That is useful to know. I chose a Komfovent unit because of the wired TCP modbus interface.
Excellent. Where did you see this sensor so cheap? I can only see it for around £200.
There’s several on ebay for less than £100
Oh yes, just bought one. Thanks.
I’ll report back when I have it set up.
I’m looking at getting the Genvex connected. I can’t get the fall required for a normal drain, do you think I could just put in some condensate pumps?
Yes you can use a condensate pump. The main issue with these are making sure the noise of it coming on isn’t going to be an issue and finding one that isn’t going to fail after a while.
If house less than airtight are you just throwing money away. Your current air leakage is just being added too, it may be 85% efficient air leakage, but is still 15% more effective more air leakage.
Why not do a humidity controlled ventilation. Humidity activated trickle vents and wet room dMEV fans, that also respond to excess humidity smartly. Can be nearly efficient as MVHR as you only ventilate as much as needed, instead of a set flow rate 24/7.
Running cost, extract fans only not supply and extract, no filters to maintain etc.
MVHR is a balanced system (supply equals extract) so you are not adding to the leakage of the house.
The MVHR system itself does not become any less efficient in a more leaky house it will still sit there giving you reliable (i.e. not dependant on wind speed or direction or stack effect), filtered, pre-warmed (i.e. by the heat exchanging rather than cold air introduced through trickle vents) supply air and always extracting near where moisture is produced.
What does change is the proportion of air coming into or going out of your house that has come via the MVHR and heat recovery. The decision about whether it is worth it is working out at what point the benefits are swamped by the cold, unfiltered, variable air that is leaking into or out of the building.
At some point the house can become leaky enough that extract only systems become a better option. With MVHR it is so efficient that there isn’t much point making the system too complex with loads of sensors and dampers in a domestic setting. Yes extract humidity sensors are an easy win and are reliable. The likes of CO2 sensors can be useful in settings where occupancy varies a lot like offices. However with extract only systems it is worth adding more sensors to reduce the amount of unnecessary extraction as all the heat in extracted air is wasted.
In a more leaky house one benefit MVHR still has over MEV is that you know the supply rooms are being ventilated. With MEV you are designing extract points in wet rooms (in the same way as MVHR) but the supply air is assumed to be provided through background ventilators (window trickle vents or wall vents). But when the house is less leaky you have no way of knowing that the air being extracted is being replenished from air coming through those vents. It could be short circuiting through leaks nearer or within the extract room.
A good article talking about MVHR and its relationship to airtightness is this The Case for MVHR • Passivhaus Trust
Hi Glyn, One thought that occurs to me if you’re planning on mounting the MVHR in your roof space is that as well as building an insulated cupboard around it for both thermal and acoustic isolation, you should consider carefully how you mount/support the unit itself. Think about resilient mounts or suchlike to isolate the MVHR vibration and noise from your roof structure.* Any noise that gets conducted into the structure will likely be very bad news.
We have a HEPVO trap on our unit, which works well. We have three wet rooms and only two people normally, so we have to pour water down each shower every month to stop the traps drying out!
edit: * not that I think the unit will be particularly noisy, but you’ll be more aware of whatever noise there is than anybody else 