Calling PigletJohn - insulation

[tentative3]

PigletJohn or anyone else in the know, can I just confirm something? I'm looking at laying knauf earthwool between the joists here after some new plumbing pipes are laid. This is the first floor of an old house. Can I just tuck it under any cables or pipes? I'm fairly sure I can but don't want to cause a fire risk!

A secondary question... Any ideas why we wouldn't have air bricks on this floor but do for the next floor up?

In some areas we're less sure though, don't think there is enough give in the cables, like this:

yes you can. Electricity cables can be under the insulation, or on top of it, but must not be buried or surrounded by insulation. It must not be in contact with hot pipes. You can guard against that by putting pipe lagging (stiff plastic foam) on the adjacent pipes. Not polystyrene, which degrades cable by contact. The pipes do not need lagging otherwise, as you can surround them with the wool. This is worthwhile for pipes in an unheated area such as a garage ceiling, loft, or under a ground floor, and for hot pipes heating a hot-water cylinder or supplying taps.

I recommend the mineral wool treated with Ecose (it is brown, not yellow) which does not shed irritant dust and fibres. It is made by Knauf but widely sold as an own-brand. The word "ecose" will be on the packaging. Winter has just finished so you may find half-price offers as the sheds try to clear their stocks of this bulky product. You can cut it with a fine-tooth saw (preferably before taking it out of the wrapper) to a width that will be a tight fit between the joists (it squashes to fit, but do not compress it down and reduce the thickness) or with big scissors, like wallpaper scissors, when released.

Hoover out the dust and rubbish first. If there are cracks or gaps, fill them with pink (fire grade) expanding foam. It is not expensive.

Here's one I did earlier.

p.s.

draughts are especially likely round the edges of the room, and they blow black dust under the skirting, which stains carpets. So clean and fill these with mineral wool well stuffed into the gap between joist, wall, floor and ceiling below. This is worthwhile even when you are not insulating the rest of the floor.

Thanks so much PigletJohn. Can I just clarify that it's the electrical cables which shouldn't be in contact with hot pipes?

yes.

Cheers