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Pitched Roof Insulation

Pitched roofs are very popular in many types of commercial and public buildings and can be constructed in two ways – with a ceiling and without a ceiling, depending on the building specification and design. Some designs do not include ceiling and the height of the pitched roof is used to create light, attractive, interiors. Some specifications require the roof void to be utilised as an additional room. When converting your attic into a room, insulation is placed in between the rafters to create a worm roof.

Various products can be used for pitched roof insulation: semi-rigid insulation boards such as expanded polystyrene board, extruded polystyrene board, glass fibre batts, mineral fibre batts, urethane foam board or phenolic (fireproof) foam boards. If a first layer of insulation is placed between rafters, a second, thin layer is applied to the underside of the rafters to avoid thermal bridging. Glass fibre quilt and mineral fibre quilt can also be used. A vapour check should be installed on the warm side of the insulation and ventilation above. These materials can be held in place by a plaster lining board which also provides the necessary fire protection.

Methods used for insulation will solely depend on the design and building specification.

Following choices are available:

Pitched roof with unutilised roof void insulated at ceiling level

Insulation placed at ceiling level creates a cold roof space; and overall is the lowest cost option for insulating a roof due to a low quantity of insulation material needed. High levels of thermal insulation can be achieved because there is virtually no restriction on the thickness of insulation that can be installed. There are two options when insulating at ceiling level to provide sufficient ventilation of the roof and eliminate moisture condensation; insulating to achieve:

  • Cold ventilated roof:
  • Cold ‘breathing' roof:

Cold ventilated roof insulated at ceiling level contains no vapour control layer; instead, water vapour enters loft through gaps and cracks in ceiling and by diffusion through ceiling plaster. Impermeable bituminous felt underlay placed underneath tiles and slates traps moisture in loft. To eliminate condensation, ventilation trays are created at the eaves of pitched roof to provide clear air path above insulation. Air continuously enters loft through the ventilation trays and leaves through the ridge gap on top of the roof providing cross ventilation to eliminate vapour and defuse moisture, leaving the loft space cold, draughty and dusty.

In a more modern cold ‘breathing’ roof insulated at ceiling level, vapour control layer is placed underneath insulation to reduce vapour entering the loft. Ventilation space is created by counter battens which allow air to circulate underneath tiles and slates providing continuous diffusion of moisture leaving the loft space clean, dry and drought free. It is recommended to use breathing roof construction for all pitched roofs.

Utilised pitched roof void insulated between rafters

Several methods are used to insulate utilised roof void depending on specification. Following choices can be used:

  • warm ‘breathing’ roof insulated between rafters,
  • warm ‘breathing’ roof insulated above and between rafters,
  • warm’ breathing' roof with vapour permeable underlay as tiling underlay
  • warm ventilated roof

In a warm ‘breathing’ roof vapour control layer must be used to underside of insulation to prevent moisture condensation. In a warm ventilated roof it is essential to provide 50mm ventilated airspace between the insulation and the tiling underlay to provide constant diffusion of vapour. If rafter depth is insufficient to accommodate the required thickness of insulation and the 50mm ventilated airspace, an insulated dry lining is recommended to minimise thermal bridging. Ventilation openings should also be provided. At the eaves, ventilation openings should be 25mm continuous gap and at the ridge - 5mm continuous gap on each side of the ridge. A vapour control layer also must be applied to the warm side of the insulation.

Pitched roof with no ceiling insulated between rafters

Insulating this type of roof is a complex task and can be designed in several ways depending on specification:

  • Hybrid pitched roof with a single layer insulation between rafters
  • Hybrid pitched roof twin insulated; between and below rafters

Insulationshop.co offers a wide range of pitched roof insulation from manufacturers Xtratherm, Celotex, Knauf, Kay Metzeler, Cellecta and more. For more information about particular products please see product description.

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20mm Celotex TB4000 PIR Insulation Board - TB4020
Guide Price
Brand: Celotex Model and Size: 1200x2400mm - 2.88m2
Delivery Time: 1 - 5 working days
Celotex TB4020 is targeted at cut-to-fit applications between rafters or joists and enables users to achieve lower U-values with a single layer of insulation than has previously been possible. It is also appropriate for use in floors and walls. With low emissivity foil facings, TB4020 is manufa..
Guide Price: £23.48
£28.18 inc VAT
150mm Rockwool Roll Loft Insulation
Guide Price
Brand: Rockwool Model and Size: 3650x1200mm - 4.38m2
Delivery Time: 3 - 5 days
150mm Rockwool Roll Loft Insulation is a multi-functional medium-density insulation roll, especially designed for improving thermal performance in roofs and lofts, and acoustic performance and sound reduction in suspended ceilings. It can be used in number of different applications in commercial, in..
Guide Price: £77.61
£93.13 inc VAT
25mm Celotex FR5000 Fire Resistant PIR Insulation Board (pack of 16)
Guide Price
Brand: Celotex Model and Size: 1200x2400mm - 46.08m2
Delivery Time: Out Of Stock
Celotex FR5025 is one of the available dimensions of the Celotex FR5000 PIR insulation boards made from polyisocyanurate rigid core and faced on both side with low emissivity aluminum foils for improved thermal performance. The product is applicable to different types of constructions incl..
Brand: TLX Insulation Model and Size: 1.2m x 10m - 12m2
Delivery Time: 2 - 3 days
30mm TLX Silver Multi-foil is an insulation material comprising outer layers of coated metallised film, laminated to a non-woven polypropylene fabric enclosing the core and welded along both long edges. The core of the products consists of five layers of polyester fibre wadding separated by four met..
£99.89
£119.87 inc VAT
Brand: IPP Model and Size: 1.2m x 10m (12m2)
Delivery Time: 2 - 3 days
30mm Alumaflex Multifoil insulation is a sophisticated multi layer radiant barrier of low emissivity. This product comprises 14 layers where the outer layer is a PET (polyethylene terephthalate) fused to a PE (polyethylene) bubble layer which is then fused to a non-woven polypropylene backing. The c..
£92.45
£110.94 inc VAT
Brand: Kingspan Model and Size: K7 2400x1200 - 34.56m2
Delivery Time: 3 - 5 days
25mm Kingspan Kooltherm K7 Pitched Roof Board is the rafter/joist level insulation comprising a premium performance rigid thermoset phenolic insulation core faced on both sides with a low emissivity composite foil facing. This reflective, low emissivity surface improves the thermal resista..
£392.63
£471.16 inc VAT
25mm Rocksilk RS45 Universal Insulation Slab Knauf (pack of 20)
Guide Price
Brand: Knauf Model and Size: 1200x600 - 14.4m2
Delivery Time: 2 - 3 days
25mm Rocksilk RS45 Universal Slabs are rock mineral wool slabs, available in a range of densities and designed for use in multiple thermal and acoustic applications where density is critical. The standard product is supplied unfaced, but slabs can also be manufactured with a factory applied foi..
Guide Price: £41.63
£49.96 inc VAT
50mm Rocksilk RS60 Universal Insulation Slab Knauf (pack of 9)
Guide Price
Brand: Knauf Model and Size: 1200x600 - 6.48m2
Delivery Time: 1 - 2 days
50mm Rocksilk RS60 Universal Slabs are rock mineral wool slabs, available in a range of densities and designed for use in multiple thermal and acoustic applications where density is critical. The standard product is supplied unfaced, but slabs can also be manufactured with a factory applie..
Guide Price: £41.63
£49.96 inc VAT
50mm Rocksilk RS100 Universal Insulation Slab Knauf (pack of 6)
Guide Price
Brand: Knauf Model and Size: 1200x600 - 4.32m2
Delivery Time: 2 - 3 days
50mm Rocksilk RS100 Universal Slabs are rock mineral wool slabs, available in a range of densities and designed for use in multiple thermal and acoustic applications where density is critical. The standard product is supplied unfaced, but slabs can also be manufactured with a factory appli..
Guide Price: £35.43
£42.52 inc VAT
Brand: Knauf Model and Size: 1200x600 - 8.64m2
Delivery Time: 2 - 3 days
50mm Earthwool Flexible is a non-combustible, inorganic rock mineral wool slab, used for thermal and acoustic insulation and specifically designed for installation by friction fitting. Earthwool Flexible is odourless, non-hygroscopic, rot proof, does not sustain vermin and will not encourage th..
£45.31
£54.37 inc VAT
Brand: Rockwool Model and Size: 1200x600mm - 8.64m2
Delivery Time: 1 - 2 days
50mm x1200mm x 600mm Rockwool Flexi Insulation Slab is a unique semi-rigid thermal and acoustic insulation product made from volcanic rock. It has a flexible edge, specifically developed using patented technology for a fast and easy, perfect friction fit between timber and metal frame syst..
£42.50
£51.00 inc VAT
5 (11e 0s)
Brand: Low-E Model and Size: 1.25m x 4m - 5m2 - Free Delivery
Delivery Time: 2 - 3 days
5m2 Low-E EZY-Seal Reflective Foil Insulation Roll gives a superior air infiltration barrier that reduces draughts and uncontrolled air movement and also increases thermal performance by blocking up to 97% of radiant heat. It is also a vapour control layer. Low-E EZY-Seal Reflective Foil I..
£45.54
£54.65 inc VAT
Brand: Low-E Model and Size: 65mm x 45m - Free Delivery
Delivery Time: 2 - 3 days
Low-E Seam Tape is a pure aluminium foil tape and has a Class 1 Fire Rating. This tape has a reinforced scrim mesh under the surface of the tape and increases its tensile strength. This tape is manufactured using the highest quality foil and high strength adhesive. Once applied, it will not de-lamin..
£28.76
£34.51 inc VAT
25mm Yelofoam X2i Cellecta
Guide Price
Brand: Cellecta Model and Size: 2500x600mm - 1.5m2
Delivery Time: 2 - 4 days
25mm Cellecta Yelofoam is made of extruded polystyrene (XPS) foam blown with a mix of HFA & CO2 gases, containing a yellow pigment, flame retardant additive and nucleating agent. Cellecta insulation products are manufactured to the highest possible specification. Ex All product’s’ physical prope..
Guide Price: £17.72
£21.26 inc VAT
Brand: Kingspan Model and Size: TP10 1200x2400
Delivery Time: 3 - 4 days
20mm Kingspan Thermapitch TP10 is the rafter level insulation comprising of a high performance rigid thermoset insulation core faced on both sides with a low emissivity composite foil facing. The product is manufactured with a blowing agent that has zero Ozone Depletion Potential..
£35.42
£42.50 inc VAT
25mm Xtratherm Safe-R SR/PR Phenolic Insulation Board (pack of 12)
Guide Price
Brand: Xtratherm Model and Size: 2400x1200 - 34.56m2
Delivery Time: 2 - 3 days
25mm Xtratherm Safe-R SR/PR Phenolic foam is a superior performance rigid insulation with enhanced fire performance, consisting of a Class O phenolic foam core with negligible smoke obscuration. Safe-R is faced with low emissivity aluminium facings both sides, and has a thermal conductivit..
Guide Price: £362.16
£434.59 inc VAT
Brand: Kay-Metzeler Model and Size: 2400x1200mm - 34.56m2
Delivery Time: 2 - 3 days
25mm EPS70 Kay-Metzeler boards are produced by cutting expanded foam blocks. Placed above a concrete slab or a precast concrete floor in domestic ground-floor constructions, then finished with a wearing layer of chipboard to satisfy the Building Regulations' U-value requirements. Kay-Metzeler achiev..
£97.52
£117.02 inc VAT
Brand: Jablite Model and Size: 2400x1200 (34.56m2)
Delivery Time: 2 - 3 days
25mm Jablite EPS is a lightweight cellular plastic material suitable for a wide range of building insulation applications. It is an excellent insulating medium which exhibits consistent thermal performance over the range of temperatures normally encountered in buildings. The material is versatile, l..
£119.20
£143.04 inc VAT
30mm Rockwool RW3 Slab (Prorox SL930) - pack of 15
Guide Price
Brand: Rockwool Model and Size: 1200x600mm - 10.8m2
Delivery Time: 1 - 2 days
30mm Rockwool RW3 Slab (Prorox SL 930) is a semi-rigid resin bonded slab, providing great thermal, acoustic and fire resistance, designed to be used in various applications in floors, walls and roofs, including special applications in industrial buildings for insulation of  ships, offshore plat..
Guide Price: £58.64
£70.37 inc VAT
50mm Rockwool RW5 Universal Insulation Slab (Prorox SL960) - pack of 4
Guide Price
Brand: Rockwool Model and Size: RW5 50mm - 2.88m2
Delivery Time: 2 - 3 days
50mm Rockwool RW5 (Prorox SL960) is a high quality resin bonded rigid slab for a wide range of thermal, acoustic and fire insulation requirements both within buildings and for industry. They are suitable for many applications including thermal insulation for floors, walls, roofs and boiler rooms. Th..
Guide Price: £42.82
£51.38 inc VAT
Brand: Thermafleece Model and Size: 13000x370 - 14.43m2 - Free Delivery
Delivery Time: 2 - 5 working days
Thermafleece CosyWool roll is a versatile low density insulation rich in British sheeps wool, which would give you all round performance and value for money. It contains 75% Sheeps wool, 15% recycled polyester and 10% polyester binder with a high recycled content making it highly environmentall..
£100.84
£121.01 inc VAT
Brand: Rockwool Model and Size: 4800x1200mm - 5.76m2
Delivery Time: 3 - 5 weeks
100mm Rockwool RollBatt Loft Insulation is a multi-functional, medium-density lightweight insulation matt, especially designed for improving thermal and acoustic performance, thus reducing fuel consumption and utility bills, when used in roofs, partitions and suspended ceilings. It can be used in nu..
£64.30
£77.16 inc VAT
Brand: EcoTherm Insulation Model and Size: 1200x2400mm - 2.88m2
Delivery Time: 1 - 5 working days
25mm Eco-Versal is a foil faced universal solution for insulating walls, floors, pitched roofs, dormer cheeks and ceilings. It is ideal for insulating timber frame walls and can also be used to insulate solid walls internally. EcoTherm Eco-Versal comprises a fibre free rigid polyisocyanurate (PIR) i..
£26.34
£31.61 inc VAT
Brand: Recticel Model and Size: GP1200x2400 - 2.88m2
Delivery Time: 1 - 5 working days
25mm Eurothane GP comprising a rigid polyisocyanurate (PIR) core faced on both sides with a gas tight multilayer composite aluminium foil facing is the ideal choice for pitched roof, floor or framed wall applications. With a low thermal conductivity value (0.022 W/mK) providing an excellent the..
£19.98
£23.98 inc VAT
25mm Rockwool RWA45 Slab (Prorox SL920) - pack of 16
Guide Price
Brand: Rockwool Model and Size: 600x1200mm - 11.52m2
Delivery Time: 3 - 5 weeks
25mm Rockwool RWA45 is a high quality resin bonded flexible slab for a wide range of thermal, acoustic and fire insulation requirements both within buildings and for industry. They are suitable for many applications including thermal insulation for floors, walls, roofs and boiler rooms. The str..
Guide Price: £28.50
£34.20 inc VAT
7 (0e 0s)
35mm Actis Triso Super 10+ Multi-Foil Insulation
Guide Price
Brand: Actis Model and Size: 1.6x10m - 16m2
Delivery Time: 2 - 3 days
Actis Triso Super 10+ is a thin multi-foil insulation, comprising of even 19 separate layers, including two metallic films with reinforcing mesh, three wadding layers, eight foam layers and six internal reflective films. It has very wide application, but is most suitable for roof and loft insulation..
Guide Price: £188.20
£225.84 inc VAT
50mm EPS100 Polystyrene Insulation Board Jablite (pack of 12)
Guide Price
Brand: Jablite Model and Size: 2400x1200 - 34.56m2
Delivery Time: 1 - 2 weeks
50mm Jablite EPS 100 board is a lightweight and cost efficient product which can be used for insulation of different constructions, including roofs, floors and walls, since it provides constant and stable thermal performance under different temperature conditions. It is made from expanded polystyren..
Guide Price: £189.60
£227.52 inc VAT
50mm Isover Timber Frame Batt 32 (Pack of 9) - 16 Packs per Pallet
Guide Price
Brand: Isover Model and Size: 1175x570 - 96.48m2
Delivery Time: 2 - 4 days
50mm Isover Timber Frame Batt 32 is a high density glass mineral wool slab that reduces heat loss through external walls, improving the energy efficiency and carbon footprint of a building as part of two advanced timber frame systems that can meet Part L Building Regulations (England and Wales)..
50mm Rockwool Flexi Insulation Slab 1200 x 400mm (pack of 12)
Guide Price
Brand: Rockwool Model and Size: 1200x400mm - 5.76m2
Delivery Time: 1 - 2 days
50mm x1200mm x 400mm Rockwool Flexi Insulation Slab is a unique semi-rigid thermal and acoustic insulation product made from volcanic rock. It has a flexible edge, specifically developed using patented technology for a fast and easy, perfect friction fit between timber and metal frame syst..
Guide Price: £30.15
£36.18 inc VAT
Brand: Knauf Model and Size: 1200x5250mm - 151.20m2
Delivery Time: 3 - 5 days
75mm Knauf Earthwool Rafter Roll is an unfaced, semi-rigid roll of glass mineral wool with extra high thermal performance, designed for friction fitting between rafters. Friction fitting allows rafter spacing to be completely filled, thus eliminating air gap. It is specifically designed for ins..
£2,233.68
£2,680.42 inc VAT
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