Would these vents make good ventilation?

It's a 4x8 coop. I plan to add a total of 10 vents, can add more if needed, there is plenty of room and vents. They are placed at the very top, so they aren't near the roosts. Winters aren't too cold here in southeast texas like 40's, maybe 30's if its a really cold winter.
The vents measure 4 by 16 inches. Things didn't go exactly as planned. The wood didn't get cut out before putting up the wall, he forgot. So s hole saw was used to make holes. Which i think might noticeably lower the ventilation. I can get a bigger hole saw and have him make bigger holes if needed. Going to have 6 or 8 large chickens in there if that's needed info.

In Texas I'd think a better choice would be putting in big windows so you could open the coop wide open in the summer. Don't your summers get blistering hot?

Put in all the vents, AND cut large windows in the wall and the door, covered in hardware cloth. You can cover the north and west side windows with plastic or something in very cold blizzards. Ventilation and light! aart's site has very good information about ventilation, and look at Wood's coops for ideas too. Mary

That would normally be true, but I've already got the summer covered. The coop is built under the run, which is 8 ft tall and has a good roof and the run is built under large bushy trees, so its very shaded and stays very cool compared to the rest of the yard. Probably 20 degrees cooler than everywhere else. I'm going to have a 2 or 3 pop open windows, it's more for light, i think i would only keep the larger one open that is going to be on the back side during summer. The coop stays dark, even with the cleaning door open which is 2 1/2ft by 4 ft. I have a battery powered lantern in the coop I use for now.
I am more worried about the vents because they are the only ventilation the chickens will have during nighttime, when they poop a lot. I don't want them breathing in nasty air.

Why only keep the one window open in summer? If you're worried about air quality then just leave them all open and you'll get a nice cross breeze.

I agree to install all the vents. I'd put them on opposite walls, not on the prevailing wind side. For winter, as long as wind doesn't blow in onto the roosting area, just adjust the amount the windows are open.

I wouldn't waste any time or $$$ on those vents. They are nothing more more than dust/dander collectors. Cut some BIG holes (Like 2X3') into the coop, and get some fresh air in there. If you want to cover those little holes, put some hardware cloth over them, and frame with wood, to cover the edges. You're in Texas, the chickens will easily handle that mild winter weather. Open the coop up, not only for fresh air, but to get some sunshine in there. No way you should need a lantern, to see in there. Chickens like sunlight, they are not moles.

Well, the vents had been in the garage for years, he wanted to use them for something, so that's why we used them. I know they like sunlight, lol. I didn't expect it to be that dark, but then again it is a heavily shaded area, i should've made the connection. It isn't pitch black, you just need a light to see good early in the mornings and later in the evening. You can see fine when it gets to be later in the morning until 4 or so, with all the trees and the fence, i guess the sun has to get to a certain point before it shows. I'm going to have at least 2 pop open windows, probably 3. There is going to be a large one on the back side and another large one on the front and maybe a smaller one near the nest boxes. We could cut holes and put hardware cloth over them like you said, seems easy and efficient enough, but i thought mosquitoes would bother them & spread diseases or something, so i was going to have the windows so at night i could close them and mosquitoes wouldn't get in. There is the draft issues to.

In the summertime, in Texas, I don't think it would be a good idea, to close up the coop. It's going to be hot enough as it is, without all the ventilation being shut off. I've seen Texas coops, where practically the whole thing is hardware cloth, with maybe a couple of solid walls back by the roost area.
I live off a branch of the ChesapeakBay, we have mosquitoes, that will eat you alive (Not to mention the greenhead flies), and my birds have never seemed to have any problems with them.

I live in Port Arthur, TX. During the night, it usually stays in the 60's or early 70's if its really hot, but since the coop is built under a run with a roof and trees is should stay a lot cooler than that even at night. Thats why we are building a new coop, because it stays like 20 degrees cooler under all those trees than where there current coop is. We get some rather violent storms sometimes, a small coop and with big holes like that, i think there would be to much draft. I could just walk my lazy self all the way back there and close/cover them if a storm came through though and leave them open the rest of the time if its to hot though.
I won't worry about the mosquitoes, because I have relatives in Louisiana and their mosquitoes are much worse there, and becasue you're in an even more watery area, they are probably a lot worse.
I was thinking i could get him to take the vents off and cut a 8 inch gap all the way around the coop, and then staple some hardware cloth over it. The roosts are at 2ft and take up the whole left half of the coop. So i can't put vents there because of draft, i could put a little window there though for natural light. There will only be 8 chickens in there but, there are three, 4ft long 2x4s. So i could remove 1 to make more room for holes. The nest boxes are on the right side, up against the back wall (inside the coop), they take up 3ft. They are removable so i move those over to the side wall. So there if i cut a big whole in between the next boxes and the roost, it wont be too drafty?

Your coop is 4X8'. If one of the 4' end walls face south. You could remove the sheathing, and have a hardware cloth screen wall. That would vastly improve ventilation, and add some free light in there. Now, if the south facing wall is one of the 8 footers, you could open half of that and screen it, and end up with the same improved result.

I have found, if the coop is properly ventilated, after it rains, and some blows in, the coop will dry in a short time. (Unless you live in the pacific northwest, and it rains for weeks, then the coop will most likely, stay kinda wet). Also, the hardware cloth itself blocks a lot of the rain from blowing in. My coop is pretty much wide open. Open wire covered front wall (South facing), along with 3X3' side windows, that, when opened, are only covered with hardware cloth screen. The upper windows are hinged at the top and open out. So they keep most rainfall from coming in. When all the windows are opened for warm weather, I never run out and open and close them, according to what the weather may do, rain forecast or not. If it rains and some blows in, the coop always drys out.

Drafts can be a problem. But don't get too hung up on them and worry. They can have a little air movement in the winter. Especially in your mild winter climate. As long as they are not living in some kind of wind tunnel, with the air blowing their feathers up, there is nothing to worry about. They are like little furnaces, wrapped in down.