Over & Under Joists (Internal & External) Insulation Solutions

Insulating a flat roof over, between and below the joists is the common method chosen for re-roofing existing buildings, extensions and new builds as it provides superior thermal performance for the building. Insulating the roof above and below the joists is known as warm deck insulation as the joists are brought into the insulated envelope of the building.

This over and under joist insulation method also reduces thermal bridging, giving an airtight continuous layer of high-performance insulation and results in a well-insulated attic space. The need for ventilation is also removed*

Insulating your flat roof can be an expensive job, so selecting the right solution is important.

Here at YBS insulation we have specifically designed products that offer high thermal performance, whilst meeting specific performance requirements such as vapour control, etc,

Insulating externally and internally is a quick and easy way to achieve high thermal values that meet building regulations.

The recommended roof insulation for this method of warm roof construction are shown below.

3 & 4 layer insulation solutions

3 Layer Solution

4 Layer Solution

Our 3-layer SuperQuilt solution is all you need to insulate your flat roof extension or new build project.

This quick and easy to install solution offers a high level of thermal performance exceeding building regulations target u-value of 0.18.

Recessing a layer of SuperQuilt over, between and under joists removes the need for a vapour control layer, increases the overall thermal efficiency of the flat roof and increases the internal space available due to its ultra-thin profile.

Using SuperQuilt can significantly reduce the overall impact to head height, when compared to traditional insulation solutions, saving you valuable money, time and space.

Need to meet new build regulations?

Try our 4 layer solution, offering the same great benefits but with higher thermal performance.

Once SuperQuilt has been taped and sealed on all overlaps and perimeter, it also works as a high performing VCL (vapour control layer).

Multiple layers of SuperQuilt can be used to achieve your desired U-Value, for more information speak to our technical support team on 01909 726 025

Description (rafters at 400mm centres)U-Value
SuperQuilt (3 layers)0.16
SuperQuilt (4 layers)0.12
In accordance with BDA Kiwa Agrèment certification(W/m²K)
Description (rafters at 600mm centres)U-Value
SuperQuilt (3 layers)0.15
SuperQuilt (4 layers)0.12
In accordance with BDA Kiwa Agrèment certification(W/m²K)

For optimal visual performance, use the highest available quality, click the Cog icon

* It is always recommended that you speak with one of our technical support team on 01909 726 025, if you are unsure about the ventilation requirements of your application.

SuperQuilt 2 Layer Insulation Solution & Traditional Insulation Between Joists

Description (rafters at 400mm centres)U-Value
SuperQuilt (2 layers) 0.22
SuperQuilt (2 layers) and 20mm PIR (0.022 W/mK)0.18
SuperQuilt (2 layers) and 90mm PIR (0.022 W/mK)0.13
In accordance with BDA Kiwa Agrèment certification(W/m²K)
Description (rafters at 600mm centres)U-Value
SuperQuilt (2 layers) 0.22
SuperQuilt (2 layers) and 20mm PIR (0.022 W/mK)0.18
SuperQuilt (2 layers) and 70mm PIR (0.022 W/mK)0.13
In accordance with BDA Kiwa Agrèment certification(W/m²K)

Our 2-layer solution offers a great option for flat roof refurbishments, loft conversion, extensions, or new build projects where there is access to the external and internal of the roof.

This quick and easy to install solution offers a high level of thermal performance meeting building regulations target u-value of 0.18.

Need to meet new build regulations of 0.13?

Simply increase the thickness or performance of the traditional insulation used between the joists.

SuperQuilt can be pulled taut over or under the joists, followed by a minimum 25mm timber batten, this option is good for projects where there is limited space between the joists, or the profile height or internal head height of the roof has no restrictions.

For applications where there are large joists with no restrictions, SuperQuilt can be recessed down between the joists. This detail keeps the overall roof profile height or impact to the internal head height down to a minimum, by allowing the SuperQuilt to expand between the joists.

Using SuperQuilt can significantly reduce the overall impact to head height, when compared to traditional insulation solutions, saving you valuable money, time and space.

Once SuperQuilt has been taped and sealed on all overlaps and perimeter, it also works as a high performing VCL (vapour control layer).

For optimal visual performance, use the highest available quality, click the Cog icon

* It is always recommended that you speak with one of our technical support team on 01909 726 025, if you are unsure about the ventilation requirements of your application.

Product Guides

YBS SuperQuilt

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Certification

YBS Insulation products are manufactured to the highest quality and certified to industry standards.

YBS Insulation Product Information

Product - SuperQuilt - See more

SuperQuilt is one of the UK’s leading multifoil insulations. This flexible, easy to install, multilayer insulation offers tremendous thermal benefits. The benefit of multifoil insulation is that it is suitable for a range of applications from roof insulation, floor insulation and wall insulation and due to the slim depth, you can save valuable space on your installation. The unique composition of the product effectively deals with all forms of energy transfer.

This product is suitable for roofs, walls, floors and offers the following major benefits –

  • Cost saving Solution
  • Effective 2 in 1 insulation and vapour control membrane
  • Reduces Construction Depth
  • Reduces Risk of Condensation
  • Non degradable maintaining thermal performance and product integrity

SuperQuilt has been independently tested and certified to the latest Industry Standards, including BDA Kiwa certificate of Agrément, Building Control Compliance (LABC registered detail) and NHBC Acceptance.

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