The chimney effect is real that is why in ye olden day homes had tall chimneys so in the winter it made lighting and maintaining a hot fire much easier and in the summer it drew cool air through the home.
If I had a flate lide I would want at least a nipple taller than the edge of the barrel so water would not collect on the top and fall into the drum but I have a weber dome so its not a problem.
Lg Spicewine on trailer
Weber charcoal grill
2 ugly drums, semi retired
Bbq toolbox, formerly Chargrill smoker
My wife has gas, its a Brinkman.