Hi,so far I had had no trouble with drafts,I converted my hen houses first,I think you should be able to control any updraft by the amount of ventilation you have at the top of the house for air to escape.It can't be any more drafty than a chicken roosting on up a tree or duck on a river bank.
None of my new style houses have been through a winter yet mind,but damp and cold on wet bedding has got to be far worse than dry but well ventilated.If draft dose prove to be a problem I guess I could always add a skirt round the bottom.I have set the slats closer together than the ones in the picture about 10 to 12 mm,on both the duck and the hen houses.I have used 2" X 1" slats in the duck house and 2" X 2" in the hen houses.
The best part of it is no more wood shavings to keep getting rid of,it has drastically reduced the amount of waist produced by both my chickens and the ducks.
Now I just wash all the waist away with a hose,into the pond then pump it away,very easy.
It is still very much WIP I am currently re doing the concrete base.
Graham.