Im looking to insulate the ceiling of the loft between the joists. The room is 4 x 4m has some airbricks in the walls (2 external with air bricks) and one has a window in which i leave slightly open for airflow.

 

So the question is how best to insulate?

 

Im guessing its PIR, if so any idea on depth?

Do i push it right to the floorboards?

Can i plastboard it out when done or best leave the joists open to breathe/airflow?

 

Thanks

Hi, confused with the title and question. Are you looking to insulate a loft or do something with a cellar?

Hi sorry, its a cellar but the ceiling of the cellar.

Jpeg attached maybe that makes it clearer?

Have to be very careful here, the previous owner of my house had put insulation between cellar and kitchen and it caused damp and rot in the floor and joists, I had to rip everything out and now heat the cellar and have no insulation at cellar ceiling. Result is a nice dry cellar and warm kitchen floor.