…So take off all your clothes. Or install a heat pump.
Remember “natural convection”? That was the heating system for the second floor of the house when we bought it, according to the seller. Thanks to the open stairway and a couple heat registers placed in the front hall, natural convection worked OK, but the bedrooms were still pretty chilly as the temperatures dipped heading into winter. And if we wanted to keep the convection going all night, we had to run the aging gas furnace that heats the entire first floor just to get a little of that to rise up to the bedrooms.
Since the attic had plenty of space to work, and because natural convection doesn’t help in the summer, we decided to install a heat pump that would provide heated and cooled air to the second floor. Installing a heat pump involves five basic tasks: (1) plopping the condenser unit somewhere convenient outside, (2) positioning the blower in the attic, (3) running supply ducts from the blower to each room and a return duct from the hall to the blower, (4) installing a thermostat, and (5) connecting everything with wiring, coolant lines, and drain lines. Thanks to a connection with an HVAC technician who works with Amanda’s dad, we were able to buy the equipment at wholesale cost from an HVAC distributor. Most of the labor was provided by Amanda’s dad, with some assistance from us, and the technician came by one afternoon to handle connecting the coolant lines.
Relatively speaking, (1) and (2) were a piece of cake: it’s just hauling a couple heavy items into place (although the blower wasn’t quite the “relatively light aluminum box” we were told it would be when we worried about getting it up the rickety attic ladder).
Item (3) took the longest, with a lot of figuring about where the vents should go vs. where they could actually fit. The bathroom vent was particularly troublesome, because the roof structure made it impractical to place it near the window or outside wall (where you usually want the vent), and a mess of existing wiring (both the original knob-and-tube and newer stuff) was hidden under the piles of blown-in insulation. We didn’t end up having to move or replace any wiring there, but Amanda’s dad did replace a portion of the knob-and-tube that ran right through the place where the ceiling needed to be cut for the return duct.
Speaking of which, the return duct was an interesting animal. The ceiling grate is pretty standard, so I figured the box above it would be something you buy at the store too. Nope: you make it.
Armed with some plywood, nails, construction adhesive, and sheets of insulating foam, we built a cube (technically a rectangular prism) that was open on two sides. This got nailed to the ceiling joists above a big hole that had been cut in the ceiling for the grate.
Once the box was mounted, we attached a square-to-round adapter to the square opening. A giant flexible duct then ran from there to the blower. Getting the duct on the circular end of the adapter was a major pain, because the bottom of the adapter was pretty much flush with the top of the ceiling. Joists and wiring limited the amount of space available for hands, and although the duct was flexible, it wasn’t stretchy. You had to get just the right angle to get it around the adapter. I tried and tried and couldn’t quite make it work, so I ended up treating it like a Christmas gift: improvising with lots of tape where there was a small gap (note: you do not actually use duct tape on ducts; you use foil tape).
We will cover tasks 4 and 5 in the next post.