Smoking room advice

I'll start off by saying I am not a HVAC expert but I am an engineer (I could spend a night at a holiday express too if that helps)

Although you do want the room to be as airtight as possible, having a large exhaust fan will help a bit. If you can keep a slight vacuum (relative to the rest of the house) in the room then it will prevent smoke from leaving as air from the house will be flowing into the room through any gaps.

As far as heating and AC, I would think it would be best to keep seperate ducting for the smoke room. If the exhaust fan is large enough you may be able to put an hvac vent in the room, but it will suck a lot of air from the rest of the house and will make it more difficult to keep a vacuum in the room. If it stays cool in the summer then I would have dedicated intake and exhaust ducts that run straight outside and look into an inline heater to put into the intake.

Basically I think an using only the exhaust fan to circulate air would allow you to keep a vacuum and keep the smoke from blowing out into your house. That same vacuum would also draw air through your intake duct. If you have an inline heater that can warm the outside air as it comes in then you can reduce or eliminate the need for a space heater. You would just need to watch the inlet and outlet duct placement. If the inlet and outlet are on opposite sides of the room then the warm air will be drawn across the room, if they are next to each other then most of it will recirc right back out.

I'm not sure how large of a heating system will be sufficient, but if you know the approximate flow rate you'll have through the inlet then you can size a heater based on the flow rate and the desired temperature rise you want (compared to the outside temp). You can probably use the flow rate from your exhaust fan as the majority of the air being exhausted should be coming through your inlet.

I look forward to seeing your progress on this. If you need an extra set of hands to help with some of the construction (or to break it in when you finish) I'll be glad to help, but i'll be in PA for the next 6 months so I may be unavavailable for that time.

I am building my man cave in my garage. So similar things. Heat, air etc. I agree with above do those individual(space heater and window AC) or separate ducting. Make sure you seal the door. Edges in the moulding and one of those runners at the bottom. Your door will be difficult to close but so be it. I would use wood paneling on the walls and seal the edges with appropriate sealer. Drywall will eventually absorb smoke. Of course keep anything cloth out of there. A small purifier and more important is an exhaust.

I'd actually considered doing it in the garage but we have too many bikes and scooters and skateboards and such in there. And I need the other side for my car eventually.