On 01/01/2021 11:18, wrote:
Hi all and Happy New Year,

I'm trying to find the best solution to a condensation problem in a
loft in a 1980's new built block of flats (top floor flat with loft
access).

The condensation forms on the inside of the roofing felt then drips
down onto stuff stored up there. The loft is well insulated just
above the ceiling.

But not it would seem, equipped with a vapour barrier.

What you probably would find easiest is to board over the joists with
something impermeable, Foil backed plasterboard - extra celotex
insulation - or even just tack a plastic sheet over the insulation.

HOWEVER that does run a risk of transferring the problem to that vapour
barrier - the real fix is to have the impermeable layer INSIDE the
insulation. In short replace your ceilings with foil backed
plasterboard...or if the attic is rockwool between joists, lift that and
paste foil down (or lay a thick plastic sheet) on the plasterboard and
replace the insulation


I don't want to increase ventilation due to water
pipes being up there (as I don't want frost damage).


Insulated pipes with any water movement through them should be OK

Maybe some sort of screen fitted over the rafters or some kind of
insulation between the rafters? What would people suggest as a cheap
and easy to fit solution? It does not have to look good.

You are tackling the symptoms, not the cause. The cause is a combination
of too little ventilation and too little vapour barrier.

On reflection the simplest cure is to lift the insulation, lay down a
plastic sheet over the joists, and replace the insulation.

Make sure that any hatches are airtight and have a vapour barrier as well




--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.