Insulation Boards

Discover high quality insulation boards for interior walls, exterior walls, floors, and roofs. Improve thermal efficiency, reduce energy bills, and enjoy lasting comfort with trusted insulation materials from EWI Store. Whether you need a single insulation board or a full range of insulation panels for a larger project, we can help you choose the right insulation boards for the job.

Why choose insulation boards?

Insulation boards form a consistent heat barrier that helps to prevent heat from escaping and to reduce heat transfer through the fabric of the building. Used on external walls, interior walls, and floors, they support thermal insulation, airtightness, and sound reduction. In practice this leads to better thermal and airtightness performance, lower energy bills, and a smoother route to target U values. You can select insulation sheets in a wide choice of thicknesses, so the same thickness does not always give the same thermal performance across different materials. Generally speaking, materials with low thermal conductivity provide higher performance for the same thickness.

Types of insulation board

Choosing between the different types of insulation depends on location, thermal performance targets, moisture behaviour, and budget. The summaries below explain each type of insulation and when to use it.

EPS insulation boards

EPS, or expanded polystyrene, is a lightweight option for external walls and solid wall upgrades. It is easy to cut, simple to handle, and offers dependable insulation properties. It is widely used to insulate cavity walls on refurbishment projects where you fill cavity wall sections or add insulation to the exterior side of solid masonry. See the product page for sizes and details: EPS Insulation Board, 0.72 m².

XPS insulation boards

XPS, or extruded polystyrene, offers strong moisture resistance and excellent compressive strength, so it is well suited to timber floors, uninsulated floor upgrades, and flat roof insulation. It resists water uptake, so it will not readily absorb water during service, and it helps to reduce heat loss where floors meet exterior walls. View the product page: XPS Insulation, 1 board.

PIR insulation boards

PIR insulation boards provide premium thermal performance due to their low thermal conductivity. PIR boards are often used as a roof insulation board between roof rafters on a pitched roof, or on the interior side of walls where space is tight. If you are comparing PIR boards with other materials, note that PIR can deliver the target result at a lower thickness. Explore: Kingspan Kooltherm K5 External Wall Board, 0.72 m². Kingspan Kooltherm options also include specialised products for roofs, such as the K107 pitched roof board, which is designed to fit between roof rafters and around wooden joists where depth is limited.

Fire resistant insulation boards

Where fire performance matters, mineral wool boards are a reliable choice. They combine thermal insulation with a high reaction to fire classification, which is valuable in commercial buildings and multi storey projects. See: Rocksilk EWI Slab, Rock Mineral Wool, 90 mm and Rockwool External Wall Dual Density Slab.

Foam insulation and rigid boards

Rigid foam board solutions cover a broad family, including rigid foam insulation board for floors, walls, and roofs. These rigid insulation boards are easy to handle, offer strong thermal performance, and can deliver useful soundproofing properties. Suitable options include XPS Insulation, 1 board and Kingspan Kooltherm K5 External Wall Board, 0.72 m². If you prefer foam insulation as an insulation foam board for the interior side of a wall lining, review the substrate, service runs, and finish requirements before you purchase insulation boards.

Internal, cavity, and roof applications

Cavity wall insulation aims to reduce heat loss through two walls separated by an air space. You can insulate cavity walls by adding suitable insulation panels in the cavity, or by applying insulation to the exterior walls in a solid wall system. Internal wall insulation is common where you need to upgrade insulating walls from the interior side while maintaining a smooth finish. For flat roofs, choose materials with strong moisture resistance and compressive strength. For a pitched roof, a roof insulation board can sit between or below roof rafters, with careful detailing around wooden joists to maintain continuity.

Insulation board buying guide

When comparing wall insulation boards, floor insulation, and roof insulation, focus on the following points:

Thermal conductivity and thermal performance
A lower declared thermal conductivity indicates better performance, which improves overall energy efficiency. Materials with low thermal conductivity reach target values at reduced thickness compared with other materials.

Moisture resistance and water behaviour
Flat roofs and timber floors benefit from materials with robust moisture resistance. Some materials can absorb water if left unprotected, which reduces performance, so design the full build up carefully.

Strength, span, and fixings
Rigid boards are chosen for their stiffness and ease of fixing, but the substrate matters. Consider compressive strength on floors and choose suitable fixings for exterior walls and interior walls.

Cost and availability
The right insulation boards can reduce construction costs through simpler build ups and faster installation. Rigid foam can be economical for large areas, while premium products like Kingspan Kooltherm may reduce thickness and help control construction costs where space is tight.

Compatibility
Match the type of insulation to the area. For example, XPS works well on uninsulated floor projects and flat roofs, while PIR boards suit cavities and linings where space is limited. EPS is a dependable choice for external walls in refurbishment.

For further reading: Mineral Wool vs EPS and Mineral Wool vs EPS vs Kingspan K5 vs Wood Fibre.

Installing insulation boards

Successful installing insulation boards starts with preparation. Ensure the substrate is clean, sound, and dry, then mark out services and cut slots where required. Apply the appropriate adhesive or mechanical fixings, press the boards firmly into place, and seal outer edges and board joints to help prevent heat bypass. On a cavity wall, fill cavity wall sections fully and close gaps to reduce heat loss and reduce noise pollution. On roofs, detail around roof rafters and wooden joists to maintain continuity. For exterior finishes, two flexible layers of reinforced basecoat can help achieve a smooth finish over the boards. For guidance specific to fixing on walls, see Fixing insulation boards to walls. You can also source insulation fixings and insulation accessories.

Frequently asked questions

What is the difference between insulation materials at the same thickness?
Different materials have different thermal conductivity values, so thermal performance varies even at the same thickness.

Can rigid foam be used on floors?
Yes. Rigid foam and rigid boards are commonly used on floors, including timber floors, with attention to load, moisture, and the interface with exterior walls.

Will insulation reduce noise pollution?
Insulation can reduce noise pollution. Some systems provide notable soundproofing properties in addition to thermal benefits.

Which product should I choose for a flat roof?
For flat roof insulation, XPS and other rigid foam board solutions are popular due to moisture resistance and compressive strength.

What about internal wall insulation?
Internal wall insulation is useful where you cannot change the exterior. A rigid foam insulation board or PIR boards on the interior side can improve comfort and prevent heat loss, provided you manage vapour and airtightness layers correctly.

Why buy from EWI Store?

We supply a wide range of insulation for walls, floors, and roofs. Our catalogue includes EPS insulation boards for external walls, XPS for floors and flat roofs, and Kingspan Kooltherm for slim build ups. We offer expert advice for homeowners and commercial buildings, and our product guidance helps you select the right insulation boards to reduce heat loss and reduce construction costs without compromising quality.

Ready to purchase insulation boards?

If you are ready to purchase insulation boards, explore the specific products linked above or contact us for tailored advice on cavity wall insulation, internal wall insulation, and roof insulation. The right choice will help prevent heat, improve energy efficiency, and deliver long term performance across the fabric of your property.