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New Build Cavity Wall Insulation Regulations in 2023

Cavity wall constructions have long been a favoured method for building homes and other structures throughout Britain. However, with the recent revisions to the building regulations, there's now an increased emphasis on enhancing the insulation levels of these walls.


This change can significantly increase the thickness of the insulation, which can consequently affect the overall width of the wall construction. This alteration could reduce the available interior space of a building.


In this article, we'll delve into the updated cavity wall insulation building regulations for both domestic and non-domestic structures.


Additionally, we'll explore strategies for employing highly efficient insulation materials that allow for a narrower cavity, ensuring you don't compromise on internal living space.


New Build Cavity Wall Insulation Regulations in 2023

Understanding the Required U-value for New Cavity Walls According to Building Regulations


When determining the insulation thickness required for cavity walls, a good initial reference is the notional building specification relevant to your country. These specifications provide detailed guidance that helps ensure compliance with the energy efficiency benchmarks outlined in the Building Regulations and Standards.


These guidelines also define essential metrics, such as carbon emissions and energy demand, which new structures must satisfy. To ascertain the exact benchmarks for a specific project, these notional building specifications are utilized on a hypothetical model building that mirrors the size and layout of the planned construction. The metrics are then drawn from the outcomes of this model.


While project teams can deviate from the specifications, they must still meet all mandatory metrics. The provided values are crucial as they clearly show the building's performance expectations.

In light of the recent emphasis on building regs wall insulation thickness, it's vital to ensure that these U-values align with the latest standards, enabling structures to be energy-efficient and environmentally friendly.

Area weighted U-values (W/m²K)

Domestic

Non-Domestic

Side-lit and unlit (such as offices and schools)

Side-lit and unlit (with cooling)

Top-lit (such as warehouses)

England - ADL 2021

0.18

0.18

0.18

0.26

Wales - ADL 2022

0.13

0.22

0.26

0.26

Scotland - TH6 2022

0.15

0.15

0.15

The Minimum U-value According To New Build Cavity Wall Insulation Regulations


The cavity wall regulations specify baseline U-values as permissible 'area-weighted' measures for each structural component, which all new constructions must either meet or surpass. It's essential to understand that these figures serve as maximum allowable limits rather than objectives.


Simply put, for your external walls, the U-value should be below 0.30 (as per L1A 2013). If the U-value of your new residence exceeds 0.30, it won't meet the building regulations standards.


Relying solely on these values to design external walls might make it challenging to ensure obedience. Additionally, while particular sections of the structural element might have less efficient U-values, it's acceptable as long as the accumulative performance of that element balances out the differences.

Area weighted U-values (W/m2K)

Domestic

Non-Domestic

England – ADL 2021

0.26

0.26

Wales – ADL 2022

0.18 (dwelling house), 0.21 (flats and apartments).

0.26

Scotland – TH6 2022

0.17

0.21

What's The Latest Update?


The latest June 2022-2023 update to new cavity wall insulation building regulations for new constructions is crucial knowledge for builders and homeowners alike! The Department for Levelling Up, Housing, and Communities (DLUHC) has made a significant announcement: From June 2022, new build homes in England are mandated to achieve a 30% reduction in carbon emissions.


While this directive doesn't focus exclusively on cavity wall insulation, learning its implications is vital. To meet the DLUHC's compulsory target, one practical approach is to reduce heat loss through your cavity walls.


You might be wondering: if my construction already satisfies the prescribed maximum U-value for external walls, what more can be done?


The answer lies in carefully selecting insulation and building materials, which can facilitate even better U-values. It might astonish you, but surpassing these standards is more achievable than you'd imagine.


How Thick Should Your Cavity Wall Insulation Be?


The required building regs wall insulation thickness is not a one-size-fits-all answer. It's influenced by various factors, with the thermal conductivity of the insulation material and other building components being the most crucial.


Thermal conductivity is a measure of how effectively a material can conduct heat. Materials with a lower thermal conductivity are superior insulators, preventing heat loss more efficiently. This means you can often use a thinner layer of such materials to achieve the U-value you're targeting.


For instance, Kooltherm K106 and K108 have a thermal conductivity of just 0.019 W/mK. This value is considerably lower than other popular insulation choices like mineral wool. Due to their superior thermal performance, Kooltherm products can often reduce construction depths.


Comparison of Insulation Materials for a Typical Cavity Wall Construction:

Construction

Insulation and residual cavity

Blockwork type and wall U-value (W/m2K)

Aerated (0.11)

Lightweight (0.15)

Medium (0.51)

Dense (1.13)

102.5 mm brick outer leaf

100 mm blockwork

12.5 mm skimmed plasterboard on dabs


1. 90 mm Kooltherm K106 with 10 mm cavity

0.16

0.17

0.18

0.18

2. 115 mm Kooltherm K106 with 10 mm cavity

0.13

0.14

0.14

0.15

3. 175 mm mineral wool (0.037 W/mK) fully filling cavity

0.18

0.20

4. 75 mm Kooltherm K108 with 50 mm cavity

0.17

0.18

0.19

0.19

5. 100 mm Kooltherm K108 with 50 mm cavity

0.14

0.15

0.16

0.16

Final Thoughts


Navigating the nuances of building regulations and ensuring optimal insulation can be tiring. However, understanding the significance of cavity wall insulation building regulations, especially in light of recent updates, is paramount.


The right choice in insulation, such as materials with lower thermal conductivity, can not only help achieve the required U-values but can also potentially reduce the overall construction depth.


As we move towards a more energy-efficient future, being well-informed and making strategic choices in insulation can make all the difference in ensuring that our homes and buildings are comfortable and compliant.


Read more: Do I Need to Tell My Electricity Supplier I Have Solar Panels?

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