How to achieve 0.18 U-value – Timber Frame Walls

How to achieve 0.18 U-value – Timber Frame Walls

Looking to insulate a new dormer wall, or timber frame extension? If the project is requiring a sign-off from building control, it is likely you have been asked to achieve a 0.18 U-value. Going through building control can be difficult when achieving low U-values, especially when facing cost and space restraints.

What is a U-value?

A U-value is a measurement of heat loss through a certain area. A U-value calculates and takes account of all the thermal resistances (R-values) in the structure. For example, in a timber frame structure, you generally have common layers such as OSB and Timber Studs. Hitting specific U-value calculations are a certain aspect when going through building control.

Target U-values for 2024

Approved Document Part L has been updated in relation to U-values, heat gain and heat loss. The new target U-values came into play June 2022. More information on Part L can be found at the following link on the UK government website – See Data Source.

New for 2023 – U-value requirements for existing dwellings

Application Current U-value
Roof (Flat Roofs & Pitched Roofs) 0.15
Wall 0.18
Floor 0.18

Types of Timber Frame Walls

Hitting the U-value target of 0.18 relates to details such as Timber Frames, Dormer Walls, Dormer Cheeks, Dwarf Walls. You will find the usual recommended minimum stud depth is 69mm. If deeper studs are used, you can find achieving your U-value may become easier or cheaper. For clarification on the best detail, feel free to contact us, or request a U-value.

Benefits of Timber Frame Construction

Building a timber frame building are proven to provide a speedier installation compared to standard masonry. Timber is a completely renewable source which has the lowest CO2 cost of all materials. Timber stud walls also have improved flexibility, assisting in meeting structural and aesthetic requirements.

Recommended Product – YBS SuperQuilt

Multifoils Directs recommended product for dormer and timber frame walls is YBS SuperQuilt. SuperQuilt is a 19 layer, 40mm certified roofs and many types of walls. It’s a thin, flexible and high performing multifoil insulation, with many benefits compared to traditional rigid board insulation.

Below are a few of SuperQuilt’s Key Benefits;

  • Fully certified by BDA Kiwa
  • Build-in Vapour Control Layer
  • UK Manufactured – YBS Insulation
  • Compresses to just 7mm
  • 98% Reflective True Aluminium Outer Layers
  • Made from 83% recycled materials

Installation Options to achieve 0.18 U-value

Below are our recommended details to achieve this popular U-value figure;

  • Option A – Standard Breather Membrane, 50mm PIR Insulation in Stud, 1 Layer SuperQuilt Internal of Stud, Batten, Plasterboard
  • Option B – BreatherFoil FR Reflective Membrane, 1st SuperQuilt Recessed in Stud, 2nd SuperQuilt Internal of Stud, Batten, Plasterboard
  • Option C – Standard Breather Membrane, 100mm Rockwool in Stud, 1 Later SuperQuilt Internal of Stud, Batten, Plasterboard (Min 125mm Stud)
0.18 Timber Frame Detail

2 Layers of SuperQuilt & BreatherFoil.

Require approval from Building Control?

It is often requested by your private building control, or local council for proof that U-value meets the requirements. You can download all the mentioned calculations from our Online U-value Calculator. After a few simple steps and questions, our website will email over this bespoke U-value calculation in a downloadable PDF format. Once the bespoke calculation has been received, you can simply forward this over to your building inspector for acceptance.

We also have many cost and space effective methods for Solid Walls!

Looking to insulate a roof or floor? Multifoils-Direct have over 1,000 bespoke U-value calculations for a range of all applications. So if you’re looking to build a new home, renovate a property, or add a dormer extension, there is always a solution for you!

Struggling to find the correct detail for your project? If so, feel free to fill in our Request a U-value Form. Once you have filled in our form, our technical team will email a bespoke U-value calculation & quote at the lowest trade prices.

Delivery Schedule

Multifoil’s Direct offer SuperQuilt at the lowest trade prices, with next-working day delivery!

You can purchase as individual rolls, or as fully packaged Trade Pallet Deals.

See below links to order both online with next-working day delivery;

SuperQuilt Loose Rolls – Click Here!
SuperQuilt Trade Pallet – Click Here!
BreatherFoil FR Loose Rolls – Click Here!


All build-ups and suggestions are provided in good faith. Our recommend details should be double checked with building control before committing to a purchase. The U-value table is a guide, and your desired target U-value is to be advised from your building inspector. Please check the calculations for correct air-gaps and battens. Multifoils-Direct cannot be held responsible for any losses financially or physically from advice provided on this webpage