Cash wrote:
Steve Bilton wrote:
I went up into the loft yesterday to search out the Christmas Decs,
and discovered that the roofing felt on the underside of the roofing
tiles has condensation on it - to the extent that there is a line of
drips along the loft floor boards where the condensation has dripped.

The loft is well insulated with about 8" of rockwool, except where the
loft boards are, where there is about 4" underneath the boards. The
soffits were replaced last year with ventilated soffits and I can see
light at the edges of the roof when in the loft with the lights off,
and the air bricks in the gable walls are clear - free from
blockage/obstruction.

What do I need to do to stop the condensation? The only source of warm
air I can think of is from the loft hatch which has draught excluder
around it as it can't be insulated due to the loft ladder.

Do I need to improve the air flow? If so, how? or are there other
things that I need to do?

Ta

Steve

Steve,

It's interstitial condensation and more ventilation is required (possibly a
couple of tile vents on either side of the roof [in the middle] to create a
cross-flow of ventilation).

Cash



So a cross flow of freezing air at 90% relative humidity will dry it out?