Browse Forums Bathrooms and Laundry 1 Sep 06, 2012 11:01 pm Hi all, I'm getting a lot of condensation in the bathroom when we shower with the exhaust fan on. The fan in the bathroom is located near the shower and it's ducted to the outside as we have a metal roof with sarking. After we shower the walls are wet and water drops appear on the ceiling. The fan is sucking as we can feel a draft under the the door when the fan is on. The internal walls are insulated. We have floor to ceiling tiles. The shower rose is large, makes it feel like you're standing in the rain. The duct and roof cowl are ok and not blocked, I checked them. Even our builder is stumped. Ive been talking to him trying to work it out and find a solution. The company that supplied the fan said the fan is oversize for the room dimensions and they can't explain the condensation. Its the most powerful ducted bathoom exhaust fan they sell, but I've noticed that these still don't move as much air as a standard fan that cannot be ducted ie they exhaust ino the roof space. Now we are thinking of just putting in a standard fan with more suction but letting it exhaust into the roof space as these fans cannot be ducted. Anyone else had this problem? Any thoughts? My concern is putting in a new fan and exhausting into the roof space and getting condensation/ventilation issues in the roof space. I'm hoping someone can help please so if you know the problem and solution then please respond. Cheers Horaldo Re: Condensation in bathroom during shower 2Sep 07, 2012 8:34 pm I'm hoping to learn from this thread cos we're looking at doing some bathroom improvements. But here's some thoughts of mine. As I understand it it's desirable to duct to the outside if you've got a tiled roof and it's necessary to duct to the outside if you've got sisalation or colourbond, so I think your idea of doing away with the ducting is a no go though I know what you mean, our first house simply exhausted into the ceiling and it worked so good! Does the fan have a draft flap and is it installed properly and moving freely and is the vent pipe the correct diameter and attached correctly? We had some issues like that and when they were fixed the air movement noticeably improved, but we still get some condensation sometimes. Which brings me to the other factor of temperature and things like dew point, which I'm hoping somebody else will explain better than I can. We heat up the room first in cold weather and don't open the window cos I've heard the colder air can make things worse. I'd love to hear any more ideas about what can be done. Re: Condensation in bathroom during shower 3Sep 07, 2012 9:11 pm Hello horaldo. . . I'm wondering. . . if you can feel the air being sucked under the door, maybe you have a bit of a vacuum/airlock going on, where the fan is working as hard as it can, but the air intake into the room isn't enough for the fan to suck air from the room. Maybe you could try opening the door a little bit when you shower? If you try this, let us know how you go. Re: Condensation in bathroom during shower 5Sep 07, 2012 9:44 pm We have same problem except we have the exhaust fan And a heater/light/exhaust aswell. I know the exhaust on these arent the best but with both i thought would be perfect...and they come on together. But still so much condensation. Re: Condensation in bathroom during shower 6Sep 08, 2012 7:13 am Hi jazzjezs I'm wondering if the roof cowl that the duct is connected to is sufficient ventilation for the roof space if it acts as a passive vent when no ducting is connected to it. There's quite a draft in there when I was up in the roof space the other day, so the roof space is not as sealed as I would have thought and leads me to believe any moisture would just get blown out. We also have a panel heater in the bathroom with a timer so the room is nice and warm. Without it on, the condensation is worse still. Jodge, there's a 10mm gap as per the fan manufactuetes specs. I'll try opening the door. Little and see what happens and report back. My gut feel is a larger fan is definitely needed. These ducted models just don't suck enough I reckon. The hole/opening/intake to these ducted fans is like 3-4 inches wide and even though the ducting is wider, I reckon the fan opening creates a bottle neck. The standard fans with those big blades have a full 250+mm opening so air would flow more freely. The current fan has a hell of a lot of condensation at the fan intake suggesting it can't cope with the steam in the room maybe? I don't know, all I know is those old style fans that were not ducted simply worked. Cheers Horaldo. Condensation in bathroom during shower 7Sep 08, 2012 8:37 am We have the same issue. We've started heating the room before showers and it has reduced the problem though not stopped it. We were/ are getting mold build up on the ceiling near the shower and this has slowed considerably now we are heating the room. Wasn't an issue in summer just winter. And other cooler months. Re: Condensation in bathroom during shower 13Sep 09, 2012 1:11 pm Quote: I'm getting a lot of condensation in the bathroom when we shower with the exhaust fan on. The fan in the bathroom is located near the shower and it's ducted to the outside as we have a metal roof with sarking. After we shower the walls are wet and water drops appear on the ceiling. The fan is sucking as we can feel a draft under the the door when the fan is on. The internal walls are insulated. You don't say whether the ceiling space is insulated. You say that there is a metal roof with sarking underneath but this alone is not enough. You should have a decent foil backed blanket under the metal roof sheeting then an air gap then 90mm batts on top of the plasterboard ceiling. I'd say that is where your main problem is. Condensation is forming because the hot air inside is hitting a cold surface ( walls and ceiling ) without adequate insulation to negate this. Below is what you should have although I would have used a 50mm foil backed blanket rather than ordinary old sarking. Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Quote: Now we are thinking of just putting in a standard fan with more suction but letting it exhaust into the roof space as these fans cannot be ducted. Anyone else had this problem? Any thoughts? My concern is putting in a new fan and exhausting into the roof space and getting condensation/ventilation issues in the roof space. I would not do this as all you are doing is setting yourself up for more problems. All fans/vents etc should be vented to the outside either vertically through the roof or horizontally through the walls and not into a ceiling/roof space or wall cavity. Stewie Re: Condensation in bathroom during shower 14Sep 09, 2012 2:40 pm can you put a shower dome on or is it the wrong shape? http://www.showerdome.co.nz/ (ugly, but will cut out all the water) Re: Condensation in bathroom during shower 15Sep 09, 2012 4:11 pm There are batts ontop of the plaster ceiling, then sarking under the metal roof. There is no foil backed blanket under the metal roof sheets. All walls (internal and external) are insulated with batts. PHL thanks for the link. Looks like this company have the standard 250-300mm opening fans that can be ducted so I'll be looking into this option. Re: Condensation in bathroom during shower 16Sep 11, 2012 11:42 am For horaldo, jazzyjess and others that want a bit more info, here is a booklet on Condensation in buildings put out by the Australian Institute of Architects http://www.google.com.au/url?q=http://w ... 71aRWaIfyw A lot of info and more than you really need but some very pertinent articles on insulation and dewpoint. Here is another article aimed more at the layperson but still informative. http://www.google.com.au/url?q=http://w ... ndDharJyrw I would also suggest horaldo, if not using the foil backed blanket then at least a perforated sarking under the roof. Stewie Re: Condensation in bathroom during shower 17Nov 12, 2012 9:58 pm Stewie D For horaldo, jazzyjess and others that want a bit more info, here is a booklet on Condensation in buildings put out by the Australian Institute of Architects http://www.google.com.au/url?q=http://w ... 71aRWaIfyw A lot of info and more than you really need but some very pertinent articles on insulation and dewpoint. Here is another article aimed more at the layperson but still informative. http://www.google.com.au/url?q=http://w ... ndDharJyrw I would also suggest horaldo, if not using the foil backed blanket then at least a perforated sarking under the roof. Stewie Thank you thank you thank you Stewie We get terrible condensation at our place in the wintertime And I have been looking for an answer to this for so long. This is the most useful information anyone has ever given. Planning to get my husband up on the roof on the weekend! (So not quite as much thanks from him I imagine) Given we are in cold climate it seems the answer is to improve the ventilation of the roof space and To vent the moisture sources directly outside (For us clothes dryer and bathroom). We previously got quotes to reroof and insulate and I now realise that the solutions they proposed would've made a problem worse! I need a 'cold roof' ie reflective foil layer (impermeable) on top of the ceiling, then bulk insulation, then just vapour permeable sarking (they had said blanket) under roof sheets. Will try the minimal option first and see if that does the job, Before reroofing Can't think the number of times I've googled this. to finally have an answer is so exciting! Can you give advice on how to get missing certificates needed for a form 21? Our bank requires us to provide one but we are missing 4 building certificates from our first… 3 71779 i would suggest nothing is unreasonable for PCI. we did all sorts, including checking the hot water, checking all the GPO's had power, testing that the showers were… 9 98623 Just to makea point about this, an approach that some people have found sucessful in negotiating these rises down, Is to provide some workings to the builder, specifying… 4 81667 |