On the strength of this thread and phone conversations with Envirovent, we ordered an Envirovent Heatsava 12v in 150mm size (because it claims 75% recovery against 67% for the 100mm one, otherwise identical flow rate etc).

Disaster - client ordered it taken out immediately, unfortunately before I could come and see for myself.

Client's description, as below, forwarded to Envirovent, expecting immediate response, but no sense of urgency there, so it's their fault that I'm now spreading the bad word by asking here for comment and suggestions about what could be wrong, either in installation/adjustment, or inherent. We do hope to get our money back, so need to build the case.

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"…the ventilator does all it says on the box: clears away odours, and changes the air in the whole top floor as you hoped it would BUT I'm afraid we don't like it and plan to have it removed asap so that the roofers can get on with tiling over where the outlet has been when he is here this week doing the rest of the work.

In its normal mode it is very quiet (though of course no noise is preferable to very little) but it makes a noticeable draught in the bathroom and also makes the bathroom noticeably cooler (presumably 25%, since the unit says it is 75% efficient as a heat exchanger?) than the ambient upstairs temperature. This means that one always has a slightly chilly impression when going into the bathroom and sitting on the loo eg. in a nightie at night one wants to hurry up and finish and get out of the bathroom to somewhere warmer! Then try a bath or shower and it goes onto boost - as noisy as an extractor fan, and it makes such a draught then that both sets of curtains and the shower curtain are positively waving in the breeze and being naked and wet all one wants to do is get dry and out of the bathroom as quickly as possible. Needless to say we want our bathroom to be a comfortable, warm, relaxing place to be. So, turn the unit off when having a bath or shower, you say. Well that doesn't quite work either because although (very frustratingly) we haven't an isolation switch at the moment Giles did try just taking out the fuse for that circuit at the fuse board - but air continues to enter the bathroom of course (it's like having a giant trickle vent permanently open) since there is no closing shutter as you would have on a switched off extractor fan - and this was noticeable even with warm summer winds blowing, so would be much worse in cold winter weather. This is all prompting us to return to our orginal feeling, which is that we don't want mechanical ventilation. We are quite happy to do it by opening windows as always (just long enough in winter for a change of air, not to cool the house fabric down)

We feel as things are the lovely constant ambient temperature we have been enjoying upstairs since all the insulation work has been done is now spoilt, with the bathroom no longer being a pleasant place to be in. Nor do we like having no control over our ventilation and we feel it is unnecessary to have it mechanically controlled anyhow (and why use electricty, abeit very small amounts, when it's not necessary and we are trying to save energy rather than use it in ways we didn't need before?)."

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What does the team think?

As I said, the 150 has identical flow etc compared with the 100 - it's just the diam available for, therefore effectiveness of, the larger in-wall heat exchanger bit of it - and slightly lower elect consumption.

Trickle: 6.5l/s, 0.42 SFP, 4.9W
Boost: 13l/s, 0.6 SFP, 15.5W.

Yes, very hearty attitude to ventilation!

Unit installed at far corner, away from bath, in 1650 x 2650 x 2300h bathroom.

6.5l/s equally of extract and input on Trickle "makes a noticeable draught in the bathroom", and at 13l/s on Boost "both sets of curtains and the shower curtain are positively waving in the breeze".

It should be poss (but can't get my head round it) to work out an averaged air speed for the bathroom, given its volume in m3 and the rate in l/s of both extract and input. Would that be a speed to cause "noticeable draught"?
Makes me wonder whether this 12v unit was getting over-voltage somehow.

As well as draught, "also makes the bathroom noticeably cooler ... than the ambient upstairs temperature".
At 75% recovery efficiency, input air will be 25% cooler than extract i.e. if summer night time indoor 18C, outdoor 6C, input air will be 15C.
Bathroom air temp depressed in that way would I think cause air mixing/exchange over a wider area than just the bathroom.
6.5l/s works out at 2.2 ac/h for the bathroom or 0.15 ac/h if spread over the whole 1st.Fl. - so effectively say 1.2 ac/hr for the bathroom, at 3K temp drop, extract vs input.
Would that cause " bathroom noticeably cooler"?
Again, makes me wonder whether recovery efficiency was anything like as high as 75%.

If all that is as intended by Envirovent, then the Heatsava obviously isn't a good idea in a bathroom.
Lack of any shutter for when the unit's switched off, is another drawback, in any location.

Thanks for the answer Envirovent, which is same as the email I just received. Best if I continue the discussion with you by email/phone, as well as inviting GBF members to pitch in here, which you may want to as well.

Just to answer the above:

Posted By: EnviroVent6.5l/s on trickle, which is almost imperceptible

is why I wonder whether this one was getting over-voltage somehow, as draught was "noticeable" on trickle.

Posted By: EnviroVentcould be that your client’s heatSava has been installed in the direct air path when they are in the shower

as stated, in far corner of room.

Posted By: EnviroVentthey have to understand that the room temperature will drop at night anyway

even on summer nights bathroom temp was unconfortably cooler than rest of 1st.Fl. - is why I wonder whether this one was recovering anything like 75% @ 6.5l/s; alternatively was recovering 75% (losing 25%) of much more than 6.5l/s.

Posted By: EnviroVentnot designed to heat the room

that's well understood.

Posted By: EnviroVentso far had none returned to us

I hope you may take this one back for examination, and generally try to diagnose the problem, so the significant complaint that's been reported here can be laid to rest and GBF members can have confidence restored, as well as clarification of how/where to fit and how to avoid pitfalls.

Does yours have a shutter that closes when it's not running, so it's not an open channel to outside?

We will be in touch directly to take this unit back and have our QA department have a closer examination to try to determine if the unit is faulty and where the problem is coming from.

Also interested in this as a means to insert ventilation into our listed stone farmhouse. Plans being put in at the moment are to use 3g units mortared direct into the stone surrounds without any opening windows. As my wife suffers from asthma was looking for filter units to control air flow and these units seem far cheaper than full blown MHVR units.

Disguise terminals as bird boxes?

Posted By: jfbso...... to resurrect an old thread.....

was the unit faulty?!

Finally ... yes it was.

This thread started by reporting an unsatisfactory Heatsava installation. Turns out the humidity control unit was faulty. So Heatsava's reputation may be considered unblemished - but with provisos.

The faulty humidity control explains why the unit went to hurricane-force full power the minute any shower started - with a good controller, the speed-up should be gradual and hopefully less extreme. They say they've redesigned the humidity controller, meantime, anyway.

However, the experience shows the Heatsava shouldn't be fitted inside the bathroom - but it's capable of treating a whole modest-sized top floor from any central location, like the passage outside the bathroom.

Even on lowest power (it is indeed then very quiet), it does create slight air movement, which is not what makes for comfort to a bathoom-wet body. Worse, because the 150mm model is 75% efficient (68% for the 100mm model), if say inside temp is 20C, outside 4C, the incoming air will only be warmed 75% of the 16K difference i.e. will be blowing gently at 4C + (75% x 16K) = 16C.

So Heatsava's prob good, but watch where you site it.

Like Viking House's one unit per floor ductless MHRV units, also not sited in bathroom, capable of controlling water vapour even from a distance.

Don't suppose your bathroom walls are Warmcel, sheep wool or other organic insulation? Those alone wd make bathroom dehumidification almost unnecessary, as those hygroscopic organics absorb humidity peaks, for slow release later.

Contact Envirovent, see what they say about bathroom siting - that's just my own conclusion from the affair. Read the first post in this topic, to see what happened.

Posted By: fostertomDon't suppose your bathroom walls are Warmcel, sheep wool or other organic insulation? Those alone wd make bathroom dehumidification almost unnecessary, as those hygroscopic organics absorb humidity peaks, for slow release later.

Isn't it more to do with the surface covering? Don't tile the whole room, and use clay or lime plaster. (lime in wetter areas)

Lime's not hygroscopic (is it?) - clay plaster is, and will do the same job. Warmcel or other organics work through plasterboard/skim, which is almost vapour-transparent - until impermeable paint is put on it one day.

Is that continuing hygroscopic, of just during cure? If continuing, that's more good news.

What direction does the Envirovent Heatsava send the incoming air?

Fostertom,

Can you remember what wall the Heatsava was installed on relative to the location of the shower?

(I have a feeling that the cool incoming air may be send along the wall the Heatsava is installed in, rather than out into the room.)

It is a shame that there is not a small built in electric heater that is controlled by a movement detector or from the light switch….

I have yet to decide if I will use them, but…

Most of my en-suite bathrooms are long and thin, with the toilet at one end and the shower at the other. The end the toilet is at is on the outside wall. I also will have a heated towel rail that I may be able to position to heat the cool air.

Another option I am considering is the HR100R, boxed in over the WC with its “input duct” running into the bedroom. (Shame it cannot be mounted on its side to a wall.)

Or just a normal 'trickle' extractor and trickle vents in the bedroom window.

I have 5 en-suite bathrooms and 1 separate bathroom to design for. Due to sound and fire proofing I don’t want any ducts leaving bedsits hence not being a centralized system in.