Roof Insulation Board

Here at Materials Market, we stock only the best roof insulation brands on the market; Celotex, EcoTherm, and Kingspan to name a few. With thermal conductivity values as low as 0.022 W/mk, our roof insulation board range offers excellent protection against costly heat loss. Despite their strength, the boards are equally lightweight, easily handled and effortlessly cut with a plasterboard saw. Our rigid roof thermal insulation boards are ideal for both flat and pitched roofs. 

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What are Roof Insulation Boards?

Roof insulation boards, otherwise known as roof insulation panels, are insulation boards that are tailor-made for pitched and flat roofs. There are a host of different insulation types available on the market but the most common roof thermal insulation material is PIR. 

Polyisocyanurate is one of the most mass-produced insulation materials in the insulation industry. Its thermal conductivity value of 0.022 W/mK makes it one of the best materials for trapping heat inside a property.


Despite their thermal efficiency, insulation boards for loft roofs do not have to stand alone. You can use additional products to enhance their thermal performance. Both foil and acrylic tape can be used to seal the space between boards; this ensures that the thermal properties of the boards are not compromised. 

Foil and acrylic tape are also good options for people who want to repair wear and tear damage on roof insulation panels in order to keep the roof as efficiently insulated as possible.

General Purpose Roof Insulation Panels

Around 25% of the heat in a property is lost through its roof. Roof insulation boards are a preventative measure to help curtail heat loss and improve the overall thermal envelope of roof space. They are ideal for both domestic and commercial uses.

The Celotex Insulation Board range contains general-purpose boards that can be used in floors, walls and roofs. They can even be installed under floorboards and in cavity walls. These PIR boards are rigid, lightweight, and have a low-emissivity foil facing to reduce heat loss.

General purposes boards are a good choice for people who want all the thermal benefits that come with PIR boards without having to research specific, purpose-built panels.

Pitched Roof Insulation Boards

In general, pitched roofs are more thermally efficient than flat roofs due to the gap found between the flat interior and the pitched exterior; this gap allows for ventilation.

You can install PIR insulation board between rafters and on the underside of the roof. Both Celotex and EcoTherm are popular choices for people who have pitched roofs. Their PIR insulation boards have a low thermal conductivity value of 0.022 W/mK, which means they retain heat well within the building structure.

EcoTherm is one of the most trusted manufacturers of PIR insulation boards. The EcoTherm Eco-Versal PIR insulation boards range features fibre-free PIR rigid insulation boards that are comprised of an insulating core that is faced with aluminium foil on both sides. They do not sag or rot and are easy to cut and fit. You can manipulate these boards to sit around and between rafters as you see fit.

Flat Roof Insulation Boards

Flat roofs are less popular than pitched roofs. They are most common in areas that have high winds; a flat roof has far more durability against high winds than pitched roofs with fragile tiles.

We stock a host of insulation boards geared towards insulating flat roofs. Kingspan’s Thermaroof range is perfect for people who want to create a thermal barrier between their home and their flat roof. Kingspan Thermaroof TR27 roof insulation panels have a thermal conductivity of 0.024 W/mK. They can be covered with fully adhered single-ply, partially bonded built-up felt, mastic asphalt, and cold liquid applied waterproofing. On the other hand, Kingspan’s Thermaroof TR24 can be used in conjunction with torch-on felt. In terms of flat roof insulation boards, Kingspan is the most reliable manufacturer on the market.

Frequently Asked Roof Insulation Panel Questions

What Are the Benefits of Roof Insulation Panels?

The benefits of roof insulation are vast and plenty, the main one being thermal performance. Roof insulation board costs pay for themselves when you consider the heat-saving benefits of installing them. 
You can trap up to a third of the heat in your home when you invest in roof insulation boards. Not only will this keep your home toastier for longer, but you will also save money on energy bills in the long run; a welcome benefit amid the current energy crisis.

Insulation boards for loft roofs (pitched roofs) typically have a life span of 40 years. The likelihood is that you will not have to invest in roof insulation panels twice. You might even be eligible for government assistance for the cost of the boards, which makes the lump sum payment even less daunting. The Green Homes Grant provides eligible homeowners with vouchers for energy-efficient improvements.

The less energy you use, the less carbon dioxide you produce. Eco-conscious individuals invest in pitched and flat roof insulation boards to improve the carbon footprint of their homes.

How to Cut Roof Insulation Boards?

There are lots of different ways that you can cut roof insulation boards to size. Most boards can usually be cut with a simple utility knife, although you can also use a manual or electronic saw in a safe construction environment. We recommend cutting insulation boards in a dedicated construction space that is both spacious and organised.

You should always contact a professional when cutting insulation materials. They will have up-to-date training and can recommend the best techniques for your specific insulation needs.

How to Install Roof Insulation Boards?

We stock roof insulation boards for pitched roofs and flat roofs, which are relatively easy to install.

Installing flat roof insulation boards is simple. People who have flat roofs do not have to deal with awkward slants or difficult corners. Simply put the boards in place and secure them with screws that have large washers. Some people also use spray foam or caulk to hold smaller insulation boards in place.

People with pitched roofs can put roof insulation boards between rafters on the underside of the roof. Once the boards are in place, you can secure them in the same way that you would secure flat roof insulation boards.

If you are also looking for loft insulation in addition to insulated roofing sheets, you can find our range of rolls and boards here.

Are Roof Insulation Boards Waterproof

Although PIR rigid foam board is typically water-resistant, it is not entirely waterproof. You should avoid exposing PIR boards to rain or installing them in applications where they will be exposed to water.