I am considering different options for ventilation on my 36x48 foot barn (in progress now). I'm curious to know if it's wise to have one versus the other, or both. We'll probably do the soffit vents for cool air intake, but Is it possible to have too much ventilation?
I don't think it's possible to have too much ventilation in N.C. We have a three foot tall open clerestory covered by a 4' overhang. It's always pleasant inside the barn even on 100 degree days and we have so little snow that when a bit does blow in it's no big deal. I had originally planned to have drop down doors but have never seen the need to go to the trouble to make them.
I have pictures somewhere but I did a Google search which turned this up first. It's the space between the upper roof, typically over the aisleway, and the lower roof over the stalls. Ours is a taller opening than this with more overhang.
go to the "barn options" page and they have some interior pictures of the aisleway. The clerestory here is the open part right above the stall fronts. Ours works the same way only our barn is wooden and our opening is three feet tall with a four foot overhang protecting it. That opening looks to be about a foot with little overhang over it.
If you are in a warm climate, you may want to move air more aggressively. This could be with a fan in the cupola. We have three ridge vents, which do a real nice job, along with a prevailing wind down the aisle.
We get heat, but not like folks do further south. Our humidity is what gets bad, very high most summers.
Our passive ridge venting moves a lot of air, summer and winter. We have no ammonia smells even when tightly closed in winter, because air keeps changing. Our barn is always cooler than outside with the air moving on even the hottest days. I don't care how cold my barn gets, cold air is good for horses. I just want a good air exchange in all seasons.
My brother builds barns and has put up a number of cupolas that do a lot to move air for cooling. Cupolas he puts up are working both passively and actively with the fans running. Owners love them, really makes a great difference in air flow thru the barns and lofts.
Good timing for this discussion - my husband and I are designing our new barn (which we'll build ourselves). We had discussed ridge vents and cupolas (I wanted a cupola). Mr. CGJ decided he wanted a raised roof over the center aisle (like Tom King described). Mr. CGJ was talking about making drop down doors to close it in for the winter, but I doubt we need that here.
Our stalls have a 6in12 slope so they go from 8' to 14'. The 14' is on the aisleway. Above that is the 3' clerestory and with the support beam above that the aisleway has about an 18' ceiling height. The aisleway is 15' wide so I could use 16' boards for the ceiling joists and have enough on each side to fasten to the tops of the posts. Rafters are made from 2x8's and the 4' overhang on the rafters is tapered down from full width at the aisleway to 4 inches at the outer ends of the overhang so the fascia is not so wide but it leaves the 4' overhang plenty strong.
I used a light colored Fabral metal-lightstone color- on the high roof over the aisleway and architectural shingles over the stalls so it wouldn't be so loud over the horses heads.
I'd do it just like this if I had to do it all over again. I had originally planned to come back later and add drop down doors-that's one reason for more overhang than height to cover-but we haven't seen the need in 29 years.
Everyone that comes in our barn is amazed at how pleasant it is when it's really hot out. Also, we've never had a sick horse.
It's seen three fairly strong hurricanes and during Isabel horizontal water came in one side of the clerestory and went out the other. Everything got wet but not soaked. I'll probably plywood the windward side when we get another hurricane.
I have 2 cupolas and a vented ridge/skylight as well as 2 shuttered vents on either side of the barn. I also left the soffits and about 4" under the rafters open. It turns out, I didn't need quite this much ventilation. I should have taken the hint from my farm name: Windy Spring Farm! We get plenty of ventilation. In the summer it is always cool and pleasant in the barn. In the winter it can get a little too breezy. But I'll take this over stuffy any day. The horses are happy and so am I.