A Ventilation Equation

[Egghead_Jr]

Quote:
Where I live, I couldn't count on wind as a factor in determining adequate ventilation because most of the time there isn't any wind at all! I built 1 square foot of ventilation per bird up high over roost level, then additional ventilation (almost 3 square feet) per bird down lower that I can open or close as needed. This August during our 100 degree plus heat wave, this passive ventilation kept the coop no warmer than the outside air, which is what I was aiming for.

My climate/ situation is oppisite than yours, so was looking for enough venting without too much artic air blasting on the chicks. Here in Northern New England it can hit 10 below for a week or more. Hopefully I'll have substantial heat gain for January-Febuary. I'll have to post a pic as the sunny weather yesterday gave the oppurtunity to finish. Well, almost, screwing the roof on and hinging the nesting box roof today. The clean out door I can open for few hours a day to stable temps for July-August here.

 

[Egghead_Jr]

Quote:
Right, dynamics of large buildings is different, as in my vents are not going to freeze over. You found the dairy barn standard, many large animals (needing 28cfm per cow) in a large building during winter snow fall. 7 chickens are not going to exhale enough to freeze over my vent holes. The roof 6 inch over hang I provided ensures snow and ice/ leaves wont block them either

As far as dynamics of small openings sure. It's a kin to water flow in pipes. 1/16 of inch is disgarded due to surface tension.

I'll state for the last time that the equation is vallid and ony works for a system of eave to Gable/ridge venting with the proper slope. It is a minimum. NOT a gable to gable only system, this would be a different system and far less efficient. This equation provides a bare minimum, more is better, but the system allows for venting withiout large heat wasting orafices-inlets to blast artic air on my birds. I'm using it due to location in North New England. Drilling holes is what I did and accounted for surface tension/construction error with the excess holes above minimum area calculated. Many would have a continuous eave vent of 1/2 inch or so. It's easier that way when constructing to have your end wall slightly short (i.e. a continuous vent along the eave). With proper overhang these will not get obstructed by snow and ice.

 

[purpletree23]

This is really too scientific for me. I have the same question a Egghead Jr. I also live in New England on a hill that I lovingly refer to as Lambo Field in the winter. I have a sweeter heater for heat and it works just enough to take the -20 degree chill out of the coop during the worst weather.

How do I balance venting the moist air without causing a draft? The coop has 3 windows that I can crack open a bit but where should I make the air outlets? Maybe I'm wrong but if the air is vented at the roof line wouldn't the warm air go out also? I have to get this figured out soon. In the mornings the windows are moist and it's only going to get worse.

I use the deep litter method and turn it over frequently so it can dry out if wet. The next few days here are going to be warm and I'll open the windows and door to make sure everything is dry. My bones tell me that a large snow storm is coming by the first week of December.

Any advice is truly welcomed.

 

[blueberrychickens]

I too am in New England & while all that math stuff makes my head spin, here's what I'm gonna try. My coop has plenty of ventilation, so I plan to open one of the 4 vents & stuff it w/ some news papers. I figure that way any moisture will be able to escape the coop & it'll keep the cold breeze off of the girls. On days that are going to be stormy out, I'll just keep the vent cracked a bit & not lock them in tight. So far on the frosty mornings there has been little condensation on the windows which are single paned. The vents are covered by the eaves on the roof of the coop, the only way snow or rain could get in thru the vents would be if it snowed or rained UP! Here's a picture....

You can see the vents above the nest boxes that my DH was working on. There are 2 on each side. Then my main door opens in 2 pieces, & we have a locking screen that goes on the top part of the door for use during the day time. Ooodles of ventilation there!

 

[purpletree23]

Sounds like a valid solution. One concern I have though. What will you have covering the vent besides newspaper? I'm just thinking that a raccoon would be able to get in. I have hardware cloth over my windows and if anything tried to pull it off they would have very bloody paws. I cut the hardware cloth to fit just beyond all sides of the window on the outside and used heavy duty staples to attach it to the wooden frame. My husband said that we have Fort Knox and not a chicken coop but funny thing is he locks the door at night and I usually don't.

If you already have something like this just ignore my rambling.

Hello from Merrimack, NH

 

[blueberrychickens]

Oh, of course there is hardware cloth on the vents! The vents also have doors that swing down to cover them in the event of nasty weather. We too have Coop Knox! there isn't any critter getting in there w/ out a saw! I really need to post pics of the coop now that it is all done & finished (for this year anyways!)

Merrimack huh? Did you get snow this week??

 

[Egghead_Jr]

Well, it's been 3 days and I'm liking what became of things so far. As in this morning (I was home and not last morning that was 18 F) when I opened the coop door and then checked the ceiling and walls for any sign of frost all was dry and water was good; yet had to brake out the waterer's ice in run. Now it was only 24 or 26 F this morn yet when I went back to pick up the eggs a few hours later the water inside coop had froze over. So, all is well for my own peace of mind to provide the min air venting that will still keep heat in the coop. The coop door is a 12x12 inch opening. That door opened for less than 2 hours froze over ther water inside by 8:30 am yet that water was fine when I'd opened the door at 6:30 am.

 

[LynneP]

Egghead Jr.- Every coop is an experiment in progress. The damp winter air here is a challenge and the wind can switch direstions in a heartbeat, with the Nor'Easter being the worst scenario.

blueberrychickens- for a tiny investment you may be able to buy a replacement vent which will open and close. Most hardware stores have them and often the feed mills and farm stores carry them.

It's always an experiment isn't it? I'm a math & science type but my formula is simpler- if the hennies are fluffed, I close something down and if they're comfortable I leave them alone and there are places in the run and coop where they can always find shelter from wind! Winter is certainly tricky though. Our climate is much like yours, except we get a longer stretch of frigid weather in late Jan or early Feb. For me, it's more about the water and I use an electric dog bowl now that there are no chicks in the coop. This week I've been teaching my old hens how to use a clear plastic pop-door barrier. One of them likes it so much I estimate she has been in/out a hundred times just for the heck of it.

 

[patandchickens]

Quote:
I did not just find the dairy barn standard; I know perfectly well what the commercial chicken-barn numbers are as well.

I'm telling you what ACTUALLY HAPPENS IN BACKYARD COOPS, not infrequently, when you have cold winters and teeny vent holes. Yes, they certainly CAN frost over. Not theory; observation.

Clearly you want to do it your way and are still in the phase of believing that mathematical models are more important than seeing what actually happens, so have fun.... just dress warmly when you are out there in a January cold snap cutting bigger holes in your coop, hopefully *before* getting any actual frostbitten combs :>

Pat

 

[patandchickens]

Quote:
Please see my ventilation page (link in .sig below) for a fuller explanation of all this stuff.

However, to answer your specific questions briefly: In a cold-winter area you don't want BOTH inlets and outlets in a backyard-sized coop; you just want ONE opening (or set of openings), decently sized, high atop the wall(s). Air will go BOTH IN AND OUT of the opening. Really really. While being as minimally-drafty as possible. Yes, warm air goes out also. That is actually what you WANT in a way, b/c the warmest air is the stuff carrying the most moisture. Obviously your coop will be a bit cooler with proper ventilation than if you shut it up tight, but chickens are not affected by cold as much as by *humidity* at cold/cool temperatures, and tend to get frostbite at much milder temperatures if their air is humid. So colder is a perfectly acceptable tradeoff for *drier*.

See the above-linked page for more.

Good luck, have fun,

Pat