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Order Pre 2pm for Delivery How Can You Insulate a Flat Roof with Limited Height?
How Can You Insulate a Flat Roof with Limited Height?
Why Flat Roof Insulation Matters in UK Renovation Projects
How Can You Insulate a Flat Roof with Limited Height? Upgrading insulation is an important requirement when renovating properties in the UK. Under Part L of building regulations, local councils and building control inspectors often require roofs to reach a U value of 0.15. A lower U value indicates better thermal performance, helping to reduce heat loss, cut energy bills, and improve overall comfort.
For many extension or renovation projects, achieving this U value can be challenging, particularly when working with an existing flat roof.
Traditional Warm Roof Systems – The Challenges
Height Constraints in Renovation Projects
The standard method for insulating a flat roof is a warm roof construction, which typically requires around 150 millimetres or more of continuous rigid insulation above the deck. Common rigid insulation boards include brands such as Kingspan and Celotex.
While this method performs well in new builds and is efficient from a labour perspective, renovation projects often face height limitations due to:
Existing roof thresholds and door heights
Parapet wall restrictions
Planning or structural constraints
Drainage fall requirements
Because of these limitations, installing a 150 millimetre PIR board is not always practical or even possible.
A Practical Alternative: The Three Layer SuperQuilt System
Achieving a 0.15 U Value Without Excessive Build Up
Where roof height is restricted, a system that incorporates multifoil insulation products can often be more suitable.
Our recommended solution is the Three Layer SuperQuilt detail, designed to achieve the target U value of 0.15 W per square metre Kelvin while maintaining a slimmer roof build up compared to traditional approaches. This system makes full use of the depth of the roof joists, often without requiring additional ventilation.
Benefits of the Three Layer System
Noticeable cost savings
Ideal for projects with limited height
Strong thermal performance
Supports achieving a U value of 0.15
High performance vapour control layer
SuperQuilt by Soprema is manufactured in the UK and is made up of 19 layers. YBS SuperQuilt also carries a BDA certificate, providing reassurance that the system will be accepted by building control.
Three layers of YBS SuperQuilt are sufficient to achieve a U value of 0.15.
If access below the joists is not available, bespoke systems can be offered where all insulation is fitted between and above the joists.
Nationwide Delivery from Ecohome Insulation
Next Working Day Delivery Across the UK
Multifoils Direct supplies the Three Layer SuperQuilt system as a complete kit, helping installers and homeowners meet performance requirements for flat roof extensions and renovation projects.
The full system is available with nationwide next-working day delivery across the UK. It also includes fixing items such as Thermaseal foil joining tape and a heavy duty staple gun with staples.
Need Help with U Value Documentation?
The team at Multifoils Direct can provide bespoke U value calculations along with condensation reports to submit to your building inspector for approval. If you would like a tailored U value document for your project, please email sales@multifoilsdirect.co.uk
We are also happy to assist with installation questions and general product support. Feel free to get in touch.
