And after it was hung - at the center of the hallway ceiling:
Feeders will extend from this "trunk line" to supply air to each room. It's like the spinal cord of the house, running along the vertebrae of joists, giving comfort to each space. I do think of this house as a living organism.
In my original drawings I assumed this duct would only have to be 8 inches in diameter. But it turned out to have to be 12 inches - which puts the bottom of it slightly lower than the 4 x 12 beams on each side. I was fine with this spatially, but soon I realized that the inswing windows along the hall might hit the duct when opened. They swing just below the beams, so I knew they would be at least very close to the slightly lower duct pipe. I told my mechanical contractor to open the windows once the duct was hung. It wouldn't be a total disaster if the duct was too low; we would just have to move it about 6 inches away from the glass to let the windows swing all the way open. Of course that would mean that the duct would not be in the center of the hall, which was pretty important to me visually.
Thankfully the windows were able to swing all the way open without hitting the duct - though with less than 1/4 inch to spare. That was so close that the cables used to hold the duct to the joists had to be moved so the windows wouldn't catch on them, despite being less than 1/4 inch around. So to swing these windows all the way open fast and watch them barely clear both the beam and the duct is something of a breathtaking exercise in faith that I didn't really intend.
The air handler housing is seen beyond in the photo below. The duct bending to the right goes to the kitchen and bedrooms, the duct on the left supplies the Great Room.
Where the hall meets the Great Room's brick wall, the duct will bend up and go through a small opening above the doorway, and into the attic space around the skylight well:
The duct will be concealed in the Great Room, in other words. The idea to expose the duct in most of the house goes along with the overarching goal of being honest and truthful about how the building is made. Necessary parts of the building are brought into view and fixed into order. But the Great Room is first of all about holiness, expressed as perfection, orderliness, cleanliness. Everything that hangs out in the rest of the house gets neatly tucked away in the Great Room. The messiness of a string of different-sized rooms along a hall, the lines of joists in the ceiling, the duct pipe, is all behind us when we enter the Great Room. The focus then is the pure symmetrical shape of space, the orderly brick and wood skins defining it, and most of all the light from above.