Have just fitted some fixed (Easyfix superglaze) secondary glazing units to a wooden casement window which suffered badly from condensation.
The window itself had been painted shut, and I notice popular opinion is that the secondary glazing should be draft proofed whilst the external window should not. I have obviously not satisfied that guidance and still get some condensation on the internal surface of the window glass.
I assume the solution is to fit 'trickle vents', but can that be as simple as just drilling some holes in the external window? Should trickle vents be fitted BOTH to top and bottom of a window so as to encourage draft over the glass, or is just one required?