Overhead duct in roof space or hang from ceiling?

[Matt Putnam]

I'm getting around to unfitting my shop at last. I've walled off the car area in our freestanding 4-car garage so I'll have a 20' x 30' space plus a 10' x 8' adjoining area for lumber storage. Ceilings are 10'.
I'm going to move my DC into an adjacent room that will be walled off from the shop space and plan to run 6" duct into the shop space.
My question is around running the main trunk line into the shop. I originally planned to just hang it from the ceiling (I guess I planned that as I've normally seem it there) but I believe I could run it between the roof trusses in the roof space and pop through for the machine connections. I plan to do OSB walls and ceiling.

Any pros or cons on the two options?

[Jim Andrew]

You can make U shaped brackets, and screw them to a 2x2 fastened under your ceiling members pretty easily to hang the pipe. Much easier to change when you need to then climbing around in the attic.

[Jim Becker]

If you have convenient access to the truss area, then routing your duct work "up there" and only bringing drops through can make for a very nice, clean-looking shop environments. It also provides more headroom with less places for ambient dust to settle. :) Same goes for any overhead electrical.

Jim is correct that making changes in a cramped space is more work, but honestly, I'd opt for that if I had the ability. (my shop upstairs is floored for storage, so I couldn't do that except behind the knee walls which wouldn't cover much of the need)

[Ben Rivel]

I screwed cheap pine 1x3's to where ever the 6" main duct had to go and then I screwed quick release hose clamps (LINK (http://www.oneida-air.com/inventoryd.asp?item_no=SCOLLECT45)) spaced a about 2 feet away from each other to hold the ducting up. I did the same thing down and along the walls for the drops. Worked amazingly easily and extremely strong. The Oneida ducting (LINK (http://www.oneida-air.com/category.asp?Id={0B4E2053-B182-4867-93F9-3602C0D1960D})) I used feels like you could hand from it after I got it all mounted up.

[John K Jordan]

Matt,

I ran my 6" ducts through the roof trusses above the ceilings (stand-alone shop) and brought down drops for the machines. Here is a section under construction.

351091 351092

This took more planning (and careful engineering to avoid compromising any truss!) but I'm happy with the result. I put inspection/cleanout access near ceiling hatches. All ceiling panels are 1/2" ply held up with screws in case of an unfortunate need to rework anything up there.

I made most of my bends with 45 or 22.5 deg fittings to minimize sharp bends. The cyclone is in a sound-insulated closet mounted with brackets to an outside wall so it won't transmit sound directly into the shop. The big air compressor shares the closet space. I return filtered air to the shop through a large baffled duct. I mounted controls, disconnects, bin-full alarm, and wireless remote receiver outside the closet in the main shop for visual monitoring and easy access. Be sure to allow plenty of access to empty the bin!

JKJ

[roger wiegand]

It's way easier to get at if you get a blockage in the system if it is not enclosed. (I used to try to collect the long strands from green woodturning-- big mistake.)

[Tim Bueler]

One possible con of putting the pipe in the rafters depends on your climate. If you live in a heating climate, and if you are heating your shop, and if you are piping that heated air through unconditioned space, you run the risk of condensation on the outside of the pipe. Higher levels of relative humidity in the attic = more condensation. When I was building houses we were required to insulate the bath fan ducts. That was western WA State, very moist. In the early days people would call complaining their roof was leaking and it was coming out of the bath fan. 99.9% of "leaks" were fixed by insulating the ducts. Not always easy after the fact. :(

[John K Jordan]

It's way easier to get at if you get a blockage in the system if it is not enclosed. (I used to try to collect the long strands from green woodturning-- big mistake.)

I put the accessible cleanout/inspection plugs on the ends the straight runs.

As for condensation, loose insulation blown over the ducts seems to work.

JKJ