Mike Steel

That's where we need to get to JohnMo, set up and running nicely. As you said in your previous post, perhaps we need to find the balance in flow rates. I don't think we are over thinking it, just not sure it's working at the optimum balance yet and listening to others who have years of experience with their systems, is much appreciated.

No there is nothing externally to control the air flow except boost, or turn it off completely.

All really useful info from people who have used MVHR for much longer than us. Having never lived in a house with it before, it's inevitably a little bit trial and error and hearing about how some have developed their own optimum settings is helpful. We feel our heating and MVHR are working against each other and so the next step is to accurately measure the air exchanges to see if they are set to building regs. Still not sure how buildings regs vs house air tightness work together because if we were at Passivhaus standard (which we are not) it seems the system would still be set at the same flow rates. That seems odd to me. I've bought a basic air monitoring device off Amazon to try and measure air quality with the MVHR on and after turning it off for a few hours during the day. Needless to say we've never needed the boost function, far from it - we can feel and hear air entering through the vents. And the bathroom soon clears after a shower. If we find the rate of air exchanges is correct as per regs, then I guess we'd need to consider a way to reduce the fan speeds. Over ventilating the house would seem like a waste all of the hard work and money invested in insulation and air tightness. Thanks again to all for sharing info on what you have found using your own MVHR systems.

Thanks for that additional info ProDave. The 4 speeds you have on your system, are they intended to be adjustable by the user, as we don't appear to have any adjustment on ours. Unless there is something deep inside the unit which I assume we should be leaving well alone.

Thanks NSS, that's useful intel. How do your described settings compare to how it was set up or instructed to be set up by the manufacturers info/building regs. And how did you determine what was right for you? Apart from the obvious such as cooking smells, did you have some kind of air quality monitoring to find a happy balance? I might be missing something but I'm not aware of how our fan speeds can be adjusted as you and others have described. As far as I know, they are fixed. Which MVHR system do you have out of interest?

The thought had crossed my mind. We'd have to establish a way of controlling the air flow. When you describe keeping it comfortable, how do you measure that? Currently we can hear and feel the incoming air. The heat recovery is fairly good, but the volume is high so it's noticeable. What would be the signs there is insufficient fresh air entering the house?

Out of interest how long have you run your system slightly lower? I was looking at what building regs document F stipulate the other day in terms of minimum ventilation rates. One of the things that occurred to me was if the MVHR has been set up and balanced to meet building regs, should the MVHR ventilation levels take into account the level of air tightness achieved in that particular building? Presumably if a house is not as air tight as the next one, surely it will be providing some of the required ventilation naturally through fabric leakage, without the MVHR needing to be set to deliver 100% of what building regs stipulate.

Thanks ! It's a Rega unit.

No, as far as I know it has nothing like that. The user options are to have it switched on, or off, or boost mode. All via traditional 240v switches. It does have a summer bypass function which is controlled by thermostats on top of the unit.

Hi all, We've recently self built and fitted MVHR for the first time, enjoying the constant fresh air! Like many other components with self building, the learning curve is steep and now we in the house we are reflecting on some of the many decisions we made and if given the time again, we would do some things a little differently. MVHR is a good example. The system we chose certainly appear to flood the house with fresh air but is perhaps fairly basic by comparison to some others on here in it's controls. Our system is either on or off with an additional boost function if required. Having read on here about other systems where you can effectively reduce the volume of exchanged air depending on occupancy, holiday mode etc I'm wondering if we should have gone for something more sophisticated. There's no doubt our system brings in plenty of fresh air, but we cannot help thinking its almost over preforming. Just wondered if anyone else has found the same and what they did aside from installing a new unit. Regards, Mike.