Exhaust Duct Lines

[bluenose]

I'm renovating a basement bathroom and will be putting an electric brew closet in there. I want to make sure there's a fan for the bathroom usage and an exhaust hood for the brewing area. Both ducts will have to exit the house through the same hole. The total room will be a little less than 8' x 8' x 8' or 512 cf. I've already run a dedicated 30A cable for power.

By searching the net, I've found that for the bathroom activity I should allow for 8 air changes each hour: 512 cf / 60 x 8 = 68 cfm bathroom fan (this seems low to me, but who am I to argue with the internet?). I also found that for a kitchen I would want 15 air changes each hour: 512 cf / 60 *15 = 128 cfm exhaust hood for the brew area. I will probably go overboard on these as I do not want to risk mold/mildew.

What I can't seem to find is what size duct line should I be using, 4" or 6"? I'm leaning to 4" for bathroom and 6" for brew area if there's such a thing as a 4" and 6" Y-fitting.

Does anyone think I'll need an inline exhaust fan for the brew area like rubbertoe did? Should I be able to get a working exhaust hood that'll do the job, or will it be cheaper to rig one up like he did?

Any other comments/suggestions are welcome

[jeffsmith]

I think if you got a hefty inline fan you could likely use the one fan for both purposes.

[jeffsmith]

Also, the nice thing about a remote inline fan in a bathroom (as well as your brewery) is that it won't be nearly as loud as with a standard bathroom fan or range hood.

I've an inline fan installed to serve my upstairs bathrooms and its almost completely silent.

[CorneliusAlphonse]

Little note, I was in an apartment once where they had two dryers vented through the same vent. Whenever our neighbors used their dryer, our apartment would fill up with hot, steamy air that smelled like laundry. Be careful..

[RubberToe]

I think you should considder either one inline fan upstream of the Y or two fans (bathroom style, and inline for the brewery) downstream of the Y, running both when you're brewing to prevent anything coming back to the bathroom fan side.

How long will your duct need to be? I think 4" should be fine and will allow you to use existing duct lines, if you go with a 6" inline fan just step it down.

[sleepyjamie]

might wanna check building codes. not sure if you are allowed to hook up Y adapters to fans from multiple sources. maybe only for things like dryers. not sure.

[jeffsmith]

might wanna check building codes. not sure if you are allowed to hook up Y adapters to fans from multiple sources. maybe only for things like dryers. not sure.

Pretty sure you are as long as you're not dealing with vented gases, you also have to be sure that your fan draws enough to handle both rooms at the same time. For our bathrooms the inline fan upstream from the Y was installed by the builder.

[Maritimer]

I lay out Ventilation systems for commercial buildings for work, I'm not an expert but here is my 2 cents. Also I have no Idea on your house layout.

6" duct will generally handle 100 cfm, it will max out at 150cfm. If your fan has a static pressure rating you can calculate the static in your duct system and size it to match the fan. (I can help you out with this).
Generally, we say 50 cfm per toilet or 2 cfm/ft2 on a washroom, so your 68 cfm is probably on the safe side.

I'd suggest running your bathroom duct and kitchen duct separately. This is the simplest option and it will be the most efficient from an energy perspective. Also it guarantees no cross contamination. If you have to use only on vent on the house connect your ducts together as close to the vent as possible, or tie them both into a common plenum (a larger box) before they exit the building.

RubberToe's suggestion of a single upstream fan is a good option too. However, you will be exhausting more air than you need too (not good in the winter) and smells can migrate between the spaces when the fan is off. You also need to balance the airflow in each duct to ensure your getting the flows you want in each area. In addition to this you need to control the fan from 2 locations.

With 2 fans on a shared duct your going to pressurize one area while exhausting another. Running them both at once isn't the a good choice either as the fans will be fighting each other and your exhausting bathroom air when you don't need to. Alternatively you can add backdraft dampers upstream of each fan, but you run the risk of the smaller bathroom fan not being able to exhaust air when the brewery fan is on.

[Maritimer]

one other note: the commercial code doesn't allow us to combine washroom exhaust with general exhaust except at the inlet of the fan.

[bluenose]

Lots of great input everyone, thx

I should note that the brew closet (what I call the kitchen exhaust) is in the bathroom, so running the two at the same time would just help each other methinks, BUT The way the floor joists run make it difficult if not impossible to get them together anyway. So... two separate lines might be the way to do it

[bluenose]

I just had a brain fart... couldn't I just put a beefed up bathroom fan (160 cfm+)in the bathroom and a non-vented range hood, or is this asking for trouble?

[CorneliusAlphonse]

Even with a strong fan like that, there will probably be a lot of condensation on the ceiling after a brew. I've lived places where I had to wipe the ceiling with a towel after each brew. Haha

[AllanMar]

From http://www.theelectricbrewery.com/ventilation?page=1" onclick="window.open(this.href);return false; (seems reasonable, you are talking about getting rid of ALOT of moisture)

Due to the extra heat and poisonous gases that must be removed, the ventilation requirements are considerably higher with a gas brewery as compared to electric. John Blichmann wrote an article for the November 2012 issue of BYO magazine that summarized ventilation requirements as follows:

Electric based brewery: Divide the element size (in watts) by 17.6 to obtain the required CFM (cubic feet per minute). In our case we use a 5500W element in our boil kettle. 5500 / 17.6 = 312 CFM. We therefore require a fan that can move a minimum of 312 CFM in order to ventilate our electric brewery properly. Fans this size are readily available and reasonably inexpensive.

150CFM through 6" duct seems low, but I don't really know for sure. As he mentioned keep an eye for static pressure ratings, a kitchen range hood usually won't have much of one and won't be suitable for much ducting.

[Maritimer]

there is a free duct sizer program you can download here...
http://www.daikinmcquay.com/McQuay/Desi ... s/Software
scroll down to software downloads, its the first one.

[John G]

I have a brand new 6" 400cfm inline duct fan that I bought for my build and decided to not do the boils indoors, so it's still unused and in the original shipping box. PM if you're interested (or anyone else). I'll post this in the classifieds as well if I don't hear from you.