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Insulation and Building Codes: What You Need to Know in 2024

As we approach 2024, staying updated with the evolving building codes related to insulation is crucial for homeowners, contractors, and developers alike. Regulation changes can impact new construction and renovations, affecting project timelines, material choices, and installation methods. This blog delves into the key updates to insulation and building codes for 2024 and how they influence insulation practices across the UK.

What are building codes?

Building codes are essential frameworks that govern building design, construction, and renovation to meet safety, health, and environmental standards. They are dynamic, evolving with technological advancements, materials science, and environmental priorities.

The primary aim is to protect public health, safety, and general welfare by constructing and occupying buildings and structures. This includes ensuring structural integrity, safe electrical wiring, and adequate means of egress. Codes help reduce energy consumption by setting minimum standards for the thermal performance of buildings, including walls, roofs, windows, and doors. Regulations may also include measures to reduce the environmental impact of building construction and operation, encouraging sustainable practices and materials.

Compliance and enforcement

While national codes provide a baseline, local governments often adapt these codes based on regional climate, environmental concerns, and urban planning needs. Building inspections are conducted at various stages of construction to ensure compliance with codes. Permits are required before construction can commence, ensuring plans are reviewed and approved by local building authorities. Insulation products and installation methods may need to meet specific standards and certifications to be code-compliant. This ensures they have been tested for performance and safety under prescribed conditions.

Non-compliance can lead to fines, legal action, and the requirement to redo work, resulting in increased costs and project delays. Improperly installed or substandard insulation can lead to risks such as poor indoor air quality, fire hazards, and inadequate thermal protection.

Insulation and building codes

These are specified using R-values (resistance to heat flow) or U-values (heat transfer rate). Codes dictate minimum R-values for different building parts, ensuring effective thermal insulation. Building codes often require airtightness to reduce energy loss and prevent moisture-related issues, which are critical in insulation systems. Requirements on the placement and type of vapour barriers to manage condensation and prevent moisture ingress can degrade insulation performance and lead to structural issues.

Thermal Performance Standards (R-Values and U-Values)
  • Walls: The typical U-value target for walls in new dwellings is around 0.18 W/m²K, though this can vary slightly depending on the specific construction method and materials used.
  • Roofs: The U-value of roofs should not exceed 0.13 W/m²K for pitched roofs with insulation at the ceiling level and 0.18 W/m²K for flat or pitched roofs with insulation at the rafter level.
  • Floors: Ground floors should generally achieve a U-value of no more than 0.18 W/m²K.
  • Windows, Doors, and Skylights: The maximum U-value for these elements should be 1.6 W/m²K for windows and skylights and 1.8 W/m²K for doors.

Thermal bridging refers to areas of the building envelope that have a higher thermal transmittance than the surrounding materials. This is typically at junctions and where the building fabric is penetrated by other elements. The regulations specify that thermal bridging should be minimised and calculated with a psi-value, which should be included in the overall building CO2 emission calculations. Typical y-values (total heat loss parameter) used for assessing the overall heat loss from thermal bridges in new buildings should not exceed 0.08 W/m²K.

For existing buildings undergoing renovation, if more than 25% of the surface of an individual thermal element is renovated, it must be upgraded to meet minimum thermal standards, typically requiring that walls achieve a U-value of 0.30 W/m²K or better.


The building regulations require an air permeability of no more than 5 m³/(h·m²) at 50 Pa (Pascal pressure unit) in new homes. This standard is tested by a pressure test on completion of the building.

Air-Tightness-Testing for insulation and building codes

Vapour control

Vapour control requirements are designed to manage condensation risk within the building envelope. The specifics can vary by construction type and climatic region. Still, typically, a vapour control layer (VCL) should be included on the warm side of the insulation layer to prevent moisture from penetrating the insulation. It could condense and cause dampness or mould issues.

damp proof course
A DPC in place in a cavity wall
Future-proofing and higher standards

With a trend towards more stringent regulations, future revisions to Part L are expected to push these values even lower as part of the UK’s strategy to achieve net-zero carbon emissions by 2050. This involves the “Future Homes Standard”, expected to come into effect by 2025, aiming for a 75-80% reduction in carbon emissions compared to current levels.

How do you ensure that insulation satisfies building codes?

Understand local Building Codes

Start by familiarising yourself with the local and national building codes related to insulation, such as thermal resistance (R-values), fire safety, and environmental standards. These codes vary by region and the type of building (residential vs. commercial).

Select appropriate insulation materials

Choose insulation materials that meet or exceed the specified R-values in the building codes. Consider other factors like fire resistance, moisture resistance, and environmental impact. Products usually come with datasheets that detail their performance specifications.

Consult professionals

Engage with architects, building inspectors, or energy assessors early in the planning stage. These professionals can guide compliant materials and design considerations to meet or exceed the necessary standards.

Design considerations

Incorporate details such as thermal bridging, air tightness, and vapour barriers into the design. These factors are crucial for meeting building codes related to energy efficiency and moisture management.

Professional installation

Use qualified contractors to install insulation. Proper installation is crucial to achieving energy efficiency and complying with building codes. Incorrect installation can reduce performance, compliance issues, and potential structural problems.

Inspection and testing

Once the insulation is installed, it should be inspected by a certified building inspector. In many cases, this will involve air tightness testing and thermal imaging to identify any gaps or areas of thermal bridging.

Moisture testing of existing walls
Moisture testing of existing walls
Documentation and certification

Maintain all documentation related to the insulation materials used, including purchase receipts, product datasheets, and compliance certificates. These documents may be required for building inspections or future renovations.

Stay updated on code changes

Building codes can change, so staying informed about updates or new regulations is important. Subscribing to updates from building regulation bodies or attending seminars can be beneficial.

Retrofit compliance

For retrofit projects, assess the existing insulation and structure to ensure that any additional insulation complies with current codes. This often involves more complex calculations to balance new with old and achieve compliance.

Energy Performance Certification:

Obtaining an Energy Performance Certificate (EPC) can affirm that a building meets the required standards for new builds or major renovations. The EPC assesses a building’s energy efficiency and is often a necessary compliance document.


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