Insulating with tiny access

[psaffrey]

I live in somewhat draughty basement flat with sash windows. The windows have deep sills (about 500mm), like window seats.

I had some damp damage in a bedroom and had to remove a 200mm square hole from the plaster underneath a window. This is about to be repaired, but I'm wondering whether I should try to insulate the cavernous hole beneath the window, revealed by the hole. It's quite a small area of wall - only about 1.5m wide and 1m high - so it's probably not worth cutting out a huge section to get at it properly. I'm wondering whether I can use the small access hole to spray some foam insulation on the inside of the wall. It obviously won't fill the huge hole, and I'm wondering whether I'll have any success trying to get any kind of coverage with that awkward level of access.

Should I just not bother?

Peter

[Cicero]

================================== Do a 'google' (or Ebay) for polystyrene beads. They can be poured like porridge. Bear in mind that the hole you see might be an opening to a much larger cavity.

Cic.

[Andy Champ]

Did expanded mica go out of fashion? I don't like the idea of all that polystyrene in a house, it burns nasty.

Andy

[Appin]

The message from Andy Champ contains these words:

And the mice love it.

Mica was my first thought too, until I saw the location and the amount that would be required. Good stuff for stud partitions, but for my self I'd open up the area. It'll be easier to replace a larger piece of plasterboard anyway!