Environmental concerns with owning a RPTV?  

Be aware that some projection sets use liquid-filled lenses. Such a set would not likely survive a hard freeze in usable condition.

The usual term for the problems I think you would have is convergence and focus problems, caused by the mechanical changes associated with the cooling/heating cycles (alignment is a term most often used for electrical adjustments). You might also have a problem with moisture condensation on the lenses or screen (it's not gonna warm up inside the set as quickly as in the room, due to lack of air circulation). Finally, rear projection set cabinets typically are bonded togather with adhesives which may fail in the cold.

Frankly, I would advise against a projection setup in the environment you describe. You might consider a very large screen direct view set like a 36" Sony WEGA instead. Whatever you pick, check out the environmental specs with the manufacturer.