You need to compute the capacity required.
Total volume
10 * 12 * 8 (8ft ceiling) =960 cubic ft.
Required 8 changes of air per hr.
The fan needs to move
(960/60) *8 = 128 cfm (cubic feet / minute)

HTH

Thanks - Since the electrician is "grumpy" - I think I'll check with the builder to see what size fan is being put in. I did notice that it is larger than the powder room fan, it's also not fully installed, so maybe I can climb up there and see if it has the specs listed on the interior portion..

Ok I looked at the fan box and it is showing only 100 cfm

So right off the bat my fan is too small or I need to add another one..But, the electrian isn't gonna believe me.

If my ceiling is 9 ft. and I have o1 fan at the end (not near the shower) how big of a fan should I have them add near the shower.

It's gonna be a battle to get them to add one - but, I take very hot showers and with the steam shower I can't imagine that a fan at the far end would be able to draw all that steam up up and away..

Please help me calculate for another fan...

It's your house and your money. He doesn't have to believe you, he just has to do it. I regret every single time I let a contractor/tradesman bully me about work at my house.

Total minimum exhaust requirement is 144 cfm.

If you want to keep the first fan, the second would need to be able to remove ~50 cfm.

It probably makes more sense for the fans to be on the same circuit. There should not be any problems to bear the load. The contractor should be able to calculate the total load.

The other question is whether the noise from both units would be acceptable to you.

Jeanie - With all due respect, this isn't your electricians home it's YOURS and grumpy or not he works for YOU and is obligated to do what YOU want. Don't ask him, TELL him,"I want a second fan, period" And then show him where you want it. If it were me, I'd probably include that if he's not able to do that, then there's always the option of hiring someone else who can. Don't let him push you around just because you're a woman. When it comes to this kind of stuff, follow your insticts and don't compromise, you'll be sorry in the end if you do.

I just want to chime in with the crowd who says it's YOUR home, and you should not be bullied by people YOU are paying to set up the place where YOU live!

David - Thanks for doing the calculations for me.
I'm fairly certain that my builder supplies/pays for the exhaust fans. So that's probably why his electrician is being "skimpy and cheap" with the fans.

I know that I need to be more in control of what I what and just make my point - I need to stand my ground and let them know that they cannot "sale" me on thier ideas. I made a lot of concessions even building in this plan and the house plan that I choose. It seems everything that I want is an issue and that they feel I don't need it..

I'm going to search the internet and see if I can find a page that says how to properly size a fan to a bathroom and print it out for my builder/electrician. Maybe THEN they will believe me!

I'm newly separated and yet I still feel like I have to have a man's approval for my decisions!!! haha Here I thought I was done with that part of my life..

You want the vent to be near the primary source of moisture, which will be your steam shower.

There are fans that can be installed in an attic space, referred to as "remote fans", they are designed to vent one or two ceiling grills. You could have one grill outside the steam shower and another, perhaps even smaller, over by the toilet.

Remote fans are tremendously quiet and usually the ducting is easier to run to them, so you have fewer bends and restrictions. That results in less static loss through the duct and your fan will be moving more air.

Static loss for a typical installation is about 20-25%, so if you wanted roughly 140-150cfm I'd recommend a roughly 200cfm fan.

Were I doing your bathroom I'd recommend a 190CFM remote Fantech PB190 fan with the grill located just outside the steam shower door.

I'd also put the fan on a timer switch, something like this.

Mongo's solution is best, but if your builder puts up an issue with a remote fan, use two of the Panasonic brands. They are not only quiet, they STAY quiet, which the Broan/Nutone brands don't. We have what was their largest fan in 2003, for our 7x13 master bath, and a smaller one in our main floor bath. They are excellent quality!

Mongoct, you answered a question I needed to research for my DH. I told him I wanted a single remote fan to exhaust the two side-by-side baths we are redoing. Well, adding one and redoing the other. So your links are what I will give him.

And Jeannie, don't be intimidated. This is where you take charge without losing control of the project. I had the same issues when first divorced too, and oh boy do I know how you feel. Do not make threats, you know you can change electricians and do not need to telegraph your intentions to anyone. Keep your cards close to your chest, and stay cool. NEVER LET THEM SEE YOU SWEAT, as they say. Look them in the eye and see if they can look back. Go for it.

Here is a link direct to the booklet at that site Mongoct gave. If you view pages 3 and 4 of the brochure, it will cover the subject of two grilles using one fan motor.
Link is below.

Here is a link that might be useful: Fantech pdf brochure

If it were my bathroom, I'd size the fan between 200 to 240 cfm and place it around the same location as Mongoct suggested.

I'd also rather have one hole in the ceiling.

It's also preferable to get things done right and to your satisfaction the first time.

Jeannie. Never threaten. It takes away the surprise.

Jeannie, take heart. When men told me I should not be doing the job I was doing, I told them if they paid my bills, then they MIGHT try to tell me what to do.

I listen to advice, but realize that ultimately it is my responsibility to make the call. Don't worry about hurting their feelings, they really do not care what you think and won't give it a second thought. Make YOUR choice.

I am not an expert on the exhaust, but just want to support you on avoiding intimidation (been there, done that).

Have your plan laid out in writing with what you want. Include the calculations and expert advice you have received here. Tell your electrician you will be adding an additional fan and tell him the brand and location where you want it, then say "this is my expectation so I am looking to you to make it happen, please let me know when you will be able to update your plans with this request." Hang in there, don't back down. :-)

I am very interested in Fantech for our master bath. While the walls and ceiling are still open, I want to make some final decisions. Since Fantech doesn't make heaters, which heaters have you used with them?

Thanks.

bnevens, I put a fantech in my bath remodel and love it. I installed a wall heater from Stelpro that I am very happy with. I chose it because 1. it was made in Canada and not China and 2. It has dual controls, so I can leave it on low all the time and it keeps the chill off the bathroom via convection heat. But when I want it to be really toasty for a shower or bath, I can turn the timer on and it controls a forced air fan for really fast heating, turning off automatically. (it then returns to the setting I leave on the thermostat for the convection heat). It is nice looking, good quality, etc. There are probably others, I just happened to stumble on this one and like it a lot.

Here is a link that might be useful: Stelpro heaters.

Best pay attention to the ducting too! This can be especially important if the run is a long one or has a lot of bends.

Rigid, smooth walled pipe is all we allow on our projects. PVC/ABS or sheetmetal. If you are in a cold climate it will need to be insulated too. Do not use cheapo plastic accordian dryer ducting. Even the metal accordian isn't very good.

Antss, I'm not doubting your advice, but when I bought our two Fantech fans last year, their instructions specifically call for flexible duct. In bold face text, they say: "Fantech recommends insulated flexible duct for all bathroom exhaust applications." I don't know why they recommend flex over rigid ducting, but I'm just sharing this info for anyone who's considering buying a Fantech fan.

-- Eric

Here is a link that might be useful: Fantech installation manual (PDF)

Fantech is just covering their bases and providing a good service at the same time.

They want the ducts insulated for the condensation issues and insulated flex duct is smooth (relatively) on the inside so that takes care of the static pressure loss associated with the corrugated types. Their fans' design don't necessitate use of flex insulated duct, it's simply a good choice from a cost / performance / ease of install perspective.

Rigid smooth wall pipe is more durable and has less static pressure loss than flex duct, but is sometimes more difficult to install ESPECIALLY if it is insulated properly after the fact by hand.

We often use a hybrid arrangement with Fantech and other remote blowers - ins/flex duct from the grille to the motor and then rigid duct to the outside. The flex has install advantages in the confined spaces often left in shower stall ceilings. The spaces we run the ducting in are almost always conditioned so the ducting itself being insulated is not really an issue. This is not the case in attics or crawlspaces that are not insulated or conditioned - so proper design a detailing for each project is necessary.