150mm Kingspan Kooltherm K103 Floorboard is the deepest board in the range, sold here as single sheets covering 2.88m² each. At 150mm it gives the highest thermal resistance K103 offers, so it is the board reached for when a floor is being built to a low-energy or near-Passivhaus target, and buying by the sheet lets the order follow the floor area exactly for part floors, irregular bays or topping up.

The board carries a thermal resistance of 7.85 m²K/W, drawn from a fibre-free rigid thermoset phenolic core with a thermal conductivity of 0.019 W/mK. It measures 2400mm x 1200mm, has a square edge and is faced on both sides with glass tissue bonded during manufacture, and holds a compressive strength of 120 kPa to BS EN 826:2013, so it copes with the load of a screed or slab laid over it.

What 150mm offers is the range's strongest figure from one board. Reaching 7.85 m²K/W in a single layer means a demanding low-energy floor is insulated in one pass, with a single set of joints to butt and seal rather than the two offset layers a doubled-up build would call for. Where the build-up depth is there for 150mm, the deepest board keeps the lay-up to a single layer.

150mm Kingspan Kooltherm K103 is used in beam and dense block, suspended timber and solid concrete ground floors, laid over a damp proof membrane and installed in line with the latest Kingspan guidance and the project specification. In suspended timber floors the boards drop between the joists onto battens, saddle clips or nails rather than being fixed over them, with the support height set to suit the 150mm depth. The board works with underfloor heating, and bought as single sheets the board count follows the floor exactly with no leftover full pack to account for.

Key Benefits of Kingspan Kooltherm K103:

• 150mm rigid thermoset phenolic floor board with a fibre-free insulation core, the deepest in the K103 floorboard range.
• Thermal conductivity of 0.019 W/mK.
• Thermal resistance (R-value) of 7.85 m²K/W at 150mm, the highest in the range.
• Compressive strength of 120 kPa to BS EN 826:2013, for use beneath a floor screed or slab.
• Square edge, faced both sides with glass tissue bonded during manufacture.
• Board measures 2400mm x 1200mm, covering 2.88m² per sheet.
• Sold as single sheets, so you order the exact board count the floor needs.
• Suitable for beam and dense block, suspended timber and solid concrete ground floors.
• Compatible with underfloor heating.
• Reaction to fire classification of Euroclass C-s2,d0 to BS EN 13501-1:2018.

Good to know:

• The 7.85 m²K/W figure is the board's thermal resistance, not the finished floor U-value; check the U-value against the full build-up before ordering.
• At 150mm the support height matters: in suspended timber floors set the batten or saddle-clip height so the board sits between the joists, and check threshold and finished-floor clearances before ordering.
• Lay the boards over a damp proof membrane of at least 1200 gauge, keeping the insulation clear of the subsoil.
• K103 resists the passage of water vapour but does not act as a vapour control layer; under a screed, add a separate lapped and taped polythene sheet as the VCL.
• 150mm is the deepest single board in the range; where a build needs more depth, two boards can be laid in a break-bonded pattern with the joints staggered between layers.

Covering a whole floor? The same 150mm board is sold in packs here for bulk ordering.

For a floor reaching a low-energy U-value in a single layer, single sheets let you buy the exact number of 150mm boards the job needs and nothing spare.