Venting for bathroom w/Steam shower

15 years ago

I am doing a steam/shower (5x6) and the other portion of the bathroom is 11X8. I'm looking at a fantech (2 line) inline solution but am not sure how to prevent steam from escaping while steaming. I know there's a damper but that will only prevent backdrafting. There's also an Iris but that seems to be installed in the attic and not a finished piece that would attach to the grille.

I'm also wondering on what size unit i need. I've researched and seems there's multiple ways to calculate CFM's. Based on my dimensions, my range seems to be b/w 63-100 CFMs. Also, should I increase since I see .4 static pressure being the number that i would need?

Thanks in advance and I appreciate any information you can give me. Seems my electricial guy is behind the curve on this and I'd like to prevent any mishaps before I start.

Featured Answer

heimert

15 years ago

We had a steam shower installed and there's no fan in it. It's steam-tight, so during the shower the steam stays in. When done, we use the bath fan outside the shower and leave the door open for the shower to dry out. No problems so far.

In other words, I'm not sure you need a fan inside the shower unit.

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Comments (6)

MongoCT
15 years ago
Tim,

Having a vent in the shower is prohibited in many areas. Some areas that do allow them require that the vent opening have a sealable damper/cover at the opening itself.

The idea is that no steam is allowed to go into the duct while the steam unit is running. Hot steam in a cool duct means lots of condensation in the ducting within your walls.

And then there are areas that have no restrictions at all.

Personally, I would not put a vent in a steam shower.

I'd recommend the steam shower be built with Kerdi over cement backer board, with the Kerdi on all six sides of the cube.

For the door, the better ones are either almost floor-to-ceiling doors, or they have a functioning transom over the door. The reference to "better performing" is for post-steaming ventilation. A transom or tall door allows better air movement, ventilation and drying.

With no vent in the steam shower, have your fan opening on the ceiling just outside the door/transom.

You take your steam, then when you're done turn the shower water to full cold. The blast of cold water will quickly condense the steam out of the air and leave just a bit of residual humid air. Then open the door and/or transom and turn on the fan to ventilate any residual moisture as usual.

I'll try for more later, time to go swimming with the kids.

Mongo
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tim022
Original Author
15 years ago
Thanks heimert - I've read many posts here regarding venting in a steam where some do and some don't vent. Is your fan ceiling mounted or inline? Have you had any issues with the motor if ceiling mounted with the steam hitting it? Or is the amount of steam that would enter the room nomimal? I'm trying to avoid prolonged moisture (ie mold), and would think the venting would be a cure but maybe it's overkill...
tim022
Original Author
15 years ago
Mongo - Thanks. Is an inline fan then overkill since i'm breaking down the moisture to that of a shower? Also, I'm not sure how many CFMs i should be looking for in a fan.
I've read the Pan whisper.. and fan tech are good. Any thoughts? I'm looking for venting only no heat/light, etc.
PS
Kerdi it is, tray and all...viewed your shower montage many times.
MongoCT
15 years ago
The two you mentioned are both excellent. The Panny whispers can be a bit noisy if the ducting has too many bends, but it;s a good unit.

Fantech's stuff is excellent. If you want quiet, the fantech is the winner. And I think it's a better fan.

The other plus is it's easier to work on a fantech that is up in the attic than trying to do whatever with a tiled-in ceiling mounted fan.

With the size of your shower and the size of the bath outside the shower, I'd do a fantech with two lines, one outside the steam room door, the other elsewhere in the bathroom.

You have a 30sqft in the shower and 88sqft of bathroom outside of the shower, total 118. I'd add another 50 for the "steam" part of the shower, so about 168 cfm figuring it one way.

For baths over 100 sqft, which your's is, you can calculate using a certain cfm per fixture; 50 for the toilet, 50 for a tub, 50 for a shower. Add another 50 if you have a steam shower and/or a whirlpool. Going this way you get 150 if you don't have a tub, 200 if you do.

So either way you want 150-200 cfm at .4 static.

The following numbers might be incorrect, this is off the top of my head...but the Fantech two-grill PB-230-2 at .4 is right around 195cfm. the single grill Pb-190 is about 160cfm at .4 static.

If you want two grills, both outside the shower, do the PB-230. That's what I'd do were this my bathroom.

If you just want one grill outside the shower, do the PB-190.

If you want a fan inside the steam shower, then I'd recommend two separate fans on two separate timed switches. One inside the shower, one outside. Both could be PB-100's. those are each around 80cfm at .4 static.

I highly recommend you get a timer switch for the fan. The switch keeps the fan running for 'X' minutes after you turn the switch off.

Mongo
tim022
Original Author
15 years ago
Hi Mongo, Thanks again. I'll go with the 2 line both outside PB-230 and use the 30 minute timer.