Understanding the ARC Retrofit Eaves Insulator

The Retrofit Eaves Insulator Vs. The Eaves Insulator

11th March 2024

The ARC Retrofit Eaves Insulator vs. The Eaves Insulator

We recently officially launched the ARC Retrofit Eaves Insulator, a non-invasive patented solution that looks to tackle thermal bridging in current housing stock; providing more habitable homes for the occupiers, decreasing energy costs and significantly reducing the risk of damp and mould in homes.

However, the eagle-eyed amongst you will have noted that we also manufacture the ARC Eaves Insulator. A similarly innovative product designed for similar reasons but used in very different applications. So when do you need the Retrofit Eaves Insulator and when do you need to Eaves Insulator?

The ARC Retrofit Eaves Insulator

The newest product developed by ARC and our first foray into providing solutions for current housing stock as opposed to new builds. The Insulator is designed to solve a number of problems caused by inadequate insulation at the eaves junction, where there is no access over the wall plate. Typically, this is a difficult detail for retrofit installers to reach and in order to sufficiently insulate the eaves installers either:

  • stuff loft roll into the cavity
  • jerry-rig their own device to use

Both previous solutions come with inherent issues which the Retrofit Eaves Insulator solves in one fell swoop.

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.

Poor Ventilation & The Duvet Effect

Simply stuffing insulation into the eaves detail will insulate the area, however this is at the expense of proper ventilation. In short, this creates what is sometimes referred to as the ‘Duvet Effect’. The air flow is stifled and this comes with a host of issues, chief of which is condensation in the loft space. As David Pierpont from the Retrofit Academy succinctly explains:

An insulation project without ventilation is a condensation project

Without delving into the technicalities too much, warm air can hold more moisture than cold air and when the moisture laden warm air lands on the roof fabric, it cools, depositing the moisture and forming condensation – just like your bathroom mirror when you shower.

Condensation in a loft with no ventilation hugely increases the risk of rafter rot. As the name would suggest, rafter rot is the degradation of the rafters in your roof space caused by dry rot. Research suggests that 80% of dry rot in a domestic setting is caused by poor maintenance, including insufficient ventilation.

As wood loses a great deal of its integrity when rot has set in, the rafters often have to be replaced before any further significant structural damage occurs. This is a costly process that could be avoided four times out of five.

The Retrofit Eaves Insulator’s Patented Hinged Ventilation Tray

The hinged tray on the Retrofit Eaves Insulator allows the solution to be used with just about any roof pitch, but more importantly allows for ventilation to be assured once the product is installed. Simply compress the Insulator, push into the eaves detail and allow to reinflate, the ventilation ridges provide routes for air to circulate and significantly reduces the risk of dry rot forming on the rafters.

This ventilation-come-insulation solution means the Retrofit Eaves Insulator is perfect for PAS 2035 projects which state that, in order to gain government funding, a solution must holistically consider both insulation and ventilation.

an image demonstrating how the retrofit eaves insulator is easy to install, considers ventilation and provides insulation at the eaves detail.

Thermal Bridging At The Eaves Junction

Of course, installers could just make their own devices by sourcing insulation and a ventilation tray separately before installing their put-together solution themselves. Anecdotally, this solution works in a retrofit scenario, however it is bereft with issues such as commodity costs, labour costs, and more importantly – will it actually work?

As with all our products, the Retrofit Eaves Insulator has been rigorously tested to ensure the solutions perform as we state their will. The issue with homemade devices is the lack of consistently and the inherent labour hours spent creating each insulator individually.

The Eaves Insulator

Unlike the Retrofit Eaves Insulator, the Eaves Insulator is a solution designed to be installed whilst a low-rise building is under construction and not retrospectively. It works in a similar way to the Retrofit Eaves Insulator in that it tackles the issue of thermal bridging at the eaves detail whilst ensuring sufficient ventilation in the loft space. Again, the whole goal is to create a sufficiently warm, insulated, and ventilated house with minimal thermal bridging and cold spots. Something both products are particularly effective in.

As the wall cavity is still accessible during this stage of the construction, insulation can be placed over the wall plate. Historically, this proved a difficult detail to insulate, and installers would stuff mineral wool over the ceiling trusses into the cavity. Correctly calculating the correct amount insulation needed and ensuring the correct compression has been achieved is nigh-on impossible. This ad hoc approach means there’s inconsistencies in the insulation, leading to heat loss.

Thus, the Eaves Insulator was born offering a 49% improvement in reducing the heat loss at the wall plate when compared to traditional methods.

A render of the Eaves Insulator sitting at the eaves junction. It features a black tray with ventilation ridges attached to a green bag of glass fibre insulation. The product is in-situ.




Mould In The Home

Both these solutions have been developed to keep houses inhabitable. Outside of the loft space, a common area for cold spots in homes is where your wall meets your ceiling on the uppermost floor. This is due to insufficient insulation at the eaves detail. What this leads to is condensation forming on said cold spots, much like the roof fabric and rafters in the loft space as already discussed. Moist areas within the walls of a home can lead to issues with damp and mould – an extremely prevalent issue with UK housing stock at present.

Awaab Ishak

Bringing houses inline with latest guidance and tackling mould is at the forefront of most housing associations, and with good measure. The impact on health mould can pose is massive, and sometimes even deadly – as in the tragic case of Awaab Ishak.

Public outcry following the death of the two-year old due to respiratory problems brought on by excessive mould in his home prompted the Government to pen ‘Awaab Ishak’s Law‘; a legislature that rightly ensures landlords will act swiftly to rectify issues cased by damp and mould. However, as always, prevention is better than the cure.

In ensuring mould does not have the opportunity to proliferate in the home by taking away the opportunity for it to grow, the problem is largely avoided. Both Insulators do not guarantee this complete absence of damp of mould in the home, but will significantly reduce the risk of mould and damp forming in the loft space and, importantly, where your wall meets your ceiling underneath the eaves junction.

So When To Use Which Insulator?

In short the answer is simple, if you are looking to correctly ventilate and insulate the eaves junction of a property currently under construction, the ARC Eaves Insulator is the correct solution. If you’re looking to ensure a holistic insulation and ventilation solution for the eaves junction of a house which has already been built, the ARC Retrofit Eaves Insulator is the right option.