150mm Insulation Board EPS150
A 150mm insulation board is typically specified as part of the structural build-up. This is not a finishing layer or a quick thermal upgrade. It is a depth chosen at the design stage to control a building’s thermal behaviour.
What is a 150mm thick insulation board?
A 150mm thick insulation board is a rigid, full-depth insulation panel engineered to fit within a defined structural build-up. Boards this deep are planned in from the start because they influence roof depths, floor levels, and wall build-ups.
Both thickness and material influence the board’s performance. The depth increases the thermal resistance by extending the heat flow path, which is what insulation is meant to do.
Unlike flexible insulation, the 150mm thick insulation board is less prone to sagging or being compressed when correctly installed and supported. It holds its form, which means the insulation layer stays consistent across the whole surface. That consistency helps reduce cold bridging and uneven heat loss problems often associated with gaps, compression, or poor detailing.
These boards are commonly supplied in standard formats such as 2400 x 1200 x 150mm insulation boards and are easy to set out across joists, rafters, or wall zones with minimal cutting.
What is 150mm insulation board used for?
A 150mm insulation thickness board is used where thinner materials would not meet U-value targets without layering.
- Cladding – used behind external cladding systems to control heat loss through the main structure while keeping the outer finish ventilated.
- Flat roofs – Often installed above the deck in warm roof systems. A 150mm roof insulation board keeps the structure warm, reducing condensation risk when correctly detailed with a vapour control layer.
- Pitched roofs – Chosen when rafters allow deeper insulation without complex layering. Installers often use 150mm to help achieve compliance while keeping the build-up straightforward.
- Floors – Used where ground heat loss is a concern, especially on new slabs. It reduces downward heat loss into the ground.
- Heavy-duty floors – Specified on sites expecting higher point loads. At this depth, performance and compressive strength work together when the appropriate compressive strength grade is specified.
- Framing walls – Installed between studs in timber or steel frames to create a deep insulation zone.
- Internal masonry walls – Used where internal space can accommodate deeper build-ups and high thermal resistance is needed without external alterations.
What types of 150mm insulation board are there?
PIR Insulation (Polyisocyanurate)
PIR is often a common choice at this thickness. PIR insulation board 150mm performs well across roofs, walls, and floors while remaining easy to handle and fix.
PIR is valued for its predictable behaviour. It cuts cleanly, fits neatly between structural elements, and works across a range of applications without specialist detailing.
EPS Insulation (Expanded Polystyrene)
EPS is ideal when you need depth without adding unnecessary cost. The material uses trapped air to slow down heat transfer, making it a practical choice where space is available. EPS is typically the most cost-effective option for use in floors and walls when the correct grade is selected and moisture exposure is controlled.
Installers like EPS because it’s light and easy to cut and handle. It’s often specified where large areas need insulating without pushing material costs too high.
XPS Insulation (Extruded Polystyrene)
XPS closed-cell structure resists water uptake far better than most boards.
The board maintains good thermal performance even when conditions are less than ideal, making it a go-to for ground floors and perimeter details.
XPS 150mm is commonly used below slabs and in areas where damp conditions would compromise other materials.
Phenolic Insulation
Phenolic foam is commonly used where high thermal performance is needed in a limited space.
It delivers strong insulation values for its thickness. A 150mm depth helps maximise performance without pushing build-ups beyond acceptable limits.
Phenolic boards are more brittle than PIR; they should be handled carefully during cutting and installation.
Benefits of 150mm insulation board
Here are the benefits of installing a 150mm thick insulation board:
- Strong resistance to heat loss without stacking multiple layers
- Helps buildings meet strict energy standards more easily
- Reduces cold spots by creating a continuous insulation layer
- Suitable for roofs, walls, and floors with planned depth
- Long service life when correctly installed
- Minimal installation errors. Using a single 150mm layer instead of stacking multiple layers reduces detailing errors and installation time.
FAQ
How to fix 150mm insulation board?
Fixing depends on the application, and the goal is to keep the insulation layer continuous.
Fixing 150mm insulation board to the floors
- Prepare your base. The slab or sub-base should be clean and level. Any high spots will keep the board from sitting flat.
- If required, lay a damp-proof membrane.
- Lay the boards flat with joints butted tight and staggered to reduce heat loss paths.
- Fill gaps with compatible insulation or low-expansion foam. Gaps defeat the purpose of the thickness.
- Restrain it with the floor build-up. The screed or floor deck holds the insulation in place. No mechanical fixings are usually needed in standard floor builds.
Fixing 150mm insulation board to the walls
- Ensure that the wall is dry and reasonably flat, as uneven masonry leads to rocking boards and gaps.
- Apply adhesive if specified. Use insulation adhesive in continuous ribbons or a perimeter-and-dab pattern. This helps the board sit flush before mechanical fixing.
- Position the boards. Press boards firmly against the wall, keeping edges tight and aligned. Check for uniformity as you go.
- Mechanically fix the boards, installing the specified number of fixings per board. Fixings should pull the board snug.
- Seal joints. Tape or foam joints as required by the system. This maintains a continuous thermal layer and limits air movement.
Fixing insulation 150mm board to the roofs
Flat roofs (warm roof construction)
- Prepare the deck. The roof deck must be dry and secure. Any movement below will transfer to the insulation.
- Install a fully sealed vapour control layer in line with the roof system design before the insulation is fixed.
- Lay boards tightly, staggering joints. Keep boards flush with no rocking.
- Fix mechanically or bond using approved adhesive, depending on the roof system.
- Apply a waterproof layer. The membrane above restrains the insulation and protects it from weather exposure.
Pitched roofs
- Fit the boards between rafters where applicable. Cut them accurately so they friction-fit without bowing.
- If required, add an under-rafter or over-rafter layer. This helps achieve full coverage and reduces thermal bridging.
- Fix boards securely and seal joints to prevent air leakage before closing the roof build-up.
How to cut 150mm insulation board?
To get clean results, use a fine-tooth saw or insulation saw and support the board fully while cutting. Controlled cutting produces cleaner edges. For PIR or phenolic boards, you can score the facing first, and then cut steadily to avoid tearing the foil.
Where to buy 150mm insulation board?
You can buy a 150mm thick insulation board online from Insulation Wholesale. We sell and supply a full range of 150mm boards from UK stock, with clear pricing and practical support from experts who understand the product better. Our shop is set up for both trade buyers and DIY customers, with reliable availability, honest advice, and fast turnaround.
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150mm Expanded Polystyrene EPS150 Floor Insulation Board 2400mm x 1200mm (8′ x 4′) Pack of 4 (11.52m2)
150mm EPS150, often known as Expanded Polystyrene, is a lightweight foam product produced from tiny polystyrene beads. Due to its high thermal value and simplicity of usage, it is commonly used as one of the most favoured insulation materials in construction.
£200.01£240.01 Ex VATInc VAT£17.36£20.83 Per M2 Add to cart
