# Forum Home Renovation Bathrooms  Exhaust fan in bathroom

## tcf

Hi all, 
I need to put an exhaust fan in a bathroom. Only problem it is a lean-to (skillion) roof with only approx 100mm clearance or roof space to fut the fan box into. Most fans are at least 150mm main box size. The shower is at the lower end of the skillion roof and as such the hot air will be going across the room to the highest point about 2.5m away. 
low>>>>>>>>>>>high 
__________________   
|_X_______________| 
the above diagram is where the shower (X) is located in relation to the room and the roof line. The roof slopes upward from the low to high end. Where would the best place be for an exhaust fan? It would be in the middle to the high end, but I am limited by roof space and the wall height is only 2m at the low end so cant put in wall above shower as it isnt high enough. 
All suggestions/comments welcome and appreciated.

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## murray44

You've really got to just put it where it will fit. It will still work way better than nothing. My old in-laws had similar to you but a much steeper roof i.e. 2.4 at the low end and probably about 3.5 at the high end. They had the fan in the window at the low end and that worked adequately, just a little lingering steam at the high end. 
By the way, I'm glad you told us that the roof slopes upward from the low end to the high end.  :Biggrin:

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## juan

My thoughts are that you may need some sort of fabricated metal box flashed on top of the roof to accommodate the fan and provide a clear exhaust path to the outside of the bathroom. This would then allow you to have something flash like an IXL Tastic.
Am I missunderstanding that you are thinking of blowing the exhaust air into a 100mm cavity between the ceiling and the roof.  Methinks this will not provide the important air exhaust that is required to keep a bathroom moisture level under control. It could also lead to problems with moisture in the roof cavity. I will cost extra money but should solve the problem properly.

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## tcf

Murray, reading back the 'upward' comment is quite good haha 
Juan, I am not wanting to vent into the 100mm roof cavity, rather just try and best place the exhaust fan box in the cavity and vent to the outside. A plumner mate of mine seems to also think that flashing the roof to accomodate the exhaust fan dimensions is the best idea.

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## lbg

if you're making a hole and putting flashing in it shouldn't matter where you install... I'd go for somewhere at the high side. heat rises, steam is hot.....

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## juan

Sorry got the wrong handle.  No expert on fans but our IXL is about 1000mm from the centre of the shower cubicle in a flat ceiling bathroom. It is fantastic. The amount of air it pulls out is limited by the space under the door that permits air into the room. Open the door and the air flow increases dramatically. Obviously you will not put it directly above the shower but I would put it as near to the shower cubicle as possible so that most of the exhausted air is that which is most heavily laden with moisture.

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## gastric me

just to put in a wall exhaust fan instead, and stop dicking around with trying trying to put it in the roof

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## intertd6

There are ceiling mounted 4 in 1s with side vented fans which can go in the roof cavity
I have one in a similar bathroom with 125mm rafters. With 100mm rafters you would just have to pack out the plaster face with 25mm or so material & mount to that.
regards inter

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## tcf

intertd6, 
that sound like a good and small option, but with almost zero roof space and no eaves to vent to its still an issue. I guess i could still vent the side exhaust out the top of the roof with some sort of flashing.

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## Fiona

Hi Tcf, 
I have exactly the same problem as you and was wondering if you resolved the problem and could let me know the outcome?? 
Juan, 
Why can't you put the fan directly above the shower?? As my shower is on the low side of the ceiling there is little room between the screen and the ceiling, therefore, it seems as though steam is getting trapped. The paint is peeling above the shower as a consequence. 
Gastric me, 
I can't put a fan in the wall because I have tiles to the ceiling, a louvre window to one side of the shower and the other wall leads to my front entrance and I do not want a fan obstructing this area for aesthetic reasons.  
Any advice from anyone would be greatly appreciated. Tcf, if you have solved the problem, I would love to see the result!!! 
Fiona  :Smilie:

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## GeoffW1

> just to put in a wall exhaust fan instead, and stop dicking around with trying trying to put it in the roof

  Hi, 
That would be a lot of dicking around, wouldn't wouldn't it?  :Rofl:  :Rofl:  :Rofl:

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## Moondog55

Not a technical answer but I have always wondered why people insist on sucking all those nasty wet bathroom and kitchen fumes into the roof space??
Vent thru the wall and get the steam and smells outside as quickly as possible

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## GraemeCook

Good Morning TCF 
My bathroom is also skillion, albeit with 9+ feet sloping ceiling.   When I put in a IXL Tastic I built a chipboard box for it, partly to lower the fan/heater, partly because of the sloping ceiling and partly because of the very limited roof cavity.   
Also, its not a good idea to vent moist air into the roof space, so I put a vent directly above the Tastic - used an old wok as a rain shield, probably overdid the vent diameter! 
Cheers 
Graeme

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## noeyedeer

Hi tcf,
I just posted a reply to a similar question so here goes a cut n paste - 
"I fitted an exhaust fan to our ensuite ceiling, there is no roof void as the ensuite was built onto what used to be a verandah, so just 4 inches to the corrugated roof. I cut the top off a plastic bucket to make a ducting piece and fitted the whirly-bird directly over it - the main reason for the "ducting" was to keep dust from the roof area from entering the bathroom through the fan. 
Turn on the fan and the whirly-bird goes flat chat, its great. Also it spins without the fan on giving the ensuite a good ventilate all day and night, no mould at all, its been a couple of years since it was done and no problems." 
Hope it might help some others even if its too late for you.

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## Lucky Legs

Ceiling vent fan to the roof seems like your only option along with boxed dropping the extractor a little from the ceiling plane (from your discussion/comments) but bear in mind its all very good to get fresh air ventilation from outside (in summer) - via a covered whirly bird etc - but when your fan extractor is off (not pusing air to outside) when it very cold (in winter) you will get cold draughts entering probably making your bathroom the coldest room in the house!  The solution is to look for extractor fans that have a ***backdraught flanges***, so that only moist air can be pushed out and cold outside draughts can't come in.  The greater the capacity of your fan the less likely mold will occur anyhow (summer or winter) - you can get industrial/commercial extractor fans too...So the summer benefits of fresh air draughts might be good then (e.g. to further reduce mositure molds for low powered or poorly placed fans that don't do the job alone), but think about winter draughts and the beenfits of an optimal powerful extractor for your area space.  Over-engineering is better than under-engineering, and warm draughts are better than cold (freezing) ones!

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