Thanks to Miller for forwarding along this photo, sourced from finlandia sauna.
Indeed, this photo is worth a thousand words. 8′ ceilings MAY have their place with a triple bench system, in health clubs and spas, yet even this is a stretch. There are too many wasted cubic feet to heat.
If you have 8′ walls in your ceiling, consider dropping down the ceiling. It can be done! Check out this earlier post.