Under Joist (Internal) Insulation Solutions

INSULATING A FLAT ROOF BELOW & BETWEEN JOISTS.

Insulating a flat roof between and below the joists is a very common roof insulation choice, particularly for retrofit, refurbishment or conversion projects.

This method of installing roof insulation allows you to maximise the headroom by using a thinner layer of insulation beneath the Joists, whilst achieving U-Values which will ensure you comply with Building Regulations and have a roof space which is comfortable for its occupants.

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

SuperQuilt Under Joists & Traditional Insulation Between Joists

Our internal Flat roof insulation solution is a quick and efficient method of insulating your flat roof project.

Installing a layer of SuperQuilt internally 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.

SuperQuilt can be used on its own or with traditional insulation such as PIR or mineral wool between the joists.

Alternatively, 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

Using SuperQuilt can significantly reduce the overall impact to head height, when compared to traditional insulation solution, 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).

Description (rafters at 400mm centres)U-Value
SuperQuilt 0.44
SuperQuilt and 85mm PIR (0.022 W/mK)0.18
SuperQuilt and 140mm Glasswool (0.040 W/mK)0.18
SuperQuilt and 150mm PIR (0.022 W/mk)0.13
In accordance with BDA Kiwa Agrèment certification(W/m²K)
Description (rafters at 600mm centres)U-Value
SuperQuilt 0.44
SuperQuilt and 85mm PIR (0.022 W/mK)0.18
SuperQuilt and 140mm Glasswool (0.040 W/mK) or 120mm Glasswool (0.040 W/mK)0.18
SuperQuilt and 140mm PIR (0.022 W/mk)0.13
In accordance with BDA Kiwa Agrèment certification(W/m²K)

2 Layers Of SuperQuilt Under Joists & Insulated Plasterboard

Our 2 layer internal flat roof insulation solution is a quick and efficient method of insulating your flat roof.

Properties with smaller joist depth can be an issue when specifying traditional insulation like PIR & Mineral wool due to the high thickness of insulation required.

Recessing a layer of SuperQuilt between the joists and a layer of SuperQuilt internally 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.

SuperQuilt can be used on its own or in conjunction with an insulated plasterboard, giving you a hassle free installation, saving you valuable money, time and space. For more information speak to our technical support team on 01909 726 025

For projects with larger joists, traditional insulation like PIR and Mineral Wool can be used between joists, removing the need for an insulated plasterboard.

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

Description (rafters at 400mm centres)U-Value
SuperQuilt (2 layers) 0.25
SuperQuilt (2 layers) with 53mm Insulated Plasterboard (PIR) (1.850 m²k/w)0.17
SuperQuilt (2 layers) and 30mm PIR (0.022 W/mK)0.18
SuperQuilt (2 layers) with 80mm Insulated Plasterboard (Phenolic) (3.560 m²k/w)0.13
SuperQuilt (2 layers) and 100mm 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) 0.25
SuperQuilt (2 layers) with 53mm Insulated Plasterboard (PIR) (1.850 m²k/w)0.17
SuperQuilt (2 layers) and 25mm PIR (0.022 W/mK)0.18
SuperQuilt (2 layers) with 80mm Insulated Plasterboard (Phenolic) (3.560 m²k/w)0.13
SuperQuilt (2 layers) and 100mm PIR (0.022 W/mK)0.13
In accordance with BDA Kiwa Agrèment certification(W/m²K)

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YBS SuperQuilt

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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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