Slate vents installation during slate re-roof?

[MacLaverty]

We are currently having a Welsh slate roof re-done with new breather membrane, new lead flashings etc.

We have an attic bedroom so have 2 small loft areas either side. There is a small bit of condensation towards the bottom of the felt, near to the gutter, but just on one side and unsure whether to ask the roofer to put in some slate vents whilst scaffolding is already up or try some felt laps first as a bit worried that slate vents would make the attic bedroom absolutely freezing in the winter?

Any thoughts or best just to get slate vents to future proof?

 

[^woody^]

The new membrane should mean you don't need additional vents.

 

[MacLaverty]

There is a bit forming and the bottom of the felt, not sure if because if extreme weather or worth getting some vents just incase? Or do I just keep an eye on it for now?