[Aidy]

So the little girl let the cat out the bag, chooks are heading our way, it was supposed to be secret! so time for some coop building, having looked on the net for coops I have priced up a home made diy one, The basics are sorted but I am looking at he ventilation side of things, bear in mind they will be on the plot and not in the garden, although also bear in mind the plot is the other side of the fence. I have just thought of a possible answer, small solar cell connected to a a small 6v leisure battery with an recycled computer fan, whats your thoughts? There will also be a small window type with sliding door.

[IMOmimey]

  you getting THAT MANY?

All you need is something like an inch or two deep, up to a foot long (perhaps like a skinny letterTIVE that this is really high up in the coop, as a draft can be really bad news to choox. I have got 3 very large bore (2") holes in a row, under the eaves of the the roof on adjacent sides, (so wind can't actually whistle through, but air can circulate. If you wanted to get posh, you could make a little sliding door over it, so you can adjust according to weather.

If you are connecting up to lecky,or battery, you will find a light invaluable.

[ehs284]

Would work, but is it worth the complications? You need to design in the air flow; for the solar cell situation you're looking at sunshine = heating so a non-powered system where the sun shines on a dark surface and hot air moves out at the top to be replaced by clean cool air from underneath would work just as well. This could be a covered slot in the ridge, a 'chimney' type black tube at the gable or slots in the high side of a sloping/flat roof. The drop in temperature differential when the sun sets slows the airflow. In winter storm periods you could block outlets if really necessary. If you want a clear on/off system then a greenhouse ventilator prop would do the job. Best of luck whatever you decide.

[joyfull]

If you convert a shed for your coup and roof it with onduline (less space for red mites to live) then you can fill the onduline edges with scrunched up chicken wire (to keep rats out) and this will also act as ventilation. No need for a fan - I am assuming that the hens will have a pop hole and a run for daytime use and not kept indoors all the time.
Oh and welcome Aidy to the wonderfully mad world of chicken keeping 

[Rubellite]

It's as easy as riding a bike, Aidy, and you don't need a Garmin thingummy either