FAQ

Any concerning questions relating to grant entitlements, processes & what is required can be found here on this page. Click on the boxes to reveal answers to questions etc.

No, grants cannot be backdated. All information must be submitted during the application process & must be approved before any work is carried out.

A Heat Loss Indicator (HLI) is a numerical measure that quantifies how much heat a building loses through its structure — including walls, roofs, floors, windows, and doors — relative to its size. It gives homeowners, builders, and energy assessors a simple, standardised way to evaluate the thermal efficiency of a home.

The lower the HLI score, the less heat the building loses, and the more energy-efficient it is. Conversely, a higher HLI score indicates significant heat loss, leading to higher heating bills and a less comfortable living environment.

If you hold an existing BER Certificate, your HLI is shown on the advisory report that accompanied your certificate. It is typically located on page 3 of the report. Please note: Advisory reports issued prior to 2020 do not display the HLI.

The HLI is typically derived from a combination of factors assessed during an energy survey or audit of the property:

  • Fabric Heat Loss — Heat escaping through walls, roofs, floors, windows, and doors (measured by U-values)
  • Thermal Bridging — Heat that bypasses insulation through junctions, frames, and structural elements
  • Air Permeability — Uncontrolled air infiltration through gaps and cracks in the building envelope
  • Building Geometry — The surface area of the home relative to its volume (the more compact a building, the lower the heat loss)

The result is expressed in watts per degree Kelvin (W/K) or sometimes as watts per square metre per degree Kelvin (W/m²K), giving a measurable indication of energy performance.

Understanding your home’s HLI is a critical first step in making meaningful energy improvements. Here’s why it matters:

💰 Bills – A high HLI means your heating system must work harder to maintain a comfortable temperature, leading to significantly higher energy bills.

🌡️ Comfort – Poor heat retention leads to cold spots, draughts, and temperature inconsistency throughout the home.

🌍 Carbon – Heat loss is a major contributor to a household’s carbon footprint. Reducing your HLI helps lower your environmental impact. 

🏠 Value – Homes with better energy ratings (linked to lower HLI) command higher resale values and are increasingly attractive to buyers.

Most homes — especially older properties — suffer from one or more of the following heat loss sources:

Improving your HLI doesn’t have to mean a complete home renovation. There are measures at every budget level:

Quick Wins (Low Cost)

  • Draught-proof doors, letterboxes, and keyholes
  • Add draught excluders to windows and skirting boards
  • Install thick curtains or thermal blinds
  • Lag hot water pipes and insulate your hot water cylinder
  • Use radiator reflector panels on external walls

Medium-Term Improvements

  • Install or top up loft insulation to at least 270mm depth
  • Insulate your cavity walls (if applicable)
  • Upgrade to A-rated double or triple-glazed windows
  • Fit a smart thermostat to optimise your heating schedule
  • Seal gaps around floorboards and skirting

Major Upgrades (Higher Investment, Biggest Impact)

  • Install solid wall insulation (internal or external) for older pre-1920s homes
  • Upgrade to a high-efficiency heat pump or condensing boiler
  • Install underfloor heating with insulation below
  • Consider a whole-house mechanical ventilation with heat recovery (MVHR) system
  • Explore solar panels or other renewable energy systems to offset remaining demand

A professional energy assessor can calculate your home’s HLI as part of a home energy audit or SAP (Standard Assessment Procedure) calculation. This is commonly done when:

  • Applying for an Energy Performance Certificate (EPC)
  • Seeking grants or funding for home improvements (e.g., ECO4, Insulation Scheme)
  • Planning a renovation or extension
  • Assessing compliance with Part L building regulations (new builds)

You can also use online tools and calculators to get a rough estimate of your home’s heat loss before commissioning a full survey.

The Heat Loss Indicator is one of the most powerful tools available to homeowners and professionals for understanding and improving the energy efficiency of a home. By identifying where and how much heat is being lost, targeted improvements can be made that deliver real, measurable reductions in energy bills, carbon emissions, and improve overall comfort — making your home warmer, greener, and more cost-effective to run.