Cavity wall insulation

[AlanC]

We have just had a quote for cavity wall insulation for our 1989 built detached out. With current schemes it comes out at =A395, which sounds quite good. The quote was for polybead insualtion which I beleive is polystyrene balls.

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 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 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'.

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

Thanks

Alan

[Invisible Man]

Could depend on where you are in the country. We are in Essex which is very dry and have no problem with blown fibre. Have also lived in houses with beads that were not stuck together.

If you want to change anything that involves making holes through cavity walls do this first. Balls and blown fibre both have a habit of finding their way out of small holes eg behind meters and consumer units.

[John Rumm]

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

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

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.

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.

[NT]

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

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

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

Work out what it saves.

NT