Energy Upgrade Options

Windows, Doors and Small Measures

Windows and External Doors

We found that older single- or early double-glazed windows and uninsulated doors leak heat and let in draughts, accounting for around 10–15% of overall heat loss. Replacing them with modern units achieving U-values of 1.2–1.4 W/m²K can reduce draughts, condensation, and improve comfort.
While thermal performance improves, the energy savings alone are generally small compared with installation costs — upgrades are most often driven by comfort, appearance, or maintenance needs.

When to consider:

• Homes with very old or draughty windows and doors

• Properties where condensation or comfort issues are noticeable

• Buildings due for maintenance or aesthetic upgrades

Smaller Measures (Lighting, Controls, Hot Water Efficiency)

Alongside major upgrades, we found that smaller measures deliver valuable incremental savings. Switching all lighting to LEDs reduces electricity use for lighting by up to 80%, while installing smart heating controls typically cuts heating demand by avoiding unnecessary use. Hot water cylinder insulation and low-flow fittings also make a noticeable difference. These measures are low-cost, simple to install, and provide consistent small improvements across all homes.

When to consider:

• All homes seeking easy, low-cost efficiency improvements

• Properties with outdated lighting, controls, or hot water systems

• Houses where quick wins are desired alongside larger works