On Jul 3, 1:53*am, John Rumm wrote:
AlanC wrote:

I have been doing a bit of googling and there are lots of different/
conflicting opinions on the best type of material and whether cavity
wall insulation is a good idea or not. *There are lots of people
reporting damp problems after they have had it done (some may have
been down to blocked air vents I guess). *It appears that the prefered

Some will be due to areas of uninsulated wall attracting heavy
condensation - either due to incomplete fill in the first place or the
filler slumping later. In areas with very wet outer walls then avaoiding
any material that can track moisture would also probably be a good plan.

running a dehumidifier costs a fraction of the money saved by CWI.

(I would expect poly bead to be ok in that respect however)

I tested some, it sucks up water quickly. So not really suitable for
walls that do get water in the cavity.


material is the polystyrene beads but I have seen reports that it can
cause problems with cables that are in the cavity. *We have satelite

Indeed it will. Polystyrene and PVC do not mix - it tends to leach the
plasticiser out of the plastic.

and network cables running in our cavity and mains cable that pass
through the cavity to the attached garage and external lighting. *Is
it still the case that this is an issue or was it just 'in the early
days'.

Still the case. It would probably be easy enough to sheath any power
cables passing through the wall. I would be inclined to take a chance
with the LV wiring. As long as its not being moved about too much it is
unlikely to be a problem.

You could work out what it costs to reroute the cables, and compare to
the cost savings - or just use a compatible insulator.


What are peoples general opinion on the different types of materials
and whether the cavity should be left as a cavity.

Generally most seem to find CWI worth having these days - especially now
the chemical foam products that used to be responsible for causing
irritation to the occupants don't seem to be used any more.

Work out what it saves.


NT