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Rigid PIR Insulation boards above between and below rafters at pitch roof level

Application - Loft floor / above ceiling / below ceiling

including between and above + between joists, and below ceiling

Insulating at ceiling or loft floor level generally occurs in a cold roof environment, in which case the most common, best value, and easiest to install standard solution is to uses a Glass Mineral Wool Loft Roll.

In cases where noise is a problem, Acoustic Partition Roll is favoured, as it provides both thermal and acoustic insulation properties.

Complications arise when occasional use is made of the loft for storage, for example. In this case partial or complete boarding of the floor of the roof void is desired. One way to resolve this all-to-common problem is to use mineral wool slabs between the ceiling joists, then fit battens perpendicular to the joists, and insulate between these battens and applying chipboard flooring on top.

Insulation Installation Locations

Cold roof joist level applications include insulation ...

Between Ceiling Joists -

It is almost certain that insulating between the joists alone will not be sufficient, as a depth of 300mm of Loft Roll 44, is the recommended minimum to achieve a U Value of 0.18, as required by building control.

It should be understood that the flossy formation of loft roll must be maintained to ensure its effectiveness. Squashing the air out of loft roll will dramatically reduce its thermal value.

Between and Above Joists -

The most common build-up of Loft Roll insulation is fit 100mm between the joists then placing 200mm (or 2 x 100mm) above the rafters perpendicular to each other.

Soundproofing can be enhanced by fitting Mineral wool slabs in place of, or in conjunction with Loft Roll or Acoustic Partition Roll.

Reflective foils and rigid insulation with solid aluminium facings are not recommended in this location, due to their potential to promote condensation.

Below Ceilings

Mechanically fixed insulated plasterboard is recommended when other alternatives do not exist.

Ceiling Level Build-up / Insulation Types / Combinations + Examples

Loft space

Rigid / semi rigid insulation

Glass / rock mineral insulation

Foil-backed plasterboard /Insulated Plasterboard

Loft space

Glass / rock mineral insulation

Plasterboard / Insulated Plasterboard

At the most basic level of insulation, the variety of options is very limited

Ceiling Level Insulation Products

Listed below are links to the most popular application specific product brands associated with Ceiling Level insulation projects

Rigid Insulation Boards

Semi Rigid Insulation

Multi-foil & Breather Foils

Breather & Foil Membranes

Plasterboards & Thermal Laminates

Kingspan K3

Isover SpaceSaver


Tyvek Housewrap

Celotex PL4000

Kingspan TR27

Knauf Loft Roll 40 + 44


Tyvek Supro / Supro Plus

Gyproc Plasterboard


Isover Acoustic Roll



Gyproc Thermaline


Knauf Acoustic Roll


Kingspan K18


Knauf Earthwool Slabs


Knauf Plasterboard

Rockwool Flexi Slabs

Knauf Thermal Laminate

Knauf OmniFit Slabs

Rockwool RW Slabs

Our Contact Details

Sales Office only:
39 Normandy Road, Worthing, West Sussex, BN14 7DX

Telephone: 0333 9000 989

Facsimile: 0333 7000 797


Web presence:

Web Sites

Minimum order £175.00 ex-VAT. Delivery vehicle sizes - flexible

Minimum order £500.00 ex-VAT. Delivery vehicles size - 28 tons+

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