Extractor fans and wet roof issues

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gedc

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#205067 28-Oct-2016 13:34

So around a year ago we remodelled the house and put in a new bathroom as well. We ended up with a nice double shower with high glass sides. It has 2 high flow heads and a dumper in the middle.

After some initial use it became obvious (even with just the single shower running) there was a fair bit of condensation collecting on the ceiling above the shower. This was probably down to a couple of things - the extractor was in the centre of the bathroom and the higher than normal glass sides to the shower were not conducive to letting the bulk of steam escape. With 2 heads running and / or the dumper the roof gets very wet, very quickly.

So I installed a 2nd fan directly above the shower zone- a manrose in line that extracts roughly 89l/s. This appeared to make some difference. We now have 2 fans running in the bathroom.

With the kids(teens) now taking more showers I've noticed by the end of the second shower ( probably 35 to 40 mins of showering ), even with both fans running there are condensation droplets on the ceiling above the shower i.e big drops of water hanging off it. The bathroom however is relatively steam free. They disappear and dry off over time.

The roof is painted in dulux bathroom and shows no signs of issues, mould etc but I'm keen to not have this water/ condensation issue occur.

Other things to note-

It's well insulated above the ceiling space.

I can't put a showerdome over the shower as it would just look daft. It's a fully tiled / glass enclosure roughly 2 metres x 1 metre set back into the wall recess.

The distance from the shower grille to external grille is approximately 3 meters.

I was thinking of swapping out the current manrose for either a centrifugal model or a pro model that both have higher airflows / extraction rates with the thinking they would pull more moisture out faster.

Prior to dropping several hundred and spending 3 hours squeezing around the roof, any ideas or experience if this will actually make a difference ? Is it possible ( short of having a tornado ) to extract suitable volumes of steam prior to it collecting on the ceiling ?

One last question. Could it be there isn't sufficient air getting into the bathroom. I noticed around the bathroom door / doorframe significant dust and grime where it seems to be sucking air from the hallway. Other than the gap below and around the door, there is no entry point for air into the bathroom.

Thanks for your thoughts

Ged

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#1659784 28-Oct-2016 13:38

Talk to a bathroom company about a bigger fan. Not sure what I have but it's two speed, when on high we get no moisture collecting. On low only a little. It seems to move about ten times more air than the gutless ones from a hardware store.

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richms

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#1659787 28-Oct-2016 13:40

Are you sure it is condensation and not just water splashing up and collecting? My shower on hard makes a hell of a lot of mist that will make anything nearby wet. Not condensation so not a problem of the surface being colder than the air or anything like that.

Richard rich.ms

mdf

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#1659789 28-Oct-2016 13:43

Can you describe the extraction system more? How long are the ducts? Are the fans mounted at the intake or midpoint? What louvres/grills etc do you have at the exhaust? Which way does the exhaust face compared with the prevailing wind? What diameter are the ducts and fan?

Can you operate just one of the fans at a time, or do both have to be in together? I'd be interested to see wherlther you were creating some kind of odd vortex effect with the fans fighting each other. No idea if that's likely or not. I've never seen a two fan bathroom configuration.

Airflow in could be a problem. Can you open a window or leave the door cracked as an experiment?

wellygary

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#1659811 28-Oct-2016 14:05

You can install products like hardiGlaze and other waterproof sheets as a ceiling lining,

http://www.jameshardie.co.nz/assets/Uploads/downloads/HardieGlaze-Lining-Instal-Manual-April-2014.pdf

shk292

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#1659859 28-Oct-2016 14:52

It sounds like you need a shower dome; that would solve your problem very simply

1eStar

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#1659949 28-Oct-2016 17:48

A shower dome doesn't need to be a dome. All it achieves is a barrier between the shower enclosure and the greater bathroom airspace. Extend screen glass to ceiling? Put horizontal glass ceiling in shower?

The other consideration is that condensation is caused by the water vapour cooling to form water droplets, therefore running a heater so that the exhaust air is warm enough to carry all the vapour will help.

mattwnz

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#1659955 28-Oct-2016 17:58

1eStar: A shower dome doesn't need to be a dome. All it achieves is a barrier between the shower enclosure and the greater bathroom airspace. Extend screen glass to ceiling? Put horizontal glass ceiling in shower?

The other consideration is that condensation is caused by the water vapour cooling to form water droplets, therefore running a heater so that the exhaust air is warm enough to carry all the vapour will help.

You can get a lot of mold growing inside the shower when you seal off the shower like that. I wonder if it is an insulation issue with the ceiling being too cold? I wonder if there is any insulation in the ceiling?

Jase2985

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#1659991 28-Oct-2016 19:01

mattwnz:

You can get a lot of mold growing inside the shower when you seal off the shower like that. I wonder if it is an insulation issue with the ceiling being too cold? I wonder if there is any insulation in the ceiling?

he does say its well insulated

mattwnz

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#1660018 28-Oct-2016 20:00

Jase2985:

mattwnz:

You can get a lot of mold growing inside the shower when you seal off the shower like that. I wonder if it is an insulation issue with the ceiling being too cold? I wonder if there is any insulation in the ceiling?

he does say its well insulated

Although it does depend on where the insulation is. Condensation is attracted to cold surfaces, so I presume the ceiling is one of the coldest surfaces in the room, if that is occurring when there is already good ventilation.. Often you get still get consendation on old style aluminium windows in a well ventilated space, but not so much on walls and ceilings..

gedc

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#1660041 28-Oct-2016 20:57

Thanks for the replies. It would be tough to put in a shower dome as the 'rain' dumper in the middle of the shower extends down from the ceiling about 10 inches. The ceiling is insulated with roughly 4 to 6 inch pink batts in the loftspace above. It will be the coldest part of the room I'm guessing. There is no heat in the bathroom as we put ducted aircon into the house and were advised not to put an outlet in the bathroom.

Hardiglaze is a good option I hadn't considered but having seen the good lady's face when i just suggested it, I'm not sure that's a goer :)

I'm thinking it's just the volume of steam hitting the roofspace and the extractor not dragging it all away in a timely fashion. A solution could be a bigger flow fan but I'm not sure what difference a 95l/s fan would have over and 80l/s etc.

I'll try a shower with the main bathroom door cracked open to see if it's an airflow issue i.e air not being sucked out as the room fast enought as there isn't enough inflow.

I could also double insulate the ceiling above as well.

Thanks again

Jase2985

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#1660047 28-Oct-2016 21:04

yes it could be there is not enough inflow, so you may have to either take a bit off the bottom of the door or install a vent in it

timmmay

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#1660054 28-Oct-2016 21:17

gedc:

Thanks for the replies. It would be tough to put in a shower dome as the 'rain' dumper in the middle of the shower extends down from the ceiling about 10 inches. The ceiling is insulated with roughly 4 to 6 inch pink batts in the loftspace above. It will be the coldest part of the room I'm guessing. There is no heat in the bathroom as we put ducted aircon into the house and were advised not to put an outlet in the bathroom.

Hardiglaze is a good option I hadn't considered but having seen the good lady's face when i just suggested it, I'm not sure that's a goer :)

I'm thinking it's just the volume of steam hitting the roofspace and the extractor not dragging it all away in a timely fashion. A solution could be a bigger flow fan but I'm not sure what difference a 95l/s fan would have over and 80l/s etc.

I'll try a shower with the main bathroom door cracked open to see if it's an airflow issue i.e air not being sucked out as the room fast enought as there isn't enough inflow.

I could also double insulate the ceiling above as well.

Is your current fan from a hardware store? They're generally gutless. The fan type I mentioned earlier is the size of a motorcycle tyre and moves 5-10X more air. Talk to a ventilation or bathroom company, you can't get them at standard hardware stores. I could go up into the ceiling and get the make and model if you like. I posted it on GZ once, here's the picture. If you want to search it was approx 8/04/2013 9:07:00 p.m.

tdgeek

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#1660069 28-Oct-2016 21:50

The OP bathroom sound very very similar to ours, including the Manrose.

Our fan has one speed. We don't get condensation. The shower is double, tiled, glass doors. The gap from glass door to ceiling is about 300mm.

Possibly an issue re the compatibility of size, above shower gap?

I'd actually like a shower dome in there. They are great.

gedc

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#1660091 28-Oct-2016 22:36

Hi timmay. That fan looks like an inline centrifugal fan. They provide significantly more airflow as well as pressure which allows for longer duct runs as well. I think this is the model here or equivalent.

http://simx.co.nz/product-groups/extraction-fans/in-line-fans/high-performance-centrifugal-fans1

I have the SF150S on this page

http://simx.co.nz/product-groups/extraction-fans/in-line-fan-kits/manrose-classic-shower-fan-kits

Your model - if it's the 200mm intake and exhaust pulls 2.5x the air than my current one. It will also cope significantly better on longer duct runs where the inline one will drop performance quicker.

Cheers. Lots to think about. I can get your model from local electrical merchants.

gzt

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#1660097 28-Oct-2016 23:01

gedc: One last question. Could it be there isn't sufficient air getting into the bathroom. I noticed around the bathroom door / doorframe significant dust and grime where it seems to be sucking air from the hallway. Other than the gap below and around the door, there is no entry point for air into the bathroom.

It is a possibility. There are lower grill/vent things available for bathroom doors in a variety of styles and sizes. The louvres on those require cleaning now and then. Small amounts of dust will tend to reduce airflow/velocity significantly.

Maybe try leaving the bathroom door open 100mm or so when you shower and see if that makes a difference before installing one.

I've seen bathrooms where there is a lot less air getting in than being sucked out. With the fans running for a few minutes prior to establish pressure you can often hear the pressure differential when you open the door.

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