Do I need another bathroom exhaust fan?

[PatDIY_Dad]

Hi

We have a double shower with 2 shower heads. Wife and kids love staying in there too long with the water really hot to create a sauna effect

We had just a regular exhast fan that only pulled about 300m3/hr of air ( those standard ones that builders supply)

The bathroom would have water running down the walls. This can create mould so I took out the fan and installed this:

https://www.bunnings.com.au/deta-250mm-high-capacity-exhaust-fan_p4441224

I think its better but I still see wet walls on the high spots of the walls. Which means also the ceiling is probably also wet

( check video link cant upload videos https://photos.app.goo.gl/SJ7UxjvoDzNecjkdA )

Two questions

1. Would I just need to install another fan thats closest where the most steam is settling?

2. Our exhaust fans are just vented to the roof cavity. Would it be better to vent out into the roof? If so what do I need in order do this? If I install a 2nd fan can I join 2 ducts into one larger one to just install 1 roof cowl? or would 2 roof cowls be needed ? ( more work )

Thanks !

[Jason]

Hi @PatDIY_Dad,

When they shower, do your family members have the door open (at least a little) or a window open? Extraction fans remove moist or stale air from the bathroom, but for them to do so efficiently, fresh air needs to replace the air being extracted. Without an intake source, the fan struggles to create airflow, reducing its effectiveness. Adding another fan might not solve your problem...

I look forward to seeing input from other community members.

Jason

[PatDIY_Dad]

They usually have the door closed as its winter but the bathroom should have plenty of ventilation even without the window opened becase its the ensuite and has no door. You get to the ensuite from the master bedroom to the walk in robe 

Here is a floor plan of it so you know what I mean. But we can try open the window a little. Mrs will complain though as she likes the whole bathroom like a sauna without cold air lol

[PatDIY_Dad]

I bought this fan trying to resolve the issue I posted here:

https://www.workshop.bunnings.com.au/t5/Bathroom-and-Laundry/Do-I-need-another-bathroom-exhaust-fan/...

But eventually I want to duct the steam outside. Can these types of fans be ducted to the outside or is this not suitable? 

When I google it I only see fans that have special duct port on the side of it

[JacobZ]

Hi @PatDIY_Dad,

Unfortunately, I don't think you are ever going to completely get rid of the condensation, especially in winter.

The problem is that the tiles are going to be cold. When you introduce warm air and moisture in the form of steam, it will hit the cold tiles and condense. 

If the walls were well insulated to keep the outside temperature outside, and the inside temperature of the bathroom is kept at a higher temperature so the tiles are not below the dew point, then the steam would not be able to condense on the tiles. At this point in time, it is probably not possible to do this without a full bathroom reno. 

You could use a heater to, in a sense, "preheat" the room, so that the surface of the tiles is not so cold. This might help to reduce some of the condensation.  

A higher capacity fan, such as the DETA 250mm High Capacity Exhaust Fan, would certainly help to move that hot air on before it can condense on the cold tiles. Keeping windows ajar and allowing for better air flow will also help, but unfortunately, I think some condensation is inevitable.

If you are looking to duct to the outside of your property, you would be better off installing a DETA 250mm Side Duct Exhaust Fan. The capacity would be reduced, but you could always add a second one if necessary.

You could check out @CSParnell's post about Changing an open air exhaust fan to a ducted exhaust fan for some guidance.

Also, allow me to tag our experienced members @MikeTNZ, @Nailbag and @Dave-1 for their thoughts. 

Let me know if you have any further questions.

Jacob

[Dave-1]

Good Afternoon @PatDIY_Dad 

Mmmm thinking along the post.

I would actually install a second fan to start with, I would also monitor the ceiling space but really would expect the area to be fine with the exaust into that space.

The problem is your wife and kids like that sauna effect, exhausing the steam/heat then means they will crank up the water more so to still have that same effect lol A never ending catch up and then fix and then starting again.

I have seen enclosed shower areas somewhere that would hold all the heat and steam in tho not sure about mould long term.

I like the idea of preheating the room, even with the toasty heat lamps as you shower. It will lower the need to create the sauna effect

If the heat from the lamps keeps the air warm, the air may manage to hold the moisture in the air as its exhausted instead of touching the tiles and chilling to water drops.

Dave

[Nailbag]

Hi @PatDIY_Dad 

As @JacobZ suggested, preheating the room can make a huge difference in moisture build up as can a high-volume fan ducted to the outside not the internal roof space. 

The position of the fan is also very important. They should be as close to the shower head as possible being the source of steam from the hot water. Often fans are placed away for cosmetics, but then are not working efficiently. 

A few weeks back I had to resolve a mould issue in a bathroom. The main cause was no heating, fixed windows and the exhaust fan at the opposite end of the long walk in shower. 

Nailbag

[PatDIY_Dad]

Thanks for the advice @JacobZ 

I just actually bought https://www.bunnings.com.au/deta-250mm-high-capacity-exhaust-fan_p4441224 and it works but still get some steam build up on the far left of the room andf I beleive its just because the fan location is not close enough to the 2nd shower head. ( check my edited floor plan )The ensuite where the shower is gets cold during winter as its next to the gargage with no heating and insulation + the front of the ensuite is facing the front of the house

I think id try install a 2nd fan but worried also about steam going into the roof. We do keep nearby stuff stored up there to but is about 2-3 meteres away from the exhaust fan. But still can mould be an issue in the long run with 2 shower heads?

We've been living in the house since 2020 and if I have a look and dont see signs of damage from the steam should I bother going a ducted fan? or not worry about it?

If so I would go 2 x https://www.bunnings.com.au/deta-250mm-side-duct-exhaust-fan_p4441225 but they arent as powerful

[JacobZ]

Hi @PatDIY_Dad,

Mould could always be an issue when you are pumping moist air into the roof cavity for it to condense. It would be worthwhile using the ducted vents, as you could ensure that moist air is being ducted outside, where it won't cause issues.

Two ducted vents, with one relatively close to the shower and the other one closer to the sinks, would be what I'd do.

The duct connection port on the DETA 250mm Side Duct Exhaust Fan is 150mm, so you would need a Builders Edge 150mm x 3m Flexible Duct, Builders Edge 150mm White Grill Vent with Insect Screen and some zipties and insulated duct tape like this Ametalin 48mm x 50m Reinforced Insulation Ducting Tape to connect the duct to the connection ports and seal them.

Let me know if you have any further questions.

Jacob

[PatDIY_Dad]

Thanks all for the help

Ill start off by installing another fan near the 2nd shower head towards the left side of the room and will duct it outside

WHat is better ducting to the roof or eave?

I think ducting to the eave is better but you will see a grill