Kingspan TF70 Thermafloor

If you're insulating a ground floor and need a board that can go anywhere from a shallow refurbishment upgrade to a compliance-driving new-build layer, Kingspan Thermafloor® TF70 covers that whole span from one range.

It's a rigid polyisocyanurate (PIR) board built specifically for solid concrete and suspended timber ground floors, running from 20mm right up to 150mm, all on the same 2400 x 1200mm sheet size. This guide walks through the full range: thermal performance, installation, certification, where each thickness earns its place, and where the range has genuine limits.

Range at a glance

Every board in the range shares the same 2400mm x 1200mm sheet, covering 2.88m² per board. R-values are quoted to BS EN 13165: 2012 + A2: 2016, from a declared thermal conductivity of 0.022 W/mK.

Which thickness should you choose?

Shallow build-ups

20mm, 25mm and 30mm suit refurbishments where floor depth is tight, or work as perimeter upstand material alongside a thicker main board.

Everyday upgrades

40mm, 50mm, 60mm and 70mm are the most commonly specified thicknesses for both solid and suspended timber floors, balancing floor depth against thermal performance.

Underfloor heating and standard new build

75mm, 80mm and 90mm sit below the screed for fast-response underfloor heating, or work as a single layer to hit compliant floor U-values.

Low-energy floors

100mm, 120mm, 125mm, 140mm and 150mm cover strict U-value targets from a single layer, or form the base of a two-layer build-up on the most demanding low-energy specifications.

Why it stands out

• Range depth on one format. Every thickness from 20mm to 150mm ships on the same 2400 x 1200mm board, so ordering, cutting and site handling stay the same whether you're topping up an old solid floor by 20mm or building a low-U-value new-build slab at 150mm.
• Foil-faced both sides. A low emissivity composite foil is autohesively bonded to the PIR core during manufacture, on both faces of every board in the range.
• Floor-grade compressive strength. A declared compressive stress of 120 kPa at 10% compression, enough for most unreinforced floor screeds.
• Works across floor types. Solid concrete ground floors and suspended timber floors alike, without switching product.
• Two-layer combinations for the lowest U-values. Where a single layer isn't enough, Kingspan's own tables show combinations such as 90mm plus 90mm or 90mm plus 100mm for the lowest results.

Thermal performance

Thermal resistance is calculated by dividing board thickness by the 0.022 W/mK conductivity figure, then rounding down to the nearest 0.05 m²K/W. That's why the range runs from 0.90 m²K/W at 20mm up to 6.80 m²K/W at 150mm.

Installation

TF70 is designed to work in four main floor build-ups:

• Below the floor slab. Laid loose-laid and break-bonded over a damp proof membrane on compacted hardcore, with the concrete slab poured directly on top.
• Below the floor screed. Laid over the slab (again over a DPM), then overlaid with a polythene sheet before the screed goes down. That polythene layer, not the board's foil facing, is what acts as the vapour control layer.
• Suspended timber floors, between joists. Supported on 25 x 25mm treated softwood battens, saddle clips or partially-driven nails, cut to fit snugly between joists.
• On battens or as a floating floor. Laid over battens or joists with tongue and grooved chipboard or plywood flooring above, again over a polythene VCL.

Underfloor heating

Where the board sits in the build-up depends on the heating pattern. For a 24-hour heating cycle, TF70 goes below the slab so the concrete's thermal mass evens out the heat over the day. For intermittent heating, where a fast response matters more than steady-state comfort, it's better placed below the screed or below the timber floor, above the slab or beam and block, so there's less thermal mass between the heating pipes and the room.

Fire performance

Under System 4 AVCP, Kingspan Thermafloor® TF70 carries a Euroclass F reaction-to-fire rating to BS EN 13501-1, the lowest classification on that scale. This sits within a fully encapsulated floor build-up (concrete, screed or flooring above and a DPM below), but it's worth factoring in when checking a project's fire strategy.

Certification and standards

• Manufactured to BS EN 13165: 2012 + A2: 2016.
• The current manufactured range, 25mm to 150mm, produced at Kingspan's Pembridge (Herefordshire) and Selby (North Yorkshire) sites, is covered by BBA Certificate 14/5133.
• Manufactured under management systems certified to ISO 9001:2015, ISO 14001:2015, ISO 45001:2018, ISO 50001:2018 and ISO 37301:2021.
• Responsible sourcing certified to BES 6001, rated 'Good'.

Any drawbacks?

• Fire class. Euroclass F is the weakest reaction-to-fire rating on the scale. TF70 sits fully encapsulated in a floor build-up, but this is a factor to weigh in the wider fire strategy.
• Compressive limits. 120 kPa at 10% compression covers most unreinforced screeds, but Kingspan itself recommends its GreenGuard® XPS range where floor loads are excessive.
• DPM is not optional. The foil facing is a thermal facing, not a vapour control layer, and TF70 must always be laid over a proper damp proof membrane, never directly against subsoil.
• Site handling. The reflective foil faces can be slippery when wet, and reflect UV as well as heat, so eye and skin protection is worth considering when installing in bright conditions. Boards shouldn't be walked on unless fully supported by a load-bearing surface below.
• Chemical exposure. The core resists most dilute acids, alkalis and mineral oils short-term, but isn't resistant to some solvent-based adhesives, particularly those containing methyl ethyl ketone.

Our verdict

Thermafloor® TF70 earns its place through range depth rather than any single standout figure: fifteen thicknesses on one board format, taking a job from a 20mm depth-constrained refurbishment through to a 150mm low-energy new build without switching product or supplier. The compressive strength holds up under most screeds, the foil facings and 0.022 W/mK core keep performance consistent across the range, and the installation guidance covers solid and suspended floors and both heating cycles in equal detail. For a floor-specific PIR board that scales with the project rather than forcing a compromise, TF70 is a solid, well-documented choice.