Retrofit Eaves Insulator

A cross section of the eaves of a red brick house with the retrofit eaves insulator installed. There is a black ridged ventilation tray above a triangle wedge of glass fibre insulation wrapped in green polythene, minimising thermal bridging and promotes ventilation.
Cold bridging product

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.
  • Variable widths suit all commonly found rafter spacings.
  • Patented hinge means the REI is suitable for all roof pitches.
  • Suitable for any existing building with a pitched roof, an eaves space and ventilation at the soffit or eaves where access to the wall cavity is restricted.
  • Ideal for PAS 2035 projects as ventilation and thermal performance are considered.


The ARC Retrofit Eaves Insulator was developed to address heat loss at the eaves junction of the existing housing stock in the UK. The eaves junction, where a pitched roof meets the wall, is a difficult detail to insulate retrospectively due to space constraints and therefore is prone to excessive heat loss.

Historically, mineral or glass wool was stuffed into this detail; however, this blocks the ventilation path from the eaves into the cold loft space and can result in mould formation and condensation in the structure.

If the installer estimates a ventilation gap, it is very difficult to ensure an appropriate ventilation path is maintained whilst fully insulating the eaves. A gap in the insulation at the eaves detail will result in a thermal bridge and a cold spot on the internal walls where moisture in the air can condense and mould will begin to grow.

Easy Installation

The ARC Retrofit Eaves Insulator is easy to install, ensures insulation right up to the wall plate, and maintains a ventilation path as required in the regulations.

The ARC Retrofit Eaves Insulator is to be used when continuous insulation from the loft to external wall insulation or the cavity is not possible. This may be the case when the path is blocked by a wall plate or the cavity is capped. The ARC Retrofit Eaves Insulator is best used when ventilation in the loft space is achieved through the eaves but can be used when ventilation is achieved by other methods.

The wedge-shaped product will ensure that the detail is fully insulated in any ventilation scenario.

Key Stats

Tray widths 300mm up to 600mm
Insulation Non-combustible glass mineral wool
Ventilation maintained 25,000mm2