Double FFS: height = altitude - elevation. It really isn't difficult, and makes absolutely no difference whether you use QNH and add elevation, or use QFE and don't: you're still at the same level relative to the runway you're going to land on. And it has nothing to do with the question.
I've just looked at an FAA airport directory incidentally; they list "TPA" traffic pattern altitude: and list two numbers the first is pattern altitude, the other is above airport elevation (in other words, circuit height!). QNH or QFE in effect, even if they don't use those terms over there. For example, it lists Palm Springs, which has a runway elevation of 477ft...
TPA - 1977(1500) large acft, 1477 (1000) small acft.
Just what I could do with here!
G