Ventilation for a shower room with five showers

[luc]

Hello everyone,

We have a shower room that has five showers. Presently, each shower has its exhaust grille hookup to the same extraction fan in the attic. We are having some condensation problems with this extraction fan in the attic because of the cold climate. Anyone know of a better way to extract the air?

Kind regards,
Luc

[luc]

Anyone know if we could use an ERV/HRV to ventilate? We could have an exhaust grille next to each shower? Using an ERV or HRV would not create a negative pressure like an exhaust fan.

Kind regards,
Luc

[gator37]

Not sure I understand the total question but you want to have the shower area under a negative pressure. Does your exhaust fan, exhaust to the outside?
Where is the condensate forming?

[Dana]

The little Panasonic single-room ERV probably isn't going to cut it in a 5- shower situation, but a bigger HRV (not ERV) might. An HRV would still have condensate-disposal & defrost cycles to contend with during severe weather, but those features are already built in. You'd need at least 500cfm (100cfm per shower), which could be operated under dehumiditsat control in winter, stopping when it gets down to ~30-35% relative humidity.

Whether HRV or exhaust-only, sealing and insulating the exhuast ducting is critical. In very-cold areas you may need to devise a system for condensing and condensate disposal to keep frost from clogging up the vent where it exits the building too (a bigger issue with an exhaust-only system than with an HRV.)

[luc]

Thanks gator37 and Dana for replying. I appreciate it.

The condensation problem is in the attic because it is quite difficult to insulate the ducts and the exhaut fan properly. Presently, the exhaust from the exhaust fan runs in the attic and terminates in the soffits which creates another problem when the MAXIMUM on the roof pulls the humidity back in the attic in the winter. We then get frost in the attic under the roof around the exhaust fan. We want to redo the ventilation with all the ducts and HRV or exhaust fan inside the building to prevent the condensation and frost accumulation.

You'd need at least 500cfm (100cfm per shower), which could be operated under dehumiditsat control in winter, stopping when it gets down to ~30-35% relative humidity.

Why so much? The shower stalls are small (30'' x 63'' x 95'') and there are only 15 persons using them(a maximum of 15 showers per day). If the HRV runs all the time could I decrease the CFM by shower? I did some research and the NOVOCLIMAT program here in Québec recommends 30 to 75 CFM for each bathroom.

Kind regards,
Luc

[gator37]

luc
I am unfamiliar with the mechanical code requirements (shower/locker room, etc. exhaust) in your area but you might want to check the exhaust requirements just to make sure.
Definitely need to exhaust in a location where the air exhausted does not get back into the attic.
If you are renovating the system including rerouting the duct you could use individual ceiling exhaust fans or just stay with one exhaust fan design similar to what you have now. Dependant on your layout, you probably could satisfy the exhaust requirement with one single exhaust grill in the shower room ducted to an inline fan and exhausted to an outside wall exhaust cap or louver with a weighted back draft damper. I would still insulate the ducts if they are concealed .
Does the shower area have any adjacent areas you can get makeup air from or is it a stand alone building?
In reference to the Novoclimat system I am not a heat reclaim systems in our area, but that is me. (more parts more maintenance) If your shower facility is stand alone I can understand why you want to consider the Novoclimat system.

Dave

[luc]

Thanks Dave for the reply.

Does the shower area have any adjacent areas you can get makeup air from or is it a stand alone building?

There are 15 bedrooms on the same floor as the shower area. I do want to reduce the negative pressure in the building because each bedroom has its own toilet room with an exhaust fan. This is why I am looking for an HRV.

NOVOCLIMAT is a contruction program for superinsulated air tight houses. The houses have to be under 2.5 air change per hour during a blower door test of 50 pascals. Even thought our building was not constructed with the NOVOCLIMAT standards, they give some good ideas.

Thanks,
Luc