Single room heat recovery in bathroom

Another beginners question about bathrooms. Is it worth fitting a single room heat recovery extractor fan in the bathroom. Perhaps not in terms of money savings but justified by CO2 savings? One day we may have a whole house heat exchange system, but right now we’re re-doing our bathroom. I have found models that run at 2W all day, to be honest that doesn’t seem right for a bathroom where you want to change the air quickly after a shower or bath. I’ll also seen models that detect humidity and run at different speeds accordingly - that sounds smarter. I assume they are less efficient at heat recovery when changing he air at a faster rate.

The quick answer is “Yes” but then as you point out, which type?


If you can reasonably duct the incoming air to an adjacent room you will then exhaust air that is partially polluted by household use rather than just bathroom use.

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There is a third variant, although it operates effectively just like 1.

  1. One opening, with continuous airflow in both directions through-teaffic a heat exchanger, warming the incoming air with the exhaust air.

The Vent Axis Tempra is such a system. I have one of those set up in an outdoor reptile enclosure to keep humidity under control and provide fresh air as best I can without wasting too much of their heat.

It was pretty easy to fit, is reasonably quiet on its lowest trickle seeing, has a manual boost switcj (or a humidistat control option) and can also do bypass to just exhaust with no return (I think it’s exhaust, it may be intake, worth checking that)

If I had an existing ventilation hole in the external wall I would have fitted one in our bathroom, but as there is no existing hole it would be a fair amount of work to add one and my retrofit plans have accelerated this year so am keeping the wall intact and opting for whole-house MVHR and ducting through the bathroom ceiling instead.

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When we refurbished our entire house we installed single room heat recovery extractors in both the main bathroom and the ensuite. There were all sorts of reasons why we did not know for a full MVHR, which was certainly right for us.
We went with this model:

which is one with a humidity detector and hence will up the power if the humidity goes over a certain level (which you can alter easily).
I have to say they have been universally excellent and I thoroughly recommend them.

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I have a kitchen where the oven and hob are in the centre island and the extractor fan is on the external wall and doesn’t really extract. Would this device manage the condensation in this scenario and would it help with humidity across the ground floor?

You definitely don’t want the extractor directly over the hob, particularly if it has fine tubules like a MVHR does as the system will get clogged with grease and particles from cooking.

One reason for not getting enough ventilation could be that the extracted air is not being adequately replaced and thus after a while with negative pressure the extraction stops at a new equilibrium. MVHR replaces extracted air so should resolve that, particularly if you can arrange ducting to allow extract and supply from opposite sides of the room or better still supply to an adjacent area.


The current arrangement is not adequately extracting from the kitchen, where the humidity is created and from where it pervades the whole house. It will be most noticeable in the nearest rooms. By preventing the buildup in the kitchen the whole house will benefit, not just the ground floor.

I would endorse this model (but ensure installer follows instructions). I took up Alan’s recommendation and also installed in bathroom and downstairs WC /shower room. Trickle ventilation with heat recovery and humidistat. Improves air throughout the smaller house, MVHR too intrusive and expensive. But have doors closed after shower/bath to reduce humidity

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I have a heat exchanger unit (100mm) in my kitchen and when I make jam there is high humidity that takes approximately 30-40 minutes to get rid of on boost settings when I close the door to the rest of the house. Similar operation to the bathroom with humidity back to normal within an hour. I know that there are larger units available (150mm). IAQ- Indoor Air Quality monitor also informs extractor use or window opening.

Are anyones heat recovery units mounted on a wall exposed to the prevailing wind? If i put one in my kitchen and bathroom, both would go on the most exposed wall which gets alot of wind, we are in Cumbria and quite high up. Our current only (useless) extract fan lets in huge amounts of cold air in when its windy (when its off). I thought I had read something about single MHRV not being good where its windy?- cant find the article now. thanks

I’ve not read about windiness being bad for single room MVHR or indeed extract fans but I can see that the angle of incidence could have a profound effect. Does either room have a less exposed wall?

It is probably worth talking to an installer to resolve by using a vent and bent exhaust duct- both increase resistance but can be modified to suit whilst reducing leakage.

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We are now ready to fit some sort of ventilation / humidistat in our bathroom. We’re removing the bath to gain floor space and for drying laundry. Our plan is to simply site the laundry airing rack in the bathroom and let the clothes dry at room temperature.
With this situation in mind, what type of dehumidifier would be best.
How would the Kair Single Room MVHR perform against a free-standing dehumidifying unit like a Meaco or an Ebac.
Would I see a huge difference in moisture extraction rates and running costs ?

I have experience of a Meaco and in an unventilated room it dries clothes quite quickly. I’d does, however use more electricity than my whole house MVHR. However the MVHR is slower to dry the clothes. I sometimes wish I could direct all or most of the extract to the drying room (bathroom) to speed up the drying, but that isn’t possible. When the MVHR is on boost all extracts are on boost.

I have no experience of single room MVHR but there isn’t really a direct comparison. The dehumidifier removes humidity (and some other volatiles) but doesn’t give you fresh air.

Using both is a waste of money as the MVHR draws in fresh air with some humidity and then the dehumidifier “tries” to dry it.

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Hi, my main concern with drying clothes indoor is the length of time it takes (especially for heavy cotton and towels) and the duration of prolonged, raised humidity that can lead to mould survival and propagation (hours).


Very true but in winter/wet weather there is often no choice. People just have to spin the clothes at the maximum their washing machine can manage and then rely on removing the resultant humidity from the room(s) where the clothes are put to dry.

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I’ve really found this thread incredibly useful.
All the shared comments have helped us decide upon a single room MVHR for the bathroom.

As mentioned here, drying clothes in winter takes a long time to dry.
We know it’s best to dry clothes in rooms created for wetter conditions - so the bathroom is our best choice.
Re heat - we can’t afford to waste it - so recovering it makes sense and scores another point to the single room MVHR.
Finally, wanting energy efficiency - it’s clear the MVHR is even more energy efficient than the dehumidifier.

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please share how you get on!

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I’ve only just realised there exists this amazing forum, having been a member for many years!

@pottyone72 and @Jonathan_Whitehead - which single room heat recovery system did you go for in the end? Please do share! Thanks.

We’re looking to install one in our upstairs bathroom and another in the downstairs loo. I’ve been trying to do the research, but finding it a little overwhelming as we also have plumbing issues going on.

We recently bought a Meaco as humidity levels in the house are consistently too high, so it would be in addition to this.

Welcome to the forum @Laura_Gilchrist.

So that we can understand your requirements better please briefly describe your house and the rooms that you want to ventilate.

Edit: where are the bathroom and downstairs toilet relative to each other? Could a dual room extract potentially reach both?