Attic Office Addition – Part 5 interior work, Ceiling joists and HVAC.

Once the exterior walls were done and dried in, finishing up the ceiling rafters was relatively easy.

One of the biggest challenges was navigating a heavy LVL into position on the ceiling by myself. In retrospect two 2x10s nailed together would have carried any load just fine but I went for overkill from a safety/strength standpoint.

Speaking of safety…I only dropped it once while on the ladder. …yes dear everything is ok up here. The secret to getting a really heavy board 8 feet above you by yourself is to put a ladder on each end and lift it up to the next step going back and forth until you get to the top of both ladders instead of trying to deadlift with your back and arms.

Putting in the HVAC was something I did twice. Ugh again! If you have never worked with HVAC, tapping into an existing duct and hoping to condition an entire room is pure fantasy. You need to go all the way back to the main trunk and put in a “takeoff boot” with a “damper” for each vent. Otherwise you are robbing one room to pay another and neither has good flow. I originally tried adding duct booster fan which sounded terrible and would need to be controlled with the AC which is doable with a 24 volt relay to the air handler and thermostat control. …but all to have a really noisy fan while I work in my office. I tore it back out. Of course now there were screw holes in it from mounting it to the ductwork so forget returning it. Just doing it right the first time would have been so much better. I know a lot more than when I started.

The other item you will need is a return air path. I put in a grille on one side of the room and the air travels up through the plenum gap between the studs and out another grille on the new office addition side. This is called a High/Low transfer plenum. I did this in an attempt to keep the noise down. (Instead of just having a straight through grille from room to room)

Given the size of the addition, this was not moving enough return air so I also removed a weather strip on the bottom of the existing insulated attic door whigh has now become the new office door. The limitation of the high/low setup is the width of the studs (2×4 at 16 inches on center) can only pull so much air though them where as a direct pass through is only limited to the surface area of the grilles on both sides.

The high/low transfer working together with the undercut of the door now create adequate negative draw to pull the return air back to the system.

Room to room high/low return air plenum
I used a trim router to create a windowsill out of a thin piece of wood I had. Use the best wood you can find for smooth trim results as you will need to patch and sand any imperfections. Or use barnwood and tell everyone you were going for a rustic theme.

Still more to come…Electrical, Drywall, Paint, trim, insulation, floor, final inspection…

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