Should I vent from a bedroom into the soffit

We have condensation build up on the windows in the bedroom. There are no trickle vents to open and I'd rather not leave the window open all year round.

Is it a good idea to drill holes above the lintel and put a vent from the bedroom into the soffit? Will that do "bad" things to the effect of the cavity insulation?

You can drill a hole high up and stick a vent on either side. The warm air will rise up and out, taking the moisture with it. Consider a built in insect screen on the outer vent, and a open/close inside vent.

Of course there will be some heat loss, and maybe a noise issue if there's a main road outside. but might still be better than condensation.

Either a big hole with a core drill, or lots of smaller ones in a concentrated area.

You might also be able to retrofit trickle vents.

Weigh up the P's & C's.

You really want to vent to fresh air.

The soffit is going to have lost of dust and possibly insulation fibres floating about

Don't you have a night/trickle position on the casements to enable them to be locked in a slightly ajar position?

Trickle vents can be fitted retrospectively to the frame - you just drill it and screw the vent covers on.

Many thanks for that. I'll investigate whether I can fit trickle vents, but if not will vent direct to outside.