Heathcliff wrote:
Thinking about adding insulation to the attic, which is floored over.
The easiest thing would be to put insulation on top of the flooring.
However, I need part of the space up there for storage. If, say, I put
insulation all around except for an area in the middle, would that
eliminate most of the gains of insulation? In other words, if I leave
20% of the space uninsulated, do I cut heat loss by 80% (of what I
would by insulating all over)? -- H

Something to think about. Part of you house is probably warmer than
others. Often people want their livingrooms warmer than their spare
bedrooms, etc. If that's the case, it might help to insulate over the
warmer areas if you're only going to insulate part of it. Also, I
would stop at wall lines to provide insulation over an entire room, not
stop in the middle of a room.

I'm sure someone can produce tons of formulas saying it doesn't matter,
but I would be that it does and do it that way.