HVAC tech and I (and architect) are looking at the needed dimensions for the triangular space inside the attic 'pony wall' (5 ft high at the top of the triangle of the pony wall is current design; unit is 21"X40"X30" wxhxd) in order to put in a 5 ton horizontal forced air gas furnace. Length is no problem, but we're struggling with how much clearance from the pitched roof to the air handler/coil there needs to be? Tech wants more clearance, architect is trying to squeeze as much floor space out of this attic buildout as possible. We're in Houston--comments on code would be appreciated as well. Thanks.