No sleeved vents to crawlspace - having CWI done

[danped]

I am going to have cavity wall insulation (polystyrene beads) installed soon, my house has a suspended timber ground floor. The outer leaf is sandstone (on two sides) and rendered block on the gable ends.

On the outside there are airbricks every 2m or so which I assumed was to vent the underfloor space. However on closer inspection none of these vent to the underfloor space they simply vent the cavity.

Having been under the floorboards for a look I notice it is draughty enough down there to vent the floorboards. I think this is because there are plenty of gaps (not by design) between joists and the cavity.

I am committed to getting the CWI done as the house is very draughty and too cold. However I am concerned that the ventillation to the underfloor will be blocked because there will be no cavity airflow, and there is no ventillation by design.

I am thinking I need to add some sleeved airbricks through to the underfloor to retain airflow.

Do you agree? and how can I assess how many I would need?

Thanks,
Dan

 

[ban-all-sheds]

CWI will do absolutely nothing to stop draughts.

 

[danped]

Slightly off topic, but a portion of my draughts are coming from the cavity, e.g. around window frames where the plaster doesn't quite meet the window or it has cracked away. Clearly in this situation if there is no air movement in the cavity there will be no draught from it. Easily remedied I appreciate without cwi.

Less easily remedied are the gaps between 1st floor joists and the inner leaf which cause draughts.