Cold roofs without fresh air flow - how common is it?

[plockhart]

I have been looking at moving house so I’m doing a fair amount of viewings. Based in the north of Scotland, I keep stumbling upon cold roof houses built between the 60s-80s with no fresh air flow I can see. I have seen a few with cold pitched roofs with insulation at the joist level all the way to the eaves, and no soffit vents or roof tile vents. Then today I viewed a dormer with the eaves accessible with a hatch; where the insulation was between the rafters but the floor of the hatch extended to the eaves with insulation on top.

 

Am I missing something? I thought cold roof construction had to have fresh air flow? Evidently these properties were built like this from the start and haven’t had any mould/smells/damage. I appreciate it might be possible with a strict VCL on the warm side of the insulation but in the roofs I have been in I didn’t see any membrane or the like. Or is it because the roofs have less insulation (50-150mm rolls) so the condensation is happening under the roof tile and not under the sheathing, so it is ok?