ARC Retrofit Eaves Insulator

• Ensures excellent insulation up to the wall plate.
• Maintains 25,000 mm2 ventilation area at the eaves detail as required for cold lofts.
• Minimises thermal bridging at the eaves detail.
• Reduces the psi-value and improves the thermal performance of a property.
• Warmer internal walls reduce condensation and the risk of damp and mould formation.
• Innovative design ensures fast and easy installation.

ARC Retrofit Eaves Insulator has been specifically developed to tackle heat loss at the eaves junction in existing UK housing stock. This area, where a pitched roof meets the wall, is often difficult to insulate retrospectively due to tight space constraints, making it prone to excessive heat loss.

Traditionally, installers used mineral or glass wool in this junction, but this often blocked the essential ventilation path into the loft space, increasing the risk of condensation and mould growth. Estimating and maintaining a suitable ventilation gap can be challenging, and leaving gaps in insulation creates thermal bridges and cold spots on internal walls. These cold areas allow moisture in the air to condense, leading to damp issues and mould formation.

The ARC Retrofit Eaves Insulator overcomes these issues by ensuring continuous insulation while maintaining proper ventilation, helping to improve energy efficiency and reduce the risk of condensation in retrofit projects.

Installation Guidance:

1. Remove enough loft roll insulation between the ceiling joists to access the eaves.
2. Fold the ARC Retrofit Eaves Insulator in half, keeping the plastic ventilation tray on the outside.
3. With the ventilation ridges facing upwards, compress the tray to expel air from the bag.
4. Push the unit into the eaves space, positioning the hinge of the ventilation tray into the corner of the eaves. The ridges should face upwards.
5. If access is restricted, use a pole or broom handle to push the unit into place.
6. Allow the product to expand naturally as air re-enters the bag. Once unfolded, ensure the ventilation tray ridges are in contact with the roof felt or underside of the sarking.
7. Lay loft roll insulation back up to the unit, making sure no gaps are left and that the ventilation path is maintained above the loft roll.
8. At the end of a run, if joist spacing is smaller, open the polythene bag, cut the insulation to size, reseal with duct tape, and install as normal.

What is the Retrofit Eaves Insulator (REI)?

The ARC Retrofit Eaves Insulator (REI) is a specially designed wedge-shaped insulating product with a hinged ventilation tray. It addresses heat loss and damp/mould risks at the tricky junction where a pitched roof meets the wall plate—especially in existing buildings where access is limited

What performance improvements can be expected?

By reducing heat loss at the eaves and maintaining proper ventilation, the REI significantly lowers the risk of condensation, mould, and structural decay—supporting both energy efficiency and long-term building health

Is it suitable for PAS 2035 retrofit projects?

Yes. The REI's dual function—ensuring both insulation and ventilation—is fully compliant with PAS 2035 requirements for sustainable retrofit projects