Flat Roof Insulation
Flat roof insulating materials are fitted on or within roofs to control the transmission of heat through roofing materials. This insulation works on both modern and traditional flat roofing systems. It can be installed during new builds or retrofitted to upgrade thermal performance.
What is roof insulation flat roof?
These insulation products are meant for flat roofing systems only. Due to their low pitch and limited ventilation, flat roofs require insulation that carefully manages heat and moisture.
The insulating material can be added under, above, or between the roofing structure. These are known as cold, warm, or inverted flat roof systems. However, the most popular method in the UK covers warm flat roofs, where the insulation is fitted above the deck.
What is warm flat roof insulation used for?
Insulation for warm flat roofs primarily:
- Boosts the building’s energy performance.
- Maintains a warm roof deck.
- Protects the roof from temperature swings and condensation.
It can be used on many buildings with warm flat roofs, whether domestic, commercial, or refurbishment projects. It is commonly used in garages, extensions, garden rooms, offices, schools, and warehouses.
Types of warm flat roof insulation in UK
Insulation Wholesale offers an extensive range of flat roof insulation materials. All products are suitable for warm flat roof systems in line with UK Building Regulations.
Our most popular offerings include:
- PIR insulation boards: Lightweight, rigid, and highly efficient. Perfect for warm roof systems.
- EPS insulation (expanded polystyrene) boards: Cost-effective, moisture-resistant, and easy to install.
- XPS insulation (extruded polystyrene) boards: Are durable and dense. They are perfect for roofs exposed to heavy use or loads and are also commonly used in inverted roofs.
- Mineral wool insulation roof slabs: Robust, easy to cut, acoustic, and fire resistant. They are suitable for specific roofing specifications.
Benefits of using insulation for flat roofs
Depending on material choice and roof design, insulated flat roofs offer the following benefits:
- Superior thermal efficiency.
- Less condensation.
- Fire and sound protection.
- Reduced energy bills.
- Extended roof lifespan.
- An eco-friendly upgrade.
Why choose our flat roof insulation?
Here’s what makes Insulation Wholesale the trusted choice for flat roof insulation in the UK:
- Premium products from trusted UK brands.
- Quality guaranteed to meet UK regulations.
- Full range of accessories and compatible materials.
- Competitive flat roof insulation prices.
- Expert advice for both trade and DIY.
- Enjoy fast, reliable nationwide delivery within 1–3 working days, unless stated otherwise.
Are you installing a new roof or upgrading an old one? We’ll help you choose the right insulating product efficiently, affordably, and without compromise. Shop online now or contact our insulation experts for tailored advice.
FAQ
What is flat roof insulation?
This is the layer of thermal material added to a flat or low-sloped roof to improve heat retention and promote efficient energy use. This system helps meet current UK Building Regulations for energy efficiency.
Insulating a flat roof can also help sustain comfortable indoor temperatures and minimise condensation within the roof structure.
How much insulation is required for a flat roof?
The amount of insulation material depends on your desired U-value and roof design. The recommended U-value for most UK applications is 0.18 W/m²K. This typically requires between 130mm and 180mm of PIR insulation, though the thickness varies based on the material.
Always confirm thickness with a qualified installer to ensure compliance with your specific roof design and U-value target.
How much does flat roof insulation cost?
Material, thickness, and total roof area affect flat roof insulation cost. Materials like PIR and phenolic panels are more costly per sheet, but they deliver higher thermal efficiency; therefore, you may need less material overall. Check our online store or contact our team for a personalised quote for the best deal.
How thick should flat roof insulation be?
Most flat roofs in the UK need 130mm–180mm of insulating material to meet current building standards. The exact thickness depends on your chosen material and roof structure. PIR require less thickness to achieve the same level of performance as EPS/XPS or mineral wool.
Showing 1–32 of 248 results
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100mm Celotex GA4100 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
100mm Celotex GA4100 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£26.49£31.79 Ex VATInc VAT£9.20£11.04 Per M2 Add to cart -
100mm Ecotherm Eco-Versal Rigid PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
100mm Ecotherm Eco-Versal is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Ecotherm Eco-Versal is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£26.67£32.00 Ex VATInc VAT£9.26£11.11 Per M2 Add to cart -
100mm Kingspan Kooltherm K107 Pitched Roof Board 2400mm x 1200mm Pack of 3 (8.64m2)
100mm Kingspan Kooltherm K107 Pitched Roof Board is a premium performance insulation with a fibre-free rigid thermoset phenolic core. It is used to insulate pitched roofs and attic spaces, and has a thermal conductivity of just 0.019 W/m.K across all thicknesses.
£289.16£346.99 Ex VATInc VAT£33.47£40.16 Per M2 Add to cart -
100mm Kingspan Therma TP10 / TF70 / TW55 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 3 (8.64m2)
All three models 100mm Kingspan Therma PIR Insulation Board:
- 100mm Thermapitch TP10
- 100mm Thermafloor TF70
- 100mm Thermawall TW55
share the same high-performance PIR core and low-emissivity foil facings, offering excellent thermal efficiency and easy installation. Although labeled differently, these boards share identical technical specifications.
£138.93£166.72 Ex VATInc VAT£16.08£19.30 Per M2 Add to cart -
100mm Kingspan Thermaroof TR24 Flat Roof PIR Insulation Board 1200mm x 600mm Pack of 5 (3.60m2)
100mm Kingspan Thermaroof TR24 is a high performance insulation with a fibre-free rigid thermoset polyisocyanurate (PIR) core. Kingspan Thermaroof is suitable for flat roofs waterproofed with partially bonded torch applied multi-layer bituminous waterproofing.
£89.36£107.23 Ex VATInc VAT£24.82£29.78 Per M2 Add to cart -
100mm Kingspan Thermaroof TR26 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 3 (8.64m2)
100mm Kingspan TR26 Thermaroof is high-performance insulation that has a fiber-free rigid thermoset polyisocyanurate (PIR) core. Suitable for flat roof application waterproofed with mechanically fixed single-ply waterproofing.
£187.37£224.84 Ex VATInc VAT£21.69£26.03 Per M2 Add to cart -
100mm Kingspan Thermaroof TR27 PIR Insulation Board 1200mm x 1200mm Pack of 4 (5.76m2)
100mm Kingspan Thermaroof TR27 is a high performance insulation with a fibre-free rigid thermoset polyisocyanurate (PIR) core. It is used to insulate flat roofs waterproofed with fully adhered single-ply, partially bonded built-up felt, mastic asphalt and cold liquid applied waterproofing.
£130.16£156.19 Ex VATInc VAT£22.60£27.12 Per M2 Add to cart -
100mm Recticel Eurothane Eurodeck Insulation Board 2400mm x 1200mm Pack of 4 (11.52m2)
100mm Eurothane® Eurodeck is compatible with mechanically fixed single-ply systems, benefiting from high compressive strength and excellent dimensional stability that ensures the flat surface finish required for optimum performance in new build and refurbishment projects. It is faced on both sides with a multi-layer coated aluminum foil.
£163.45£196.14 Ex VATInc VAT£14.19£17.03 Per M2 Add to cart -
100mm Recticel Eurothane GP PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
100mm Recticel Eurothane GP is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Recticel is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£26.64£31.97 Ex VATInc VAT£9.25£11.10 Per M2 Add to cart -
100mm Recticel Powerdeck F Flat Roof Insulation Board 1200mm x 600mm Pack of 5 (3.60m2)
100mm Powerdeck F flat roof insulation board is compatible with multiple waterproofing systems, benefiting from high compressive strength and excellent dimensional stability. Both sides of Powerdeck F are faced with a mineral coated glass fleece.
£59.13£70.96 Ex VATInc VAT£16.43£19.72 Per M2 Add to cart -
100mm Recticel Powerdeck U Flat Roof Insulation Board 1200mm x 600mm Pack of 5 (3.60m2)
100mm Powerdeck U flat roof insulation board is a high performance rigid PIR insulation board for use in warm flat roofs with bituminous torch-on felt waterproofing systems. Both sides of Powerdeck U are faced with a bituminous coated glass fleece.
£62.83£75.40 Ex VATInc VAT£17.45£20.94 Per M2 Add to cart -
100mm Rockwool Flexi Slab Acoustic Insulation 1200mm x 600mm 4.32m2 Pack
100mm Rockwool Flexi has been designed as a multi-use, dual-purpose acoustic and thermal mineral wool insulation with a unique flexible edge along one side. It is suitable for use all over the home, in pitched roof rafters, framed external walls, internal partitions, intermediate floors, separating walls and floors, and timber suspended ground floors.
£40.41£48.49 Ex VATInc VAT£9.35£11.22 Per m2 Add to cart -
100mm Rockwool RWA45 Acoustic Insulation Slab 1200 x 600mm 2.88m2 Pack
100mm Rockwool RWA45 has been developed for thermal, acoustic and fire performance in a range of construction types. It is suitable for applications on partition walls, ceilings, floors and roofs.
£21.39£25.67 Ex VATInc VAT£7.43£8.92 Per m2 Add to cart -
110mm Celotex XR4110 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
110mm Celotex XR4110 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£32.42£38.90 Ex VATInc VAT£11.26£13.51 Per M2 Add to cart -
110mm Ecotherm Eco-Versal Rigid PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
110mm Ecotherm Eco-Versal is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Ecotherm Eco-Versal is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£32.42£38.90 Ex VATInc VAT£11.26£13.51 Per M2 Add to cart -
110mm Kingspan Thermaroof TR26 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 3 (8.64m2)
110mm Kingspan TR26 Thermaroof is high-performance insulation that has a fiber-free rigid thermoset polyisocyanurate (PIR) core. Suitable for flat roof application waterproofed with mechanically fixed single-ply waterproofing.
£212.43£254.92 Ex VATInc VAT£24.59£29.51 Per M2 Add to cart -
110mm Recticel Eurothane Eurodeck Insulation Board 2400mm x 1200mm Pack of 3 (8.64m2)
110mm Eurothane® Eurodeck is compatible with mechanically fixed single-ply systems, benefiting from high compressive strength and excellent dimensional stability that ensures the flat surface finish required for optimum performance in new build and refurbishment projects. It is faced on both sides with a multi-layer coated aluminum foil.
£133.69£160.43 Ex VATInc VAT£15.47£18.56 Per M2 Add to cart -
110mm Recticel Eurothane GP PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
110mm Recticel Eurothane GP is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Recticel is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£32.42£38.90 Ex VATInc VAT£11.26£13.51 Per M2 Add to cart -
110mm Unilin Thin-R PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pallet of 21 (60.48m2)
110mm Unilin Thin-R PIR insulation is a foil faced, high-performance insulation solution that offers exceptional thermal efficiency and durability. This polyisocyanurate insulation board, formerly known as Xtratherm, is ideal for a range of applications, such as floors, pitched roofs, and walls.
POA Get a quote -
120mm Celotex XR4120 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
120mm Celotex XR4120 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£32.75£39.30 Ex VATInc VAT£11.37£13.64 Per M2 Add to cart -
120mm Ecotherm Eco-Versal Rigid PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
120mm Ecotherm Eco-Versal is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Ecotherm Eco-Versal is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£32.44£38.93 Ex VATInc VAT£11.26£13.51 Per M2 Add to cart -
120mm Kingspan Kooltherm K107 Pitched Roof Board 2400mm x 1200mm Pack of 2 (5.76m2)
120mm Kingspan Kooltherm K107 Pitched Roof Board is a premium performance insulation with a fibre-free rigid thermoset phenolic core. It is used to insulate pitched roofs and attic spaces, and has a thermal conductivity of just 0.019 W/m.K across all thicknesses.
£235.38£282.46 Ex VATInc VAT£40.86£49.03 Per M2 Add to cart -
120mm Kingspan Therma TP10 / TF70 / TW55 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 2 (5.76m2)
All three models 120mm Kingspan Therma PIR Insulation Board:
- 120mm Thermapitch TP10
- 120mm Thermafloor TF70
- 120mm Thermawall TW55
share the same high-performance PIR core and low-emissivity foil facings, offering excellent thermal efficiency and easy installation. Although labeled differently, these boards share identical technical specifications.
£111.30£133.56 Ex VATInc VAT£19.32£23.18 Per M2 Add to cart -
120mm Kingspan Thermaroof TR24 Flat Roof PIR Insulation Board 1200mm x 600mm Pack of 4 (2.88m2)
120mm Kingspan Thermaroof TR24 is a high performance insulation with a fibre-free rigid thermoset polyisocyanurate (PIR) core. Kingspan Thermaroof is suitable for flat roofs waterproofed with partially bonded torch applied multi-layer bituminous waterproofing.
£80.59£96.71 Ex VATInc VAT£27.98£33.58 Per M2 Add to cart -
120mm Kingspan Thermaroof TR26 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 2 (5.76m2)
120mm Kingspan TR26 Thermaroof is high-performance insulation that has a fiber-free rigid thermoset polyisocyanurate (PIR) core. Suitable for flat roof application waterproofed with mechanically fixed single-ply waterproofing.
£142.77£171.32 Ex VATInc VAT£24.79£29.75 Per M2 Add to cart -
120mm Kingspan Thermaroof TR27 PIR Insulation Board 1200mm x 1200mm Pack of 4 (5.76m2)
120mm Kingspan Thermaroof TR27 is a high performance insulation with a fibre-free rigid thermoset polyisocyanurate (PIR) core. It is used to insulate flat roofs waterproofed with fully adhered single-ply, partially bonded built-up felt, mastic asphalt and cold liquid applied waterproofing.
£144.44£173.33 Ex VATInc VAT£25.08£30.10 Per M2 Add to cart -
120mm Recticel Eurothane Eurodeck Insulation Board 2400mm x 1200mm Pack of 4 (11.52m2)
- 120mm Eurothane® Eurodeck is compatible with mechanically fixed single-ply systems, benefiting from high compressive strength and excellent dimensional stability that ensures the flat surface finish required for optimum performance in new build and refurbishment projects. It is faced on both sides with a multi-layer coated aluminum foil.
£198.33£238.00 Ex VATInc VAT£17.22£20.66 Per M2 Add to cart -
120mm Recticel Eurothane GP PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
120mm Recticel Eurothane GP is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Recticel is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£32.43£38.92 Ex VATInc VAT£11.26£13.51 Per M2 Add to cart -
120mm Recticel Powerdeck F Flat Roof Insulation Board 1200mm x 600mm Pack of 4 (2.88m2)
120mm Powerdeck F flat roof insulation board is compatible with multiple waterproofing systems, benefiting from high compressive strength and excellent dimensional stability. Both sides of Powerdeck F are faced with a mineral coated glass fleece.
£55.50£66.60 Ex VATInc VAT£19.27£23.12 Per M2 Add to cart -
120mm Recticel Powerdeck U Flat Roof Insulation Board 1200mm x 600mm Pack of 4 (2.88m2)
120mm Powerdeck U flat roof insulation board is a high performance rigid PIR insulation board for use in warm flat roofs with bituminous torch-on felt waterproofing systems. Both sides of Powerdeck U are faced with a bituminous coated glass fleece.
£57.08£68.50 Ex VATInc VAT£19.82£23.78 Per M2 Add to cart -
125mm Kingspan Therma TP10 / TF70 / TW55 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 2 (5.76m2)
All three models 20mm Kingspan Therma PIR Insulation Board:
- 125mm Thermapitch TP10
- 125mm Thermafloor TF70
- 125mm Thermawall TW55
share the same high-performance PIR core and low-emissivity foil facings, offering excellent thermal efficiency and easy installation. Although labeled differently, these boards share identical technical specifications.
£128.56£154.27 Ex VATInc VAT£22.32£26.78 Per M2 Add to cart -
130mm Celotex XR4130 PIR Insulation Board 2400mm x 1200mm (8′ x 4′) 2.88m2
130mm Celotex XR4130 is a polyisocyanurate (PIR) insulation core with composite aluminium foil facings on both sides. Celotex is a multi-purpose insulation board suitable for use in pitched roofs, ceilings, floors and walls.
£38.80£46.56 Ex VATInc VAT£13.47£16.16 Per M2 Add to cart
