Ventilation in bathroom

Mike T., Swampeast MO

Large bath with large steam shower (sealed save the inevitable leaks around the lights and numerous control valves). Large corner Jacuzzi tub.

Old house but little natural infiltration in this space as the glass is all glass block in this room.

Only current given regarding ventilation is the exhaust fan (properly sized) and vented directly through rigid metal to the outdoors.

Big mechanical closet with an outside wall adjoins the shower.

Am concerned about humidity buildup--particularly above the shower.

Because of the way I have configured things, nearly anything in the way of ventilation is currently possible BUT I'll be finishing the mechanical closet next month and many of the options will end.

Suggestions please... Anything at all...

This was my first steam shower and I followed mfgr. suggestions to the letter. I had wanted to incorporated a ventilation system in the shower proper but did not do so because ALL steam generator mfgrs. advised against this.

Because the door fully seals, it must be left open to allow the shower to dry. If you ever design one of these I HIGHLY suggest that you incorporate some form of transom--either integrated into the main door or separate!

AKO

ventilation

Short of actively dehumidifying the space, your best chance of controlling moisture is to properly ventilate the space. You say you have an exhaust fan, which is good -- it should be sized to give you approximately 8 air changes per hour. It is best to locate the exhaust grille as close as is practical to your steam shower, and if you need to duct it out, make sure the ductwork is insulated, sealed and pitched toward the outlet from the house.

Since you don't have a good make-up air source, you may want to consider installing an energy recovery ventilator that brings in outdoor air to replace what is being exhausted in the bathroom. This usually isn't necessary, but as you point out, it depends on the construction and whether you have enough infiltration to compensate. If you're in a heating climate, you'll have to add some heat, too.

On the other hand, if you've got sufficient make-up air in the house, outside of the bathroom, you could install a transfer air duct -- a ceiling grille in a corridor ducted to a ceiling grille in the bathroom.

AKO

ventilation

Short of actively dehumidifying the space, your best chance of controlling moisture is to properly ventilate the space. You say you have an exhaust fan, which is good -- it should be sized to give you approximately 8 air changes per hour. It is best to locate the exhaust grille as close as is practical to your steam shower, and if you need to duct it out, make sure the ductwork is insulated, sealed and pitched toward the outlet from the house.

Since you don't have a good make-up air source, you may want to consider installing an energy recovery ventilator that brings in outdoor air to replace what is being exhausted in the bathroom. This usually isn't necessary, but as you point out, it depends on the construction and whether you have enough infiltration to compensate. If you're in a heating climate, you'll have to add some heat, too.

If you've got sufficient make-up air in the rest of the house through infiltration, you could install a transfer air duct -- a ceiling grille in a corridor ducted to a ceiling grille in the bathroom.

Mike T., Swampeast MO

Climate is officially described as "continental"--what I believe to be a euphemism for, "Who knows what!" The most constant thing is high humidity year-round.

A dedicated dehumidifier is a possibility but I'd like to try to avoid the expense of running another (big one in the basement), the noise and the maintenance.

It does though sound as if you believe a dedicated dehumidifier would be the "best". Correct?

Exhaust fan is properly sized and very well sealed but I did not insulate the duct--it is only about 3' in length. In a "worst case" test where I ran the steam on a muggy afternoon and "fanned" the steam out of the shower with the door, ½ ounce or so of water dripped out of the fan onto the floor.

There is a forced A/C system but no return in the bath--I wanted one but gave in to an argument regarding the toilet.

I can get makeup air from MANY sources. I know air is lazy and really hard to predict actual flow, but I can fairly well achieve "sealed" makeup air from:

1) The top of an open stairwell. Hot water radiator below but no dedicated A/C ductwork.

2) Eave space. 1903 home. I can only describe the eaves as being constructed by a true master carpenter. They have what I would call "just right" infiltration after 100 years. Found his signature board in the renovation--he dotted his 'i's with little hearts like a gradeschool girl writing you a note...

3) Conditioned attic space.

4) An adjacent room (same A/C system with oversized return for the bath) by slightly dropping the ceiling in the stairwell.

Will include the power/drainage for a dehumidifier regardless as must have leak protection for the steam generator anyway...

From which "source" would you suggest the makeup air?

Jack Smith

make-up air direct from outside

heretic

Humidity controls

Not exactly an answer to your makeup air question, but these might help:

Tamarack Technologies makes these cool humidity controls for exhaust fans. The most interesting one is the "D" model, which operates based upon the differential between a sensor in the bathroom, and another sensor in a 'benchmark' location.

http://www.tamtech.com/humitrak.htm

Mike T., Swampeast MO

Thank you sir!

That's the kind of control scheme I had thought about but could not find previously. Figured that making my own would be problematic and terribly expensive as the humidity sensing devices I found were either inaccurate and unreliable or hideously expensive.

Will try to research the actual device they use, but their statements sound good at least.

Thanks again!!!!

Mike T., Swampeast MO

Direct from the great outdoors is really what I wanted...but only in SOME circumstance and variable with conditions. Such would only ADD to the problem in the all-too-common situation around here where the outdoor dewpoint hovers around the indoor temperature.

Granted I like to make "gizmos" but such would be exceedingly complex.

See post below and look at the link. REALLY nice product (from their literature at least).