sonicboom

Interesting, so the mvhr is passively heating that room. It is impressive whatever the case - 0.75c between exhaust/inlet which would make it 97% efficient ? Seems too good to be true. What make/model is your unit ? and what is the flow rate ? 18c is freezing btw, don't know how you survive.

Thanks - what is your internal temp ?

In my experience I have found wool insulation insufficient for pipework, primarily because its not dense and air can flow through it. I had some metal pipework that was losing huge amounts of heat under wool - 25mm pipe insulation fixed it.

Its currently running on its lowest speed. The house has a stale air smell in some rooms due to them being too tight. Speed 2 helps (there are 6 settings) but it gets very cold very quickly.

The house is a little too tight for extractors and PIV hence MVHR - The PIV is not as effective as it used to be and the improvements in heat retention just make it very costly to run.

Not bad 18.5c would be 92% if I maths is correct - Although, for 6.5c, I was expecting the efficiency to be a little higher. What does the WARM setting do ?

15c? that's a lot of heat loss, haven't you insulated your runs ? or maybe not enough ? what kind of duct work are you using ?

I am planning on upgrading my 10 year old PIV system to an MVHR. What kinds of efficiencies should I expect at current temperatures (-2.5c). My PIV churns out a draughty 7c and that is with the 400w heater enabled. i would ideally like something above 19c (internal temp is 22c 24/7). I have my eyes on the Zehnder Q350 which goes up to 96% but they do not produce charts on how that performance degrades as the temperature drops.