I have read that a bathroom exhaust fan should replace the room air 6 to 8 times per hour.
To be on the safe side, I calculated for my bathroom:
3.5 x 3 x 2.5 = 26.25 cubic meters (m³) = 25m³ x 8 = 200m³ fan capacity.
Now... a fan with that capacity doesn’t seem to be very common. At least, most are apparently smaller.
Also, showering typically takes about 10 to 20 minutes, maybe a bit more, and bathing about 30 minutes.
Do I really need a 200m³ fan then? Probably not?
The larger fans I’ve found have a capacity of 150m³. Wouldn’t that be enough?
I’m not sure if I’m overthinking this... I have an exposed roof truss that should remain untreated, so I don’t want to take any risks there. But maybe that’s an advantage because the wood can absorb some moisture and slowly release it again?
How well do these humidity sensors actually work? I would probably set mine to 60 or 65% to prevent mold and damp spots on the wall and wood.
I would rather avoid connecting the fan to the light switch. It’s better to have a separate switch that starts the overrun timer or keeps the fan running until you switch it off manually.
Basically, I would fully rely on the sensor anyway, since that’s the most convenient option.
What kind of fans do you have in your bathrooms? I’m surely not the only one with a 10m² (107.6 sq ft) floor area and about 2.5m (8.2 ft) ceiling height.
Edit: Many fans also only have an overrun time of about 20 minutes. That would mean a 150m³ fan exchanges 50m³ of air in 20 minutes, which is just twice the room volume—far from 6 or even 8 times air exchange.
So somehow none of this seems to add up...
If the fan runs for 20 minutes and is supposed to exchange 8 times the air during that time (while the remaining 40 minutes of the hour have “no” exchange), then I would actually need a 750m³ fan...
Off the top of my head, I don’t think even a kitchen range hood exhaust has that capacity.
To be on the safe side, I calculated for my bathroom:
3.5 x 3 x 2.5 = 26.25 cubic meters (m³) = 25m³ x 8 = 200m³ fan capacity.
Now... a fan with that capacity doesn’t seem to be very common. At least, most are apparently smaller.
Also, showering typically takes about 10 to 20 minutes, maybe a bit more, and bathing about 30 minutes.
Do I really need a 200m³ fan then? Probably not?
The larger fans I’ve found have a capacity of 150m³. Wouldn’t that be enough?
I’m not sure if I’m overthinking this... I have an exposed roof truss that should remain untreated, so I don’t want to take any risks there. But maybe that’s an advantage because the wood can absorb some moisture and slowly release it again?
How well do these humidity sensors actually work? I would probably set mine to 60 or 65% to prevent mold and damp spots on the wall and wood.
I would rather avoid connecting the fan to the light switch. It’s better to have a separate switch that starts the overrun timer or keeps the fan running until you switch it off manually.
Basically, I would fully rely on the sensor anyway, since that’s the most convenient option.
What kind of fans do you have in your bathrooms? I’m surely not the only one with a 10m² (107.6 sq ft) floor area and about 2.5m (8.2 ft) ceiling height.
Edit: Many fans also only have an overrun time of about 20 minutes. That would mean a 150m³ fan exchanges 50m³ of air in 20 minutes, which is just twice the room volume—far from 6 or even 8 times air exchange.
So somehow none of this seems to add up...
If the fan runs for 20 minutes and is supposed to exchange 8 times the air during that time (while the remaining 40 minutes of the hour have “no” exchange), then I would actually need a 750m³ fan...
Off the top of my head, I don’t think even a kitchen range hood exhaust has that capacity.
S
Sebastian7930 Jun 2016 18:18That really doesn’t make any sense either...
B
Bieber081530 Jun 2016 19:40garfunkel schrieb:
I have read that a bathroom exhaust fan should replace the room air 6–8 times per hour. That is commonly stated, although I couldn’t quickly find a reliable primary source. Two thoughts come to mind:
- This should definitely be considered along with short operating times for the fans (around 15 minutes...), so the actual volume of air moved (in m³) is not that high.
- With the high airflow rates involved (in m³/h), it is important—not only in new builds—to consider the supply air. Looking only at the bathroom fan is not enough.
Is this for a new build or an existing building?
G
garfunkel30 Jun 2016 20:10I am renovating an old building myself with a complete refurbishment. Among other things, I have some concerns about the untreated wood of the exposed roof structure in the bathroom.
…I installed a 100mm (4 inches) fan, controlled by a separate switch, because I don’t want to lose the radio in the early morning while brushing my teeth.
That was a good decision!
When we take a bath, the fan isn’t really necessary. However, when showering—even with a handheld showerhead—I feel like I would need a 600mm (24 inches) fan. Everything fogs up immediately. That’s the downside of an open shower…
If you have an enclosed shower, it’s much better (we had this before).
Possibly install the fan directly above the shower! And for unpleasant bathroom odors, install a toilet with an exhaust air recirculation system (works perfectly!!!).
Hope this helps
https://www.hausbau-forum.de/threads/zeigt-her-eure-baeder.12054/page-3
That was a good decision!
When we take a bath, the fan isn’t really necessary. However, when showering—even with a handheld showerhead—I feel like I would need a 600mm (24 inches) fan. Everything fogs up immediately. That’s the downside of an open shower…
If you have an enclosed shower, it’s much better (we had this before).
Possibly install the fan directly above the shower! And for unpleasant bathroom odors, install a toilet with an exhaust air recirculation system (works perfectly!!!).
Hope this helps
https://www.hausbau-forum.de/threads/zeigt-her-eure-baeder.12054/page-3
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