zero clearance/factory built fireplaces

[Jethro buckeye]

I'm thinking of installing one of these in my basement in the corner. My walls are block and the floor is a slab. I've heard that code will not allow the flue pipe to have 90 degree turns since I plan on going through the block wall and up the side of the house with tripled insulated SS pipe. They say that I need to go through the block wall with a 30 degree fitting.

Can someone share their thoughts on these factory built units?

Thanks

JethroBuckeye- Go Bucks!