Air bricks for insulated cavity wall

[Bosi]

Hi. 

 

We have a 1950 house which got several years ago cavity wall insulation. After a recent extension most of the ground floor has been filled with concrete flooring and underfloor heating, and the areas which still have wooden floorboards have each an air brick for ventilation. 

After the extension the builder blocked the air bricks to the concreted area as they where not necessary anymore to his opinion, especially with the existing cavity wall insulation

The renderer now asked me why we don't have any ventilation for the cavity? 

So I start to wonder if we need air bricks for the insulated cavity area or not? 

Or should I put some drill weep vents in? 

Thank you for your help in advance. 

Greetings

Manfred