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.

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

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.