Warm roof insulation is used to ensure hot and cold air is not travelling in and out of a residential or commercial building through the roof. Warm roofs give a property more temperature control, meaning it is warmer in the winter and cooler in the summer months. Foam products such as Polyisocyanurate (PIR) bonded with foil or glass tissue facings works particularly well and is often found in modern roof constructions. Warm roof insulation will improve the thermal conductivity of the space. A roof is typically classed as ‘flat’ if it has a pitch below 10°.

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100mm Kingspan Thermaroof TR24 PIR Flat Roof Insulation Board (1200 x 600mm)

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120mm Kingspan Thermaroof TR24 PIR Flat Roof Insulation Board (1200 x 600mm)

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Kingspan Thermaroof TR26 120mm Flat Roof Insulation Board

£159.62 ex VAT

Kingspan Thermaroof TR26 100mm Flat Roof Insulation Board

£203.85 ex VAT

Kingspan Thermaroof TR27 100mm Flat Roof Insulation Board

£137.11 ex VAT

50mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£33.10 ex VAT

90mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£51.70 ex VAT

Kingspan Thermaroof TR26 90mm Flat Roof Insulation Board

£209.09 ex VAT

110mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£53.46 ex VAT

130mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£64.50 ex VAT

140mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£68.80 ex VAT

25mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£23.01 ex VAT

30mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£27.33 ex VAT

40mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£29.02 ex VAT

60mm Recticel Eurodeck Flat Roof Insulation Boards (1200x2400mm)

£36.60 ex VAT

Kingspan Thermaroof TR27 140mm Flat Roof Insulation Board

£94.99 ex VAT

What are the benefits of warm roof insulation?

  • Heat rises, roof insulation will prevent heat escaping through the ceiling and improve the energy efficiency of your home as well as saving you money on energy bills.
  • Up to 30% of your heating can be lost through roofs that do not have the required insulation installed correctly.
  • Warm roof insulation is more effective that cold roof insulation.
  • Roof insulation applied correctly can mean cooler summers and hotter winters, making a more comfortable living or working space at more controlled temperatures.
  • Specific insulation materials designed for certain requirements can also prevent, condensation, mould, rot, or damp, can add an acoustic advantage, and add extra protection with the prevention of fire.
  • Roof insulation when installed correctly can have a lifespan that lasts for as long as the building itself.
  • Warm roof insulation is installed externally. This means it can be installed at any time without affecting the interior of your home.
  • By installing insulation and reducing heat loss, in the long term your home has a positive effect on climate change and environmental impact.

Warm Roof Installation

Warm flat roofs are insulated by externally layering insulation materials on top of the roof rafters. Plywood and vapour check is fixed to the roof and then insulation is applied and tightly butted together and secured using foil tape. Other methods then follow such as more battens, plywood, vapour check (weatherproof sheet), and drip trims etc. This method means no mess or changes need to be made to your home internally and will be an easier form of application for the property owner.

12mm of plywood or OSB board is laid across the timber joists as a base for the flat roof build-up. A vapour control layer is then installed to reduce the risk of condensation and moisture compromising the roofs’ structure.

The vapour control layer (VPL) is marked where fixings will pierce the membrane (this is seen at rafter centres and at the correct axial spacing). Tape is added at each point where the vapour control layer will be pierced to create a seal.

The required thickness of insulation is laid on top of the VPL. A second layer of plywood or OSB board is added. The deck is then fixed together with the fixings piercing through every layer of build-up. The final step is to install a waterproof membrane to finish off the deck and protect the build-up from wind and driven rain

Cold Roof vs Warm Roof.

A warm roof is the easiest and most cost-effective type of insulation and is an ideal choice for pitched roofs. Cold roof insulation however can be a solution where increasing the property height isn’t possible such as flat roof extensions and balconies.

  • Cold roof is when the insulation is fitted in between the rafters of the roof and timber deck is applied over the top along with weatherproof coverings. This method is referred to as cold roof as cold spots can occur at the rafters causing thermal bridging.

Using a cold roof technique can mean having to replace boards on the roofs surface.

  • Warm roof is when timber deck is applied directly to the rafters and then insulation is layered on top. This method is referred to as warm roof as due to application of insulation it prevents thermal bridging. See video below.

Installing a cold roof is more work, takes longer and does not provide great thermal conductivity. A warm roof is a quick and easy application that provides great thermal conductivity. A warm roof is a method used by most building professionals.

When installing roof insulation take safety measures to ensure insulation is fitted correctly around electrical sockets, wires and ventilation spaces, or the correct procedures are put into place to remove these components.

Always consult a building professional when insulating your roof to prevent the wrong insulation from being installed and the possibility of damaging your property.

Some roofs are harder to reach and not accessible in which case a specialist can be called in with the correct tools to insulate the roof.

Warm Roof FAQs

How does a warm roof work?

A warm roof construction has many benefits over a traditional 'cold roof', essentially it is a 'breathable roof construction', which allows moisture to escape which in turn prevents dampness and any associated decay and rot problems.

Can you insulate under a warm roof?

It is advised that you should always insulate between and above the rafters (warm roof) or between and under the rafters (cold roof). Not all three to allow breathable space.

Warm Roof Insulation Products

Kingspan TR27 is part of the Thermaroof range designed for the insulation of flat roofs. Specifically flat roofs, waterproofed with fixed single-ply waterproofing. The Kingspan TR27 PIR board is suitable for new builds, extensions, and refurbishments. The installation technique creates a flat roof insulation solution for fast-track building programmes.

  • 1200mm x 600mm
  • Thicknesses, 25mm – 150mm
  • Thermal Conductivity: 0.022W/mK – 0.027W/mK
  • Material: Polyisocyanurate, Glass tissue

Another good warm roof insulation product is Eurodeck by Recticel. It is extremely durable and when installed correctly can provide reliable long term thermal performance that will continue to last for the entire lifetime of the building. Eurodeck helps to provide a more temperature-controlled environment meaning warmer winters and cooler summers.

  • 2400mm x 1200mm
  • Thicknesses, 25mm – 160mm
  • Thermal Conductivity: 0.022W/mK
  • Material: Polyisocyanurate (PIR), Low Composite Foil