Something to keep in mind for you Cigar room guys..
*Never* put a cold air return in your smoking room. For you guys with basements, the basement will be cool enough in the summer, and you can use electric heat in the winter.
For those of you who don't have basements, you can use "ductless" A/C systems..and again electric heat.
*Venting* When venting your exhaust duct, pick a good location, with no windows above, or no "fresh air" intakes around. What I mean by "fresh air" intakes.. These 90% furnaces have fresh air intakes installed on the outside of your home. You DON'T want your exhaust anywhere near that, or the smoke will get sucked in your fresh air intake..and THROUGH OUT the house! To tell if you have a 90%er furnace if you're not sure, go look at your furnace, and if you see 2 - 2" PVC lines being ran outside..you have a 90%er.
Also remember..that smoke can leave a nasty yellowish stain on the side of your home, so vent properly.
I hope this helps for everyone.,