Yes, you absolutely do CERTAINLY need good ventilation, even in the winter. (Please note I live in Canada myself
).
The best arrangement is to have a good large amount of ventilation, high on all 4 walls, with flaps or sliders or whatever so that it can be securely closed off when not needed on that side. (This lets you adjust it to accommodate winds from any direction, and alter the amount of ventilation depending on your needs and on night temperature).
There are two reasons why you want the ventilation high on the walls:
1) the chickens aren't there themselves. You really don't want a cold draft aimed right at the chickens, for their health. And
2) that's where the warm air is. I understand that, as your dad says, this sounds backwards if you want to keep your chickens comfy
but the thing is, the main point of ventilation is to remove MOISTURE. Warm air carries more moisture than cold air. Getting rid of warm air, in a winter coop, gets rid of more moisture, and that is Good.
What you will do is keep the ventilation adjusted (in terms of which vents are open and which are closed) so that you have as much open as you can without having freezing wind coming in. On super cold nights when the chickens may have trouble staying warm-- and remember, chickens are generally good for some ways below freezing, as long as the air is DRY not humid and there's no draft on them -- then you can temporarily reduce the ventilation further overnight if you really have to.
Hope this helps, have fun,
Pat