On Tuesday, 14 May 2019 15:47:13 UTC+1, George Miles wrote:

So I'd make the holes for MVHR and get it working without the complicated heat recovery stuff and see if that solves the condensation, if not put in more air vents.

The unit is installed and I just need to fit the manifolds and route the pipes - will probably get a good chunk of it done this weekend.

(may have to wait till winter to fully test it)

Yes, most likely.

a dehumidifier in the attic wouldnt be a long term solution,
anyhow with this week of hot weather it just needs lots of draughts and it will dry out.

Nothing feels damp in there at all. Indeed I've got quite a few cardboard boxes and they all feel fine; none have that 'weakened' feel to them that happens when they've got previously got damp/cold.

a humidity meter with hourly readings and a graph?

I will be controlling the MVHR with a Raspberry Pi so might add a temperature+humidity sensor for the loft to keep an eye on things.