Air brick in both skins- open to cavity, and cavity open at top?

[Safety First]

Is this normal for 1930's semi? If it was 'the way' back then, is there a change that we should consider for better energy efficiency?

For clarity, an insect could enter from outside air brick and either go into wall cavity and up out into the loft, or straight on through the cavity and into the under floor area.

If we sought cavity wall insulation, would it not just come out the top, and also into under floor void?

Thanks people

 

[John D v2.0]

That's how they did it then, if your cavity is clean you could get insulation put in, but you'd have to get the air bricks sleeved through to the void to stop it escaping and blocking the floor ventilation.
As it is, interfering with the balance of old houses isn't always a good idea especially if it's hard to undo.