Insulation first: why ECO4 often starts with the loft or cavity walls

By ApplyFreeBoiler.uk (Reliant Energy Solutions Ltd), an ECO4 heating and insulation installer in Bury, Greater Manchester. We are not the government, Ofgem or an energy supplier.

Many people come to ECO4 hoping for a new boiler, and are surprised when the first thing an installer talks about is insulation. This is not a sales trick. It reflects how the scheme is designed and how heat actually behaves in a home. This guide explains why the "fabric first" approach matters and what it means for your application.

Heat loss comes before heat supply

A boiler only produces heat. Walls, roofs, floors and windows decide how long that heat stays in the house. In a poorly insulated home, a large share of the heat a boiler produces escapes through the roof and walls. Fitting a new, efficient boiler into a leaky house still leaves you paying to heat the street.

Insulating first reduces how much heat the home needs in the first place. That can mean smaller heating bills, a warmer and more comfortable home, and, in some cases, a smaller heating system.

How ECO4 encourages this

ECO4 aims to lift the energy performance of the least efficient homes, measured using the home's energy rating before and after the work. Insulation measures often make a large difference to that rating, so they feature heavily in many ECO4 packages.

The scheme also has rules that link some heating upgrades to the insulation in the home. In many cases, a heating measure can only be funded if the property already meets minimum insulation levels or has that insulation installed as part of the same package. The exact rules depend on the measure and the property, which is why the survey matters.

Loft insulation

Loft insulation is usually one of the simplest improvements. Heat rises, and an uninsulated or thinly insulated loft lets a lot of it escape. The installer will measure the depth of any existing insulation and check that the loft has enough ventilation and safe access. Topping up to a recommended depth is often quick and causes little disruption.

Before the work, it helps to clear stored items from the loft so the installer can reach the whole floor area.

Cavity wall insulation

Many homes built from around the 1930s onwards have cavity walls: two layers of brick or block with a gap between them. If that gap is empty, insulation can be injected through small holes drilled in the outer wall, which are then filled. The installer will check that the walls are suitable, because exposure to driving rain, damaged brickwork or existing problems with damp can make some walls unsuitable.

Solid walls

Older homes, often built before the 1930s, usually have solid walls with no cavity. These can be insulated internally or externally, but the work is more involved and needs careful design to manage moisture. Whether it is suitable depends heavily on the building.

Ventilation matters too

Adding insulation makes a home more airtight. Without enough ventilation, moisture from cooking, washing and breathing can build up and cause condensation or mould. Good ECO4 surveys look at existing vents and fans, and a package may include ventilation improvements alongside insulation.

What this means for your application

Learn more

ApplyFreeBoiler.uk has plain-English guides to loft insulation under ECO4 and cavity wall insulation, including what the survey checks and how long installation usually takes. You can also apply through an obligated energy supplier or your local council via GOV.UK. Be wary of anyone who asks for a fee just to apply.

Published by ApplyFreeBoiler.uk, run by Reliant Energy Solutions Ltd (company no. 16100301), Bury, Greater Manchester.