New Build Regulations For Insulation In The UK

New build regulations

Building regulations play a vital role in ensuring the safety, sustainability, and structural integrity of properties in the United Kingdom. Complying with up-to-date regulations should always be a top priority, especially when it comes to new-build homes. 

As a result of net zero targets and sustainability initiatives, new build regulations for insulation in the UK aim to improve the energy efficiency of walls, floors, roofs, and other building elements. This results in lower utility bills, reduced carbon emissions, and a healthier living environment.

Let’s examine the latest insulation requirements for new builds in the UK to ensure that your property stays fully compliant with building regulations.

What are the Building Regulations for Insulation for New Properties in the UK?

In the UK, the applicable new build regulations for insulation will vary depending on the following factors:

  • Location of the new build (England, Wales, or Scotland)
  • Type of building (domestic or non-domestic)
  • Application of insulation (floor, walls, or roof)


In England, Approved Document L (Approved Document L: Conservation of Fuel and Power) provides guidance on regulations and standards covering the energy performance of new and existing buildings, including the levels of thermal insulation required.

Meanwhile, Wales adheres to separate standards in Approved Document L, published by the Welsh Government. For Scotland, it’s Section 6 of the Technical Handbook (with guidance for April 2024 already released for new home builders to adhere to relating to insulation and limiting any traditional gas heating system that emits more than a negligible amount of greenhouse gases in new build properties), while Northern Ireland follows Technical Booklet F1.

Each of these approved documents addresses the requirements for new builds in terms of energy efficiency, carbon dioxide emissions, and insulation. They ensure that all newly constructed buildings are cost-effective, environmentally friendly, safe, and comfortable to live in.

Insulation Requirements for New Builds

To limit unwanted heat loss and minimise energy consumption in new dwellings, building regulations provide specific standards for the following:

  • Building fabric 
  • Airtightness
  • Pipework and services


Note that a building’s fabric consists of its floors, walls, roof, windows, doors, and other structural elements that make up the building. The required level of thermal insulation for these building elements is expressed in U-values.

U-values measure the rate of heat loss through a particular building element. When it comes to insulation, a lower U-value is preferable since it represents lower heat transfer and high levels of insulation, meaning your home is better able to hang on to the heat it creates, improving its overall thermal performance.

In England, the Approved Document L provides the target thermal U-values and other insulation-related requirements that new builds must comply with. Below we’ll cover the U-values for England, although you should be aware that other minimum U-values may be expected elsewhere, especially in Scotland, where U-values are usually slightly lower due to the colder weather experienced. For specific information for Scotland new build homes, see their updated for April 2024 Technical Handbook.

For now, the following figures apply predominantly to England, but will be similar across the whole of the UK:

1. Roof Insulation

Did you know that uninsulated buildings lose up to 25% of heat through the roof? Insulating your loft, flat roof, or attic is an effective way to minimise heat loss and reduce energy demand, allowing you to save energy, money, and the environment. 

New build regulations require you to provide thermal insulation to achieve a target U-value of 0.11 for your roof. They don’t stipulate the exact type of insulating material to use, but it must possess sufficient thickness and have good thermal properties.

2. Wall Insulation

Unwanted heat loss also occurs through your home’s walls. Wall insulation is necessary to keep out draughts, prevent damp patches, and maintain a comfortable indoor temperature.

There are three main types of wall insulation in the UK:

  • Cavity wall insulation: Filling the hollow spaces in your home’s cavity walls with blown mineral fibre, polystyrene beads, or any applicable insulating material
  • External solid wall insulation: Involves adding a layer of decorative weather-proof insulating treatment to the outside walls of your home
  • Internal solid wall insulation: The application of thermal material on your property’s inside walls, which can slightly reduce the size of your rooms


According to new build regulations, your walls’ thermal insulation should allow you to reach the target U-value of 0.18 for external walls, including semi-exposed walls. 

3. Floor Insulation

Most homes in the UK have floors made of suspended timber or solid concrete. In either case, insulating the floor of your home will allow you to retain more heat and eliminate draughts coming from gaps in between floorboards.

Generally, you’ll only need to install floor insulation on ground floors or floors above unheated areas, like your garage. New build regulations require insulation that enables you to meet the target U-value for floors, which is 0.13.

4. Continuity of Insulation

Gaps in the insulation in new buildings can have a major impact on heat loss and can cause issues with moisture and mould. New builds should comply with the following measures to avoid gaps and ensure the continuity of insulation:

  • The building designer and installer must inspect drawings to ensure the continuity of the insulation layer
  • An on-site audit of designed details should be performed before elements are concealed
  • Insulation must fit tightly to walls, roofs, floors, and foundations without any air gaps
  • Windows and doors should maintain the thermal integrity of the insulated plane
  • Penetrating elements, such as steel beams and incoming services, should limit disruption to the insulation
  • Insulation must fit tightly around ducts, pipes, and other incoming services


5. Limiting Thermal Bridging

Thermal bridging occurs when part of a building’s wall, roof, or floor loses more heat than its surrounding area. This is usually a result of insulation breaks, building design flaws, or inappropriate choice of material.

Building regulations provide the following measures to limit thermal bridging in new builds:

  • Usage of materials that help to reduce thermal bridges, including insulated plasterboard for timber construction and lightweight blockwork for the inner leaves of cavity walls
  • Continuing insulation across the wall-to-gable and wall-to-eave junctions in roofs
  • Window designs that lessen thermal bridging
  • Detailed wall-to-floor junctions to ensure continuity of the insulation
  • On-site audit of design details and proper assessment of thermal bridges


6. Ensuring Airtightness

An airtight building restricts the inward or outward movement of air by eliminating unintended gaps and cracks in its exterior. Airtightness promotes thermal efficiency and prevents draughts, moisture, pollen, and pollutants from infiltrating the building.

To ensure airtightness, new builds should apply the following measures:

  • Provide drawings reviewed by the designer and installer to identify the air barrier’s position, continuity, and extent
  • Group ducts and cables together to minimise air barrier penetration
  • Keep holes for internal building services that penetrate the air barrier as small as possible
  • Effectively seal structural penetrations for airtightness
  • Tape and seal window and door frames to the appropriate structural openings
  • Ensure optimum air tightness when designing and installing insulation layers


7. Pipework Insulation

To reduce heat loss from hot water storage vessels and heating pipework, new builds are required to insulate all of the following pipework in a new system:

  • Primary circulation pipes that are for heating circuits
  • Primary circulation pipes that are for domestic hot water
  • Pipes connected to storage vessels for hot water
  • Secondary circulation pipework


As for existing systems, any accessible pipes in the dwelling must be insulated when a hot water storage vessel or boiler is replaced.

Building regulations also provide maximum heat loss values and minimum pipework insulation thicknesses that hot water systems should comply with.

Finding the Right Insulation Installer for Your New-Build Home

Insulation is the foundation of an energy-efficient, eco-friendly, and comfortable home. Over the years, new-build insulation has transitioned from being a mere requirement into a healthy and cost-effective choice with long-term benefits.

If you’re looking for a trustworthy insulation installer who understands the standards required for both new and existing buildings, Insulation Advisor is here to help. We’ll connect you with a highly-rated installer in your area so you can get started on insulating your home the right way today.

Click here to get your free insulation quote.

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