them. I doubt very much my chickens will be weaker for "only" having to sleep in temperatures as low as 30F.
I also don't think this is going to cause overheating issues in Summer. My coop has a tremendous amount of screened window surface for ventilation, so I can leave it open on those HAWT 90F nights; they should be no more miserable than they already would be.
I’ve been fascinated by my little flock’s seeming imperviousness to cold. They rarely show any signs of discomfort, in temperatures that manage to turn me into a whiny whining whiner. Yesterday, while I sat in my chair shivering (but enjoying their antics nonetheless), I noticed them just standing ankle deep in the snow…when dry ground was mere inches away. It’s like they don’t even feel it. Which is not to say they don’t appreciate a nice cozy, toasty human to sit on from time to time. My favorite, Little Miss parked her feathery bottom on me while I was in that chair, and proceeded to tuck her head under her wing and take a nap. I was so hesitant to interrupt her, I suffered a bit longer than I probably should have. I did exact a bit of an ironic toll. When my hands started to feel the sting of potential frostbite, I tucked them under her belly, where I reclaimed some of the heat she had leeched from me. Turnabout is fair play, Little Miss!
Back to my coop. I started wondering just how cold they can take it without cutting me out of the freezer camp process, and what can be done to help make their coop more hospitable without resorting to a dangerous heater, if they need help at all. I have also heard that chickens (at least the more Winter-friendly breeds) don’t really start suffering until it gets down to -20F in the coop. That is a frightening number, as it would kill just about any human on the planet in an hour. Let’s hope I never have an opportunity to test that hypothesis! I’ll stick to more reasonable situations (I hope).
Essentially, any thermodynamic problem can be solved if you know what your heat inputs and outputs (losses) and insulation qualities, and temperature deltas are.
A quick bit of research on the interwebz produced a heat output figure: 10 watts per hen. So my ten chickens, as a single unit, are basically on the cuter end of the spectrum of 100-watt heaters. I would imagine that the boys, being quite a bit larger, generate even more, but for the sake of this write-up, I’ll just consider them all girls. How rude of me!
I’m sure most of you have seen the term “R-Value” when it comes to insulation. Basically, all materials have an R-value specific to them. Given that my coop (and most in general) is constructed mostly of ¾” plywood, I will again, for simplicity’s sake assume my coop is a big plywood box.
The equation for R-Value is:
We can re-write it as Delta-T = R times flux.
The plywood naturally is the barrier.
Heat flux is defined as power/area…watts/m^2.
The R-value for ¾” plywood is 0.94.
My coop is essentially a 4ft x 6ft x 5ft box. Which is 148 square feet. Punch that into a converter, and you get about 14 square meters. So flux will be 100 watts divided by 14 square meters, or about 7.
Which leads us to the maximum temperature difference between the outside and inside 0.94 x 7 = 6.5 K. ("K" is for "Kelvin", sort of a fancy pants more scientific temperature scale akin to Centigrade or Celsius.
One Kelvin equals 1.8 degree Fahrenheit, so we also have to multiply by that factor.
Which gives us about a 12 degree Fahrenheit difference between inside and outside.
So what do we do with this new knowledge?
12 degree difference is for a basic plywood box. (Mine is probably a little bit better than that. All of the 2x4's make a substantial portion of it thicker and so forth.) The Omlet coop they are in right now while I am building is much smaller (lower flux), and has double insulated walls (higher R-Value), so I know it is doing a much better job of keeping them warm than my new coop will…unless I add a few things. The Omlet is probably keeping them at least 30 degrees warmer than outside air. I have no doubt of it.
But if I were to add just a single inch of pink XPS foam (which has an R-Value of 5) between the roof rafters (I could conceivably add even 3 inches there), on the bottom of the floor, and in select areas where they can’t tear it up, I could probably get my “average” R-Value up to 2 or 3. This would increase my coop temperature difference up to 30-ish degrees Fahrenheit. This additional insulation will cost me probably 20 dollars, but will pay for itself in my anxiety reduction over the Winter.
I don't think this is "spoiling" or "coddling" them. I doubt very much my chickens will be weaker for "only" having to sleep in temperatures as low as 30F.
I also don't think this is going to cause overheating issues in Summer. My coop has a tremendous amount of screened window surface for ventilation, so I can leave it open on those HAWT 90F nights; they should be no more miserable than they already would be.
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