Loft space - cavity wall - To cover or not to cover

First fix the insulation and leave the cavity to breathe as the cavity may be coming from underneath the floor and breathing through the wall so it cannot be covered.

Hi ya I have seen this question a few times , airflow needs to flow , as a installer my self cavity should be left clear

Loft insulation should finish at the cavity (outside edge of the internal skin) as long as this maintains at least 50mm air gap between insulation and roofing felt if you have a vented roof. If not you can extend your loft insulation out a little further if you wish as long as the cavity isn’t fully covered.

❗️ No – you should not block or bridge the cavity air gap at the top of a cavity wall with insulation. 🔧 Here's Why: 🔹 1. The cavity is designed to ventilate & drain moisture The 25–50mm gap between the inner and outer walls is there to: Stop moisture transfer from outer to inner skin. Allow air circulation and drainage if water penetrates the outer wall. Blocking it could: Cause damp issues by trapping moisture. Create cold bridging or internal condensation. 🔹 2. What you should do when insulating near the eaves: Run insulation to the edge of the ceiling joists (not over into the cavity). Use a baffle (eaves ventilation tray) to: Maintain airflow from soffit to loft space. Prevent insulation from spilling into the cavity. 🧰 Example product: "Manthorpe G502 Eaves Vent Tray"