How can Insulate a Flat Roof with restricted height?

Why space-saving on Flat Roofs is so important

Under Part L of building regulations, private and local building controls often require roofs to achieve a U-value of 0.15 W/m²K. The lower the U-value, the better the thermal performance, which results in retaining more heat, reducing heating bills and improved overall comfort.

For large amounts of refurbishment and extesion projects, hitting this U-value can be challenging. 

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, where a thick amount of Rigid Insulation board is fitted as a continuous layer of the joists. Thickness usually is around 140mm - 150mm. Rigid Insulation boards include popular brands like Kingspan and Celotex.
While this method works well in newer builds, and also from a labour perspective, renovation projects often face height restraints due to:

• Existing roof thresholds and door heights

• Parapet wall limitations

• Planning or structural restrictions

• Drainage fall requirements

These retrains results in 150mm PIR Insulation not being a feasible option.

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.

For Flat Roof solutions, we recommend our 3 Layer SuperQuilt detail, designed to achieve the popular U-value of 0.15 W/m²K while maintaining a much slimmer roof build-up compared to traditional methods. Our 3 Layer SuperQuilt detail uses the depth of the roof joists, allowing the multifoils to expand and reflect.

Benefits of the 3 Layer System

• Significant cost saving

• Suitable for height-restricted renovations

• High thermal performance

• Helps meet U-value target of 0.15

• High performance Vapour Control Layer

SuperQuilt by Soprema is BDA certificate, giving peace of mind that the system will be accepted when going through building control. SuperQuilt is a multi-layered foil blanket in 40mm thicknss, consisting of 19 layers.

To achieve the U-value of 0.15, you would require 3 layers of SuperQuilt.

Unable to access under the joists? We can provide bespoke calculations where the multifoil insulation layers is install between and over the joists.

Nationwide Delivery Service from Multifoil-Insulation

Free Nationwide Next Working Day Delivery

Multifoil-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?

Multifoil Insula 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!