How does roof type affect humidity in the coop?

[aart]

One of the most hilarious examples was a version of the Purina coop built by non other than the experts on Good Old House. They did an excellent job of building what may have been one of the worst coop designs ever concocted.

Boy, that's for sure!!

 

[gtaus]

Didn't quote but what someone else said is correct.You have less humidity because of the elavatef wood floor .The big consern with chicken munure is the build of methane gas ,Any thing placed directly on the ground helps to hold moisture in the ground .The ventalation you have is adequate for you voulme of cubic feet of air space .If your coop were directly on the ground then you would need more.

I had not considered the fact that my coop is elevated off the ground that it would be less humid. I do use a dry deep litter wood chip bedding and thought that was the main reason the humidity remains under control. The gambrel roof type also provides much more volume of air up high compared to the gable roofs I have typically built on my sheds before. I was/am prepared to add more ventilation if needed, but don't see the need for more vents yet.

Ihope you have a moisture proof fabric to protect the floor ,Iuse rubber foofing to cover mine .Remove the frozen poo ,don,t cover it .Finly let me say what a good job you did .Very impressive.

I have a linoleum floor mat on the floor which goes up the sides of the coop for 12 inches. This is to hold my dry deep litter wood chips.

I can remove the frozen poo from the coop, but I thought the whole idea of using the deep litter was to turn that poo back into the wood chips. If I do remove the frozen poo, I'll throw it out into the chicken run so the manure can be used to help break down the 12 inches of leaves I put in there this last fall. That should make some good compost.

Thank you for the compliment on my chicken coop built on an old trailer frame. I did everything myself. It came out better than I had hoped. Not that everything is perfect, but it was certainly close enough for the chickens. I'm pushing 60, so a solo project like that is probably my last big effort. I used to work projects like this with my father, but he passed away last year and I still miss him, especially when I now work on projects that the two of used to do together. But I am thankful for the time we had.

 

[gtaus]

Well, it is really tall.
You've got 8' walls, correct?
Many gambrels have short walls.
If you give me all the dimensions I can calculate the volume in cadd....
...or here's a visual.
View attachment 1986014

OK, took me awhile, but I got the dimensions. The walls are 6 feet tall, not 8 feet. The coop is ~6X12 feet, give a few inches. Here is a snapshot of the online gambrel rafter calculator I used:

What I would like to compare is the volume of that gambrel roof compared to a standard gable roof with a 4/12 pitch, so it would be 12 inches tall at the peak. If I just visualize a gable roof inside this gambrel roof, peaking at 12 inches, it would appear that the gambrel roof is ~3X or more volume. But if you can run the figures through your CADD, that would be great.

Again, I am thinking I have better humidity control because the gambrel roof design is just so much bigger than a standard gable roof. The hot, humid air is dissipated in the larger volume of the gambrel roof. My small vents at the front and back towards the peak seem to be adequate.

 

[gtaus]

@aart, Here in blue is what I would envision the gable roof would look like.

Just eyeballing it seems to be a very big difference. And this is why I am wondering if the roof type plays an important role in humidity control.

 

[123RedBeard]

Go back to post #23, that is the difference if you only change the style.

Now ... if you wanted to lower the peak like in post #34, sure it would be decreased volume, but really has nothing to do with the style ...

Why limit a gable to only 4/12 pitch? A 12/12 pitch would put the peak up closer to where yours is, and give you near the same volume.

The high peak, allows for better temp control and air flow, as the temperature difference between floor and peak is greater, so you can get a better "chimney draft" type of effect, and that is why I think you can get away with a couple of small vents up high ...

Even using your numbers in post #34 ... and your 3 times the volume idea ... that is only the area above the eaves ... all the height from floor to eaves (6') will remain the same, and that volume is more than twice what you have now above the eaves ... so the slight difference in volume above the eaves to peak area is a tiny percentage of total volume ...

 

[gtaus]

Go back to post #23, that is the difference if you only change the style. Now ... if you wanted to lower the peak like in post #34, sure it would be decreased volume, but really has nothing to do with the style … Why limit a gable to only 4/12 pitch? A 12/12 pitch would put the peak up closer to where yours is, and give you near the same volume.

A 4/12 or 5/12 pitched gable roof is pretty standard around here with asphalt shingles. The 4/12 pitch is the minimum building code for where I live. But, yes, if you increase the pitch to that in post #23 it would be closer to the volume of the gambrel roof.

The high peak, allows for better temp control and air flow, as the temperature difference between floor and peak is greater, so you can get a better "chimney draft" type of effect, and that is why I think you can get away with a couple of small vents up high ...

That's what I was thinking. I am prepared to put in larger vents if needed, but so far everything seems to be working out OK.

Even using your numbers in post #34 ... and your 3 times the volume idea ... that is only the area above the eaves ... all the height from floor to eaves (6') will remain the same, and that volume is more than twice what you have now above the eaves ... so the slight difference in volume above the eaves to peak area is a tiny percentage of total volume ...

I understand the volume of air in the lower part of the coop is much more than above in the rafters, but hot humid air rises, so I was thinking the volume above the roosts was very important. When I was thining about the roof types, I was considering a 5/12 pitch gable roof or going with the gambrel roof. Since I wanted a small barn look, I went with the gambrel roof which also offered more volume in the rafters.

 

[gtaus]

Did you build this from plans...or....?

Yes, I used my highly precise CAD program - Crayons And Do-overs (CAD). I had no plans to speak of. I just saw some pictures of barn style chicken coops and liked the design. So I started working with the dimensions of my boat trailer and literally built it from the floor up. The only thing I had never done before was build a gambrel roof, so I used an online calculator to come up with the measurements and angles for that. I also watched a lot of YouTube videos on building sheds and coops and mashed the ideas together until I came up with a working plan. There were a few ideas I had wanted to put into the design, but I decided to finish the project this year. Also, I did everything by myself so I had to be careful not to stretch out beyond my capabilities, both physically and intellectually.

I know some people may be wondering how I managed to put something together more complicated than a cardboard box, but you can learn a lot from watching YouTube videos and asking questions at the local lumber stores where you buy your wood.

 

[Egghead_Jr]

@aart, Here in blue is what I would envision the gable roof would look like.

View attachment 1986984

Just eyeballing it seems to be a very big difference. And this is why I am wondering if the roof type plays an important role in humidity control.

Roof design and pitch has much to do with humidity control. Too steep of a pitch and the fresh air inlet will not mix well with coop air before exiting top vents. A lower pitch will force the air to mix, collect more moisture, making for more efficient use of vents. They can be smaller.

The most efficient roof for air exchange is a single slant. inlets along bottom eave and outlets at top eave. Minimum 3/12 pitch is required. 4/12 or 6/12 pitch is excellent. 9/12 pich and the air is moving fast, creating a barrier-jet stream if you will so not mixing and moving out as much moisture. Low pitch makes the inlet mix well with coop air prior to venting out top end.

The ease of build and low cost of a single slant make them more attractive too. For pure aesthetics a gable can be made for more cost of material and labor. eave vents both sides and ridge vent or two gable vents.

 

[gtaus]

Another source of heat is solar gain from the dark shingle roof and dark red paint. Both of those are radiating substantial amounts of heat into the structure. But that would only show up during daylight hours.....and to some extent, even on an overcast day.

Have you ever compared the temp / humidity difference during daylight hours and again several hours after dark?

Well, the roof is partially covered with snow, but the red building would be soaking up the heat during the day. That is when I have been observing the +5F difference in heat in the coop and outside and the humidity in the coop has been about 8% less inside the coop.

I did compare the temp and humidity after midnight tonight, and inside and outside the coop were the same. So I guess you nailed that one.

 

[gtaus]

The most efficient roof for air exchange is a single slant. inlets along bottom eave and outlets at top eave. Minimum 3/12 pitch is required. 4/12 or 6/12 pitch is excellent. 9/12 pich and the air is moving fast, creating a barrier-jet stream if you will so not mixing and moving out as much moisture. Low pitch makes the inlet mix well with coop air prior to venting out top end.

The ease of build and low cost of a single slant make them more attractive too.

I had considered the slant roof because of ease of build. I had not considered the benefits of air exchange with a slant roof. Good points.