Since my thread has been bumped, I though I'd post a few picture on progress since the last update. I've been slowed by many summer activities and have been tempted to get a little help with the drywall, but I'm committed to making this a DIY project and so have resisted and slowed to pace where I can still enjoy the work.
After the insulation was installed I completed the HVAC system. Following bpape's advice I wanted to enclose a good portion of the duct work inside of a OSB/MDF shell. To partially accomplish this (more will be done inside the theater soffits) I transitioned the 10" pipe duct work into channel made from duct board. I sized the channels to fit exactly into one of the ceiling joist bays so I could encase one length of duct work outside of the theater shell (the rest will be inside the internal soffits). The 13.5"x7" channels that I was able to make out of the 4' wide sheets has a slightly larger area than that of the 10" round duct (87 in/sq vs. 78 in/sq) which means I'm not restricting the air flow. Actually I believe it is a benefit to increase the volume of the duct as it approaches the outlets. Shaping the duct board is pretty straightforward but does require the investment of about $80 worth of cutting tools. Still that is a lot less expensive that having a professional do the install. Here are a few pics that illustrate the process for those that are interested:
Here is a board after the notching is complete. You can see the short section that I made first as a reference before cutting the larger sheets. Basically there are two approaches to notching the duct board prior to folding. You can cut use "V"-grove joints or alternating left and right shiplap joints. The "V" requires a single tool whilst the shiplap requires two: left and right hand orientation. Both also require an end tool. The shiplap joints are considered superior so I opted to that approach.
I purchased my Amcraft cutting tools from Northways Machinery
. Initially I was overwhelmed with the choice of tools but in the end it boils down to a color coded system -- I purchased the 'orange', 'brown' and 'blue' tools for 1" duct board.
Here is the most used notching tool:
All you need to cut the duct board after careful measuring is a straight edge. The tools cut very easily:
After notching and cutting the board easily folds and the remaining flap of foil covering is stapled shut:
All that is left is to apply foil tape over the staples and the section is done. Caution: foil tape gives the worst kind of paper cuts. In fact I'm pretty sure you to cut off a finger if you wanted to! Here are a few completed sections:
Because of some the sharp bends I embedded a couple of strategically placed sheet metal vanes to help the air flow. The vanes were made from a cut up pipe of circular pipe. I'm sure they can be found ready-made but this seems to work just fine:
Creating the enclosure I first sealed the top of the joist bay:
Fitted the duct into the bay after opening up a section to butt up against the end of the round duct section (note that there is a special duct work sealant that was used on all connection points like this to create a good seal):
Finally, when sealing up the ceiling (next post) I was sure to carefully seal the joist bay containing the HVAC duct.
To be clear on my approach, what I'm showing here is not the complete extent of the HVAC insulation. I'm still running another 15'-20' of MDF encased duct work inside of the theater soffits in addition to the section run in the ceiling joists. With this approach I can encase an additional 15' of duct. Since I don't have the HT building experience to quantify the law of diminishing returns I figure the more, the better
This is guide I used to learn how to fabricate duct board: Knauf Assembly Instructions