New Feed to Old Attic

My daughter and SIL bought a nice, old, 2-1/2-story home in Davenport, Iowa. I suspect the floorplan is typical of the era (1920s?). It is basically square with a full, unfinished basement; two, full, finished floors above grade; and a third level: the attic. In the attic are 2 or 3 modest dormers on a four-sided HIP roof.
The previous owners did a LOT of work to this fine place, including the attic. Planked *YEAR* ago (oak?), the floorboards were subsequently drilled and insulation was injected. That, of course, will complicate any upgrade to the rooms room below, but we'd deal with that later.
Right now, the ONLY electrical up there is an old pendant light hanging from its knob-and-tube wiring controlled by an SP switch at the bottom of the stairs. That's it. No outlets.
I investigated pulling-up new power from the basement to the attic using the void that MIGHT exist in the enclosure around the sanitary stack and brick chimney. Some, if not all, of this space is already occupied by added/replacement copper water lines to the second floor bathroom that was remodeled some few years ago. I am doubtful that we'd have much success adding MORE stuff to this chase. Even if we were successful, it would probably be tight and even possibly damaging to the cables pulling them up.
I believe it would be "better" to make an EMT run from the basement to the attic up the outside of the house. This would be close to and parallel to the main service mast on the rear of the home.
Of course, I want to install a conduit of sufficient capacity to accommodate all potential future demand from the attic, including the possibility that we would rewire second floor bedrooms and bathroom below the attic as well as the demand should the attic be finished, including a window air conditioner (15k BTU/240VAC). The second floor SEEMS to be adequately cooled by the newer central air conditioning so capacity up to the attic to accomodate AC window units in the second floor (below) are NOT a given at this time.
Should I run a 3/4-inch tube or 1-inch?
(Yeah, I know about percentage fill of raceways and boxes but have forgotten much and am intimidated at the prospect of finding the appropriate reference for this and making the necessary calculations. I'm asking for a GOOD guess, please.) TIA!
--
:)
JR

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On Tue, 29 Aug 2006 02:17:59 -0500, Jim Redelfs

Run 4-wire 10-GA to a sub-panel, and branch out from there.
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