ᐅ Is cavity insulation effective with a 3 cm air gap?

Hello everyone,

Is it worthwhile to add insulation to a cavity wall after construction if the air gap is only 3cm (1.2 inches)? The facing bricks are also connected to the masonry (lightweight concrete) with steel ties. It is unknown whether there is any mortar joint providing additional connection. The air cavity is sealed, at least I don’t see any air vents at the bottom. At the top, the concrete slab rests directly on the bricks.

My question is, if insulation makes sense, which material would be best suited? Aerogel is ruled out due to the high extra cost. Definitely something that sets firm and does not crumble.

Also, can steel ties cause thermal bridging? If yes, how serious is that?

Thanks and regards

The steel pins do not create a thermal bridge. There is an insulation material made from recycled paper that is blown in. I am not allowed to mention product names here. In any case, they are treated flakes of recycled paper and also fill tight gaps because they are blown in.