Can we clarify the problem?
This is what I see on the link you posted:
Unless I’m missing something the text looks to be perfectly centred within that border box. If you look at the capital T and the Capital H then the space above and below is exactly the same. Obviously ascenders and decsenders may poke up and down depending on font etc but the text is perfectly centred.
The alignment looks exactly the same to me as a blank page with browser defaults albeit font, fons-size and line-height will all be different but the text will sit in the same place.
The space the text sits in is defined by the line-height which is 1.4 in the foundations css as opposed to
normal which is 1.2 in most browsers. However this doesn’t affect where the text sits in that line-box and to some extent will depend on font construction as leading and half-leading may be built into the font itself.
If I look at the html outside of foundation then I see this:
Which is actually not as well centred due to the odd px line-height and there is one pixel more space under the capital H that at the top.
If you can specifically point to the appearance you would like then maybe we could work to a solution. I think however that I may be looking at the wrong problem