We have been building houses for hundreds of years with a cavity air gap of approximately 50 mil or 2” if you prefer between 2 layers of brick wall or with a brick veneer home of timber frame and an outside layer of brick etc. This cavity in between is therefore a reason to allow air to pass up between each layer, especially in older houses where this design is meant for the air from the subfloor to pass between the two layers of the wall and out through the roofspace makes sense doesn’t it?
Until some insulation company comes along and fills it with insulation fibre and blocks the air from the subfloor – what sort of problems do you think this can cause? All this does is make the insulation company rich and does nothing to further insulate the home rather causing more unwanted problems of subfloor dampness and increasing problems in the roofspace.
This is just another example of bad building practice and rorting of the homeowner.
The ideal situation in this case is to leave things as they were allow the air from the subfloor to rise through the walls to the roofspace, then of course you will need a good roof ventilation system. This will evacuate the moist air from the subfloor through the cavity and out the ventilation system. This is also another way of cooling and drying the whole home system. So why would you block up this amazing solution to cooling and warming of the home with insulation that is going to do absolutely nothing but take your money and fill up with moisture and turn the subfloor into a swamp.
So in fact what will happen will be quite the reverse to what the insulation company said would happen.
Even when they build on a slab they still build with a cavity. It is therefore a reason so leave it alone and contact Universal Tile Ventilators for the best roof ventilation systems in the world to finish the job with effective balanced roof ventilation.