Insulation first: Maximising heating systems through whole-house thermal efficiency

According to a 2024 House of Commons report, heating the UK’s 28 million homes accounted for 18% of the nation’s greenhouse gas emissions in 2021, with the main source of those emissions being the combustion of natural gas. Reducing emissions from home heating is therefore a critical part of achieving the UK’s net zero target by 2050. Improving the energy efficiency of the building fabric – through measures such as thermal insulation and improving air tightness – is essential if low-carbon heating systems are to deliver their full environmental and financial benefits.

Approved Document L sets minimum energy performance requirements for new and renovated buildings in England and Wales, covering both thermal efficiency and overall building performance. The Future Homes Standard, which is due to be released later in 2025, further increases expectations. It requires higher levels of insulation, airtightness and low-carbon heating systems. Upgrading home insulation helps to ensure that homes are prepared for tighter regulations, while reducing energy use and minimising the operational load on low-carbon heating systems such as heat pumps.

Heating system upgrades are accelerating

In recent years, there has been a significant increase in the number of households upgrading their domestic heating and hot water systems with heat pumps. Many householders are exploring heat pumps as a way to reduce their energy use and their greenhouse gas emissions. In addition, heat pumps can improve indoor air quality, and some systems can combine both heating and cooling, meaning they can help to keep internal temperatures down in the summer, as well as providing more sustainable heating in the winter and hot water throughout the year.

The UK government is also encouraging uptake of these systems. The Boiler Upgrade Scheme launched in 2022, offering households in England and Wales money towards the cost of a heat pump. The government has also removed VAT on the installation of energy-saving equipment until 2027.

To make it easier for households to install heat pumps, planning permission rules for installing air-source heat pumps in England and Wales were loosened in May 2025 as part of the UK's Warm Homes Plan, Changes involved removing the one-metre boundary rule for external units, increasing the allowable size, permitting two units for detached houses and including air-to-air heat pumps in permitted development rights.

But upgrading the heating system is only part of a bigger picture. To maximise the benefits of a heat pump, the home itself needs to be energy efficient.

A poorly insulated home undermines heating efficiency

Upgrading a home’s heating system with a heat pump can provide financial and environmental benefits, but it’s also important to take a holistic look at the home’s energy efficiency – such as the thermal insulation, doors, windows, ventilation and air tightness.

Mike Vaczi, Technical Director at SOPREMA, explains: “Even with the most efficient heating system, if the property is leaking heat, it’s going to be more energy intensive and expensive to keep the home warm.”

He also warns that insufficient insulation may compromise heating system’s performance. “When a home isn’t adequately insulated, it often means that the heat pump and boiler are oversized or underperforming,” he says.

Insulation is also an important factor in meeting energy efficiency benchmarks such as SAP (Standard Assessment Procedure) and EPC (Energy Performance Certificate) targets. Although SAP is only considered in new builds and major renovation projects, it demonstrates how insulation and heating systems work together to reduce a home’s energy use.

For existing households considering efficiency upgrades, EPC ratings are a more relevant appraisal of a home’s performance. These give each property a letter grade for its energy efficiency, from A (most efficient) to G (least efficient), and are required if a property is being let or sold.

Under the Minimum Energy Efficiency Standards (MEES), which came into effect in April 2020, all domestic properties rented out in the private sector need to have a rating of E or above. The government has also indicated its ambition for all homes to have an EPC rating of C or better by 2035. Ultimately, the goal is for net zero homes – with a combination of energy-efficient heating systems, high levels of thermal efficiency and a decarbonised national grid.


While there are not currently any statutory requirements for improving a home’s energy efficiency rating beyond E, low-carbon retrofits now, such as insulating to a good standard, will improve the property’s energy efficiency, reduce energy bills and potentially increase property values while preventing the need for further upgrades in the future.

Insulation as the foundation of energy efficiency

A fabric-first approach prioritises improving the thermal efficiency of the building envelope before specifying mechanical or electrical heating systems.

This is backed up by PAS 2035 – Retrofitting Dwellings for improved Energy Efficiency – which provides a framework for retrofitting insulation and other energy efficiency measures in existing homes, helping decision-makers take a consistent, whole-house approach.

By enhancing the building’s energy efficiency through methods such as insulating and improving air tightness, it reduces overall heating demand so that the heating and hot water systems that are installed later may be smaller, operate more efficiently and potentially cheaper to run.

Mike points out that a fabric-first approach can also reduce a home’s long-term costs and environmental impact. “Insulating to a high standard now – with thermally efficient materials and high-quality installation and detailing – ensures that a property is future-ready for tighter regulations, avoiding the need for costly or disruptive upgrades later,” he explains.

“Once installed, insulation requires little to no maintenance and has no ongoing running costs. While boilers and heat pumps will need regular maintenance, annual servicing and occasional replacements, thermal insulation continues to perform in the background for the life of the building, keeping the home warmer in winter and more comfortable for occupants, and homeowners don’t have to think about it.”

Thermal insulation and technical guidance: How SOPREMA supports heating system upgrades

SOPREMA manufactures high-performance polyisocyanurate (PIR) and extruded polystyrene (XPS) rigid board insulation for use in walls, roofs and floors in both new-build and retrofit projects. These products are designed to contribute to improvements in U-values and thermal performance, supporting compliance with regulations such as Approved Document L in England and equivalent guidance in Wales, Scotland and Northern Ireland.

In retrofit projects, achieving compliance with frameworks such as PAS 2035 and improving EPC ratings can be complex. A fabric-first approach, starting with insulation, can help to reduce overall heat demand so that heating systems can operate more efficiently. SOPREMA provides product data, technical literature and calculation tools to support specifiers, designers and installers in selecting and detailing insulation measures appropriately for the building type and project requirements.

Technical resources are available on the SOPREMA website, including product datasheets, installation guidance and an online U-value calculator. The SOPREMA technical team is also available to provide project-specific support where required.