GraHal

Damon, big Thank You! The 'HR25H Diary' is such a useful source of information on what it is like living with a single-room MVHR . I'm so glad you referred me to these. I'm saving the Tempra Blog (and the rest of earth site) for tomorrow with my breakfast!

Miek, is a heat recovery % quoted on your vent axia single room MVHR or have you ever worked it out (in and out temp diff etc?)? Or if none of above, can you feel the temp difference between in and out with your hand?

Thanks for both comments. Here are links to the 2 I refer to in my OP. https://www.ventilationland.co.uk/product/40954/decentralised-mvhr-unit-o100-mm-with-switch.html?utm_source=googleshoppingUK&utm_campaign=googleshopping-FeedUK&gclid=Cj0KCQiAic6eBhCoARIsANlox84gylzZ_oX2xqCYtogoCV8A0GZ1TTf19gNq_mMdtHpwf4c6Hu03sEkaAqhUEALw_wcB https://www.ebay.co.uk/itm/322917943393

Anybody got any thoughts on single-room MVHR or even anybody currently using? I have checked a few, one with ceramic heat exchanger and one with alumininium, otherwise they look same / very similar. I noted that the manufacturers don't quote a % for heat transfer outgoing to incoming air. Both above are quoted as 70 seconds extract, followed by 70 seconds fresh air in ... in and out down the same pipe. Others I've looked at, use a balanced flue (concentric pipes etc). Even if you are not using or not read up on them, any thoughts much appreciated. Thank YOu

Is there a top opener in the bathroom? If yes, screw a screw in the frame rebate so that top window is cracked open a tiny amount - 10mm or even 5mm, but can never be closed fully!! Tell them to ALWAYS keep the bathroom door closed Also open top openers in bedrooms during the day ... again a tiny amount makes a big difference, but does not cause drafts and negligible heat loss. Do existing windows have trickle vents (sorry if this has been stated?).

What Regs impact installation of MVHR? Accepting that ducts would be boxed in behind plasterboard and / or above ceilings. I keep thinking of ceiling terminals / air valves ... they provide a pathway from one room to others. Do the air valves need to be self-closing or have intumescent seals etc? Also any other comments gratefully received. Thank You

I'm not doubting, just interested ... what is the reasoning behind the above statement? Thank You