I want to buy a a heat recovery system for the bedroom

If the surveyor has ruled out penetrating damp and identified it as condensation, then improving ventilation would be the route I'd be looking at rather than thermal wallpaper. I've had good results with heat recovery units in the right property as they continuously remove stale, moisture laden air while bringing fresh air back in without losing as much heat. The important thing is identifying why the condensation is occurring in the first place, as poor ventilation, furniture positioned against cold walls, lifestyle factors and heating patterns can all contribute. A passive vent on its own often isn't enough if humidity levels within the room remain high. A heat recovery unit would generally be a better long term solution, particularly in a solid wall property where cold surfaces are more common. I'd also recommend checking relative humidity levels within the room and ensuring there are no hidden defects contributing to the issue before committing to any system.

Concrete floor is the problem Need to have a qualified Damp specialist Kindest regards Chris

Prior putting in a single room heat recovery other options should be taken into consideration. Why the vent didn’t work? Did it make the area colder? What is the temperature difference between internal wall and external wall? My experience is Kair heat recovery do work, if maintained and can be noisy and turned off in the evening where they are most required. I would suggest speaking with an experienced consultant in mould who looks at all the available options. If your London, homes counties based contact Damp And Mould Solutions