Pete wrote:

I'm just about to get the felt on my flat roof replaced. I mentioned to the
roofer that it would be good to have better insulation.
He has suggested adding a vapour layer and an insulation on the top deck.

Having thought about it, is it going to do any good?
The roof consists of an upper deck with a 'void' of about 18 inches before
the lower surface which I think is made of chipboard.
There is an access hatch to the roof from within the house.
When it is windy, you notice a pretty strong breeze if you pop you head into
the void. Whether this is just for ventilation or whether we need some repairs
done, I'm not sure.

So if there is such a breeze in this space, isn't insulation that is above this
a waste of time?

Sounds like it.

I would have though the insulation should be in the void although this would
be more difficult to do.


Our flat roof insulation consisted of rockwool battens. We took down
part of the ceiling and slid them along between the beams, resting
directly on the plasterboard.

Ventilation is important, you don't want rot, but there's no reason to
have a gale blowing through, it will only make it harder to keep heat
in. You should find the source of this and control it.