How Do You Insulate a Flat Roof with Limited Height?
Why Insulation for Flat Roofs Matters in UK Renovation Projects
Improving insulation is a key requirement when renovating properties in the UK. Under Part L of building regulations, local councils and building control inspectors often require roofs to achieve a U-value of 0.15 W/m²K. A lower U-value means better thermal performance, helping to reduce heat loss, lower energy bills, and improve overall comfort.
For many extension or renovation projects however, achieving this U-value target can often provide challenges, particular when insulating an existing flat roof.
The Challenge with Traditional Warm Roof Systems
Height Restrictions in Renovation Projects
The traditional approach to insulating a flat roof is a warm roof construction, typically requiring around 150mm or more of continuous rigid insulation above the deck. Rigid Insulation boards include popular brands like Kingspan and Celotex.
While this method works well in new builds, and also from a labour perspective, renovation projects often face height restraints due to:
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Existing roof thresholds and door heights
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Parapet wall limitations
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Planning or structural restrictions
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Drainage fall requirements
Because of these constraints, adding a thick PIR board of 150mm is sometimes not practical or even possible.
A Practical Alternative: The 3 Layer SuperQuilt System
Achieving a 0.15 U-Value Without Excessive Build-Up
Where roof height is limited, a system incoprating mulifoil insulation products can often be a better suited system.
Our recommended approach is our 3 Layer SuperQuilt detail, designed to hit the common U-value of 0.15 W/m²K while maintaining a much slimmer roof build-up compared to traditional methods. Our 3 Layer SuperQuitl detail will take advantage of the full depth of the roof joists, often without needing to add any ventilation.
Benefits of the 3 Layer System
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Significant cost saving
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Suitable for height-restricted renovations
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High thermal performance
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Helps meet U-value target of 0.15
- High performance Vapour Control Layer
SuperQuilt by Soprema is UK manufactured and consists of 19 layers. YBS SuperQuilt also holds a BDA certificate, giving peace of mind that the system will be accepted when going through building control.
Three layers of YBS SuperQuilt to achieve a U-value of 0.15.
Unable to access under the joists? We can provide bespoke systems where all the insulation is install between and over the joists.
Nationwide Delivery Service from Ecohome Insulation
Free Nationwide Next Working Day Delivery
Ecohome Insulation offers 3 Layer SuperQuilt system as a kit, supporting installers and homeowners to achieve the required performance on flat roof extensions and renovations.
The full system is available with free nationwide delivery across the UK, and also include fixing items such as Thermaseal Foil Joining Tape and a Heavy Duty Staple Gun inc Staples.
Need support with U-value Documentation?
Our helpful and expert at Ecohome Insulation can provide bespoke U-value calculations alongside Condensation Reports to pass on to your bulding inspector for acceptance. If you would like us to create a bespoke U-value document for your project, please email sales@ecohome-insulation.com
We are also happy to help with installation queries and general product support. Feel free to get in touch!
