Rockwool in the wall with air????

i made a wall and filled it with rockwool. The walls width is 10 cm and the rockwool is about 8 cm. However i can easily stuff another layer of rockwool on top of it by pushing it more together. (less air inbetween the wool) Does this decrease the effect of the rockwool because there is less air in the wool??? or is it better to use that extra wool and give it 2 layers but in a tight space??? so or 8 cm wool in a 10 cm wall or, 16 cm wool with pressure fitted in a 10 cm wall ?? THANKS!! :roll:

Hai and welcome to this magnificant forum. First, update your profile so we'll know where yer @. THEN read them stickies in this threat to get you started... after that, if you still are in doubt, return here and ask again. good luck!