I live in a modern mid floor flat, only about 10 years old, EPC B, double glazing, good insulation, but my north facing bedroom is always freezing and I'm pretty sure it's the trickle vents. I can feel all the cold air that's coming in when I put my hand near the vent. When the heating is on, the bedroom does warm up, but it's like it all escapes immediately because it doesn't stay warm and I can't think of what else could be causing this.
At the same time, I understand the importance of trickle vents and I haven't had any condensation on my window at all which is obviously good. What can I do? I only have blinds so was thinking to maybe get some thermal curtains?