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Topic # 124676 15-Jul-2013 21:04
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Trying to get some different opinions here. What do people think about putting ducted heating outlets into a bathroom?

I have had a few different suppliers provide quotes and suggestions, we have a largish bathroom & ensuite. The suppliers are fully against it or really think it's a great idea.


Reasons I was provided were:

Pros are the bathrooms are warm and are otherwise a cold trap in the house (cold draft etc).

Con is if the system is running and you are showering the moist air could get forced (sucked) into the house. I figure you could open a window and then the air pressure will force the moist air out that instead.

Does anybody have any experience with either?

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  Reply # 856162 15-Jul-2013 22:15
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Heated air into the bathroom helps with evaporating water, otherwise evaporating water will cool down the bathroom (liquid transition to vapour absorbs energy) which is why bathrooms are often cold. But I would still run the bathroom vent fan while showering to get steam out of the house.

Forced air circulation will also help distribute the moisture through the house instead of concentrating it near the bathroom, which with an en suite will give you lots of condensation in the master bedroom. I'd rather have little condensation throughout the house instead of lots in the master bedroom (which then gets cold in the morning when the moisture evaporates).

Our home is significantly dryer and warmer since I've installed my reverse heat transfer system (suck air out of bedrooms, blow it into the living space where the heat pump is). I'm surprised how much condensation reduced without venting (would be better if the kids did not leave their wet towels in their bedrooms).




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  Reply # 856234 16-Jul-2013 08:15
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You would still need moist air extraction, ideally directly over your shower. Put the heating input nearer the door.

I have under tile heating, which isn't meant to heat the room, but does a little. I also stuffed the bathroom walls with as much insulation as they could take, and installed a double glazed window. You can put a baffle thingy in the extractor pipe to stop cold air blowing in.




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  Reply # 856262 16-Jul-2013 09:36
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have you checked out shower dome?

edit: would that compliment what your trying to do with regards to heating the bathroom?



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  Reply # 856286 16-Jul-2013 10:17
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Taking a step backwards, what are the implications of positively pressurising a bathroom. The volume of air you pump in needs to flow out, so you'd need to give some thought to that. Ideally you want the moisture out of your house, not distributed throughout it.

A bathroom should have some extract process. I think what you are proposing could work, but you'd need to keep your bathroom door shut, then the air would flow into the bathroom and be able to push out through the extraction duct. Which leads to, why would you want to effectively pipe the air you've paid to head straight outside.

Personally I'd stick with a more standard way of heating a bathroom and only involve air movement as an extract only on demand when required, ie only run the extract for 20 minutes or so during/after having a shower/bath etc.



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  Reply # 856287 16-Jul-2013 10:27
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Jaxson: Taking a step backwards, what are the implications of positively pressurising a bathroom. The volume of air you pump in needs to flow out, so you'd need to give some thought to that. Ideally you want the moisture out of your house, not distributed throughout it.

A bathroom should have some extract process. I think what you are proposing could work, but you'd need to keep your bathroom door shut, then the air would flow into the bathroom and be able to push out through the extraction duct. Which leads to, why would you want to effectively pipe the air you've paid to head straight outside.

Personally I'd stick with a more standard way of heating a bathroom and only involve air movement as an extract only on demand when required, ie only run the extract for 20 minutes or so during/after having a shower/bath etc.


we will still have an extraction fan going when the shower is in use. What I was trying to work out is having vents in those rooms considered bad as I have had mixed feedback from the different suppliers.

At the times when the heating system is running and we have a shower (might not happen all the time). I figure that if the door is closed, and we are extracting similar amounts of air as we are putting into the room then it's less likely the moist air would flow into the house. your right that we would lose some of the heat we are generating. 

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Master Geek
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  Reply # 856288 16-Jul-2013 10:28
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A cheaper way to do this is install an above the shower extractor fan (you can get them with a nice downlight from Bunnings), and because the fan is inline and not above the shower (and the light is less than 12 volts) you can install directly over the shower for maximum extraction. When you shower, close the window and leave the door slightly ajay. This will draw the warm air in from the bedroom which will result in less steam (sucking cold air in through the window increases the steam immensely). Leave the fan running for five minutes after showing (some have timers built in) and you should have a nice stream free and dryer bathroom. I wouldn't recommend circulating moist bathroom air around the house, if it was a good idea, there would be off the shelf solutions available.




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  Reply # 856289 16-Jul-2013 10:30
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Since you're making the bathroom lower pressure because of the extractor you may find a lot of heat flows into the bathroom when the fan is on, less to the rest of the house, and you're basically putting hot air outside. If there's a way to enable and disable it that might work, but it'd have to be physically closed.

I suspect a fan heater is a better idea. You can get dual wired ones so instead of 10A you can put 20A through them, as 10A is ok but takes some time to warm a room.

Generally we keep the bathroom door open most of the time, so it's as warm as the rest of the house. It just needs a little boost before the room is used, in winter.




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  Reply # 856290 16-Jul-2013 10:32
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MattEast: A cheaper way to do this is install an above the shower extractor fan (you can get them with a nice downlight from Bunnings), and because the fan is inline and not above the shower (and the light is less than 12 volts) you can install directly over the shower for maximum extraction. When you shower, close the window and leave the door slightly ajay. This will draw the warm air in from the bedroom which will result in less steam (sucking cold air in through the window increases the steam immensely). Leave the fan running for five minutes after showing (some have timers built in) and you should have a nice stream free and dryer bathroom. I wouldn't recommend circulating moist bathroom air around the house, if it was a good idea, there would be off the shelf solutions available.


Bunnings extractors and extractors inside lights are really pathetic and underpowered. They just don't move enough air to be useful.

In my old bathroom I had two proper extractors from bunnings running side by side, with two holes in the ceiling, that worked well. Our new bathroom has a two speed commercial extractor - hot onto your hat, it may get stuck in the vent when it's on high.




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  Reply # 856307 16-Jul-2013 10:50
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Our bathroom is quite small so their units are suitable for our purposes, however if you have a large space you may want to look at higher capacity units...installing above the shower does help remove the steam at the source. Also keeping the length of the ducting as short as possible also reduces resistance (hence increases the extraction rate)




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Ultimate Geek
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  Reply # 856308 16-Jul-2013 10:51
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All I can go by is from what I have seen (and did) back home in virtually every modern home. Bathrooms have a ventilation fan (extractor fan) and are heated via -

Electric Baseboard Heater
Hot Water Radiators (Oil Furnace)
Heated Floor
Forced Air Heater Furnace

The extractor fan was only ever going during a shower and for a little time after the shower, maybe 60-90 minutes after a shower (on a dial timer).

I can't see any issue heating the shower room via forced air, as long as the extractor is going and the door is closed.

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  Reply # 856330 16-Jul-2013 11:43
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Azzura:

I can't see any issue heating the shower room via forced air, as long as the extractor is going and the door is closed.


Both Timmmay and myself have outlined a few potential issues, for example:

1) When the bathroom extractor fan is running, you're far more likely to draw lots of warm air from your bathroom outlet (instead of evenly distributing this out through the other duct outlets around the house).  Once in the bathroom all this warm air is then most likely pumped outside, which is hardly efficient/cost effective long term.

2) Your bathroom will still be wet after the shower period.  By heating the room you encourage the water into a vapour state, which is then being circulated throughout your house.  Yes this will dry the bathroom, but at the cost of wetting the air throughout the entire house.

The reason is OP is experiencing mixed reviews, is because there genuinely are some potential issues with the proposed scenario.  I'd advise determining what the underlying 'problem' is and working from there.  Presently you're mixing heating in with air distribution, which may not be the ideal scenario.

Ducted systems work by taking air from a warm location and 'pumping' it to other locations.  It doesn't stop at that though.  To work that air then needs to make it's way back to the starting location, to go around again.  The concern suppliers/contractors have is that you're now potentially drawing 'wet' air back through your house, rather than expelling it outside. 

There are real pros and cons to the approach you are considering is all.

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  Reply # 856334 16-Jul-2013 11:51
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I'm largely repeating what others have said.

Don't put heating vents in your bathroom, kitchen or laundry because these rooms have a microclimate which is primarily moist.  Instead duct heated air into rooms that are predominantly dry.

To heat up moisture, which is water, by 1C takes a lot more energy than heating the equivalent volume of dry air. This means that:


  • It is generally more efficient/cheaper to extract moist air from a room before heating it.



  • Areas producing moist air should have a vent for moist air to escape.



  • Ducting warm air into a room that has cold moist air will reduce the effectiveness of your heating.


Ducting air into a room increases the air pressure (positive pressure) and forces the air into areas with lower air pressure. This means that:

  • Air ducted into a moist room will generally force moist air out into drier rooms like the bedroom or hallway.



  • It will usually be more efficient to place heating ducts in the room next to a moist room. The positive pressure from the ducted air will help keep the moist air in the bathroom and, with an external vent, will also allow moist air to be forced outside.



[Edited to try to remove extra blank lines placed by the editor]

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Ultimate Geek
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  Reply # 856363 16-Jul-2013 12:08
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If you're spending money on a ducted heating system, chuck in a balanced system with an air to air heat exchanger.  Fresh drier air from outside, and take the exhaust from the bathroom and kitchen etc...

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  Reply # 856370 16-Jul-2013 12:30
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Perhaps I misunderstood. But I was suggesting to vent it directly to the outside, not through out the house.

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  Reply # 856377 16-Jul-2013 12:38
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Yeah I'm not sure why people think moisture will go into the house, if the door's closed. Instead it will take all the heat being created and pump it directly outside, instead of evenly around your house. I think it's a bad idea.

A balanced ventilation system is a good idea - steam actually makes the heat exchanger work better, better contact and more heat to reuse. I like this company for a heat recovery ventilation system. Just don't put a vent in the bathroom. If you have heat in the hallway outside it it will draw warm air in around the edges of the door anyway, but at least the house will still be warmed.




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