On Wed, 04 Oct 2006 11:59:39 +0100, Broadback
wrote:

Recently I have had loft insulation installed, the "surveyor" maintained
that even though there was no obvious form of ventilation it was not
needed because the roof felt was a breathable membrane, looks like
ordinary roof felt to me.
Anyway 2 questions, when is the best time to check for condensation, in
warm damp weather, cold, or when?

Cold, any humidity in the loft will condense on the coldest places.

Second if I need ventilation I intend to put through air bricks at
either end of the gables, does it matter how high they are placed?
TIA

I cant think of a reason why it would matter. I put one in lowish as a
trickle vent an am going to see what happens. If I still get
condesation I'll put a tile vent in the other side so I have hot air
leaving at the tiles cold air entering at the air brick convection
thing going.