this is an odd question? Manufactures' data sheets only deal with sidewall venting clearances, Our local code book deals with chimney height clearance..Have your contractor research it and give you an answer prior to installation..
“Now the freaks are on television, the freaks are in the movies. And it’s no longer the sideshow, it’s the whole show. The colorful circus and the clowns and the elephants, for all intents and purposes, are gone, and we’re dealing only with the freaks.” - Jonathan Winters