Hole for Exhaust Port

I’m getting ready to install a vent system for a new electric brewery I’m constructing. I bought an ActiveAir 6” inline fan and speed control. (one of these http://www.plantlightinghydroponics.com/active-air-400-cfm-inline-duct-fan-p-2754.html) I’ll have about a 5’ straight run from my hood, then a 90 degree turn and about another 2’ of venting before it ports outside. I have a nice 4” hole saw, so I was thinking I would cut a 4-inch hole and use a reducer to drop to 4” right at the outlet. I’ll be drilling though aluminum siding and I believe there is just one rim joist I have to go through. My question is, being I have to drill a hole either way, am I better off just drilling a 6” hole? It’s kind of scary drilling that big of a hole in the side of my house. 6-inch hole saws seem hard to come by and very pricey, which is also why I am hesitant to do this. I’m guessing airflow will be pretty good even with the 4” reducer. I’ll be brewing mainly 10gallon batches. Any thoughts would be appreciated.

Proceed with the 4". It's not going to restrict the flow much, it will just increase the velocity. You might even run all the ducts in 4" and place the 4x6 reducer closer to the fan. It will save you in ductwork and shill provide plenty of ventilation. I assume you won't be running this brewery 24/7?

Thanks for the input. I'll have to consider the 4" lines. It's in my basement, and I'm 6'5, so any additional headroom is always appreciated. I currently only brew about once a month so it won't be running that much.

What kind of hood are you hooking that into? I'm doing a little searching for something cheap and simple.

I framed out the hood with 1X2 pine, then used 1/8" birch ply on the exterior. I had some 1/2" styrofoam sheet lying around so I put that between the 1X2 framing on the interior and then covered the whole interior with plastic PVC sheeting ($18 for a 4X8 sheet from home depot). I stained the exterior with an oil based stain and then applied 2 coats of oil based varnish. I plan to post some pics of my build, I just haven't gotten around to it yet.

Sounds cool! I'd like to see how you did yours.