Bit off topic but here goes. My street is on a slight incline and as such my house, which is on the end is set lower than pavement level and it gets very cold and damp so I've done all the usual stuff but I've noticed my bay window is incredibly cold and wet through having replaced it at the beginning of the year. The window sill is around 20mm thick wood so I've got some "polyfoam" slabs to stick onto the bottom for a bit of insulation but I'm not sure how to fix them. Glue will most likely dissolve the foam, didn't fancy screwing it unless it's a last option, dunno about mastics/silicones. I've some own brand no more nails trying to hold the house number on outside which is failing miserably so I'm not impressed with that stuff. Any ideas?

Hi do you have cavity wall insulation?
If you have and getting damp and is cold you may have voids or the damp course may have been breached.
If you are still looking for fixings you are best off with hilti fixings or fixings for Kingspan which can be bought from sheffield insulations or may be even jewsons.
Or if you don't have cavity wall insulation you could try your local council or energy agencys and you may be entitled to it free or a low rate.

I don't have cavity wall insulation, I've heard loads of bad stories about it. The cavity is there for a reason and to block it up would stop the house from breathing.
The idea I have at the mo is to fix some insulation to the underside of the bay window sill as you can see the damp form on it. Its only 20mm wood.

cavity wall insulation stil allows your house breathing.
If its just for under the window you may be better of with some polystyrene and stick it with evo stick.
for any insulation its best to keep an air gap between the insulation and the board or sill.
If you wanted cavity insulation and worry about any form of water ingress look for ecobead or simular

I has cavity wall insulation fitted 25yrs ago,( polystyrene beads), the differance was amazing. I would imagine that modern materials would be better still?

[Edited on 9-11-09 by 40inches]

Cheers kj, interesting that.
You think evo stick will hold or dissolve though?

if you are using just polystyrene from the likes of b&q i think its about £3 a sheet about 25mm thick the evo stick will hold it.

[Edited on 10/11/09 by kj]

That's it. Cheers kj.

Try out the Evostick on a test piece of foam first. I think it will dissolve it.

use expanding foam to glue it.
my whole garage is glued with expanding foam and insulation board.

you should think twice before insulating inside, you may just get condensation on the cold surface behind the foam. External insulation is better as you keep the thermal mass of the bricks inside the warm zone.

No I haven't insulated inside. I've stuck the insulation slabs on the outside bottom of the bay window and have to say I'm really impressed. There's a load less condensation forms on the window now. I'm not having to squeegee it all off in the mornings