In a Passivhaus/EnerPhit retrofit what ballpark target u-value should I be working to for existing party walls?

Solid brick walls. Leaky? I guess so, let's just say our EPC is G-rated. They're domestic neighbours on each side but one is often away.

Not even a little, not even on the 'often unoccupied' side?

Rgds

Damon

The air-tightness tests on Sheffield City Council's 'eco terrace' (written up as a case study by EST) found staggering air leakage through the party walls.

Tony, pretty certain they weren't. The houses certainly had solid walls front and rear and, based on experience of refurbishing probably more than 50 in that area, party walls were generally either 9'' solid or even 4.5''!! (Our habit of creating internal bathrooms between the front and rear bedrooms caused the neighbours to complain, just a little, as they could hear our tenants peeing!).

I'll have a look at the case study though, in case I am wrong.

Edit: Just checked. Not dreaming. s6.2 of the case study states: ''The most surprising air leakage
though was through the solid brickwork party walls.''