Kingspan Kooltherm K3 Underfloor Board

From: $600.11

Kingspan Kooltherm K3 Floorboard is a thin underfloor insulation board. It can be used under concrete slabs and is ideal for both new build and refurbishment projects.

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Kingspan Kooltherm K3 Floor Insulation Panels

Kingspan Kooltherm K3 Floorboard is a super high performance, fibre-free rigid thermoset closed cell phenolic insulation core, sandwiched between an upper tissue-based facing and a lower facing of highly reflective aluminium foil autohesively bonded to the insulation core during manufacture. Kooltherm K3 Floorboard is manufactured without the use of CFCs/HCFCs and has zero Ozone Depleting Potential (ODP) and low Global Warming Potential (GWP).

K3 Floor Insulation – Key Benefits

  • Super high performance rigid thermoset phenolic insulation
  • Fibre-free, closed cell insulation core
  • Resistant to the passage of water vapour
  • Easy to handle and install floor board insulation
  • Ideal for new build and refurbishment
  • Suitable as a concrete floor insulation
  • Manufactured with a CFC/HCFC-free blowing agent that has zero ODP and low GWP
  • Compliant with AS/NZS 4859.1
  • CodeMark certified
  • FM Approved
  • Group 1 BCA fire classification

Insulation for Concrete Floors and Suspended Ground Floors

Did you know you can lose up to 10% of your heat through your floor? Installing underfloor insulation at the ground level of your house can vastly reduce heat loss and create a more comfortable floor temperature for you and your family to walk on. Depending if your floor in you home is ground bearing or a suspended floor installation of insulation can vary. For new and existing homes with suspended timbers floors which can’t be accessed from below the floorboards can be removed from above to allow for insulating under floorboards with Kooltherm K3 Floorboard between each floor joist. Kingspan Kooltherm K3 Floorboard is a premium performance rigid thermoset phenolic insulation board for use with solid concrete and suspended ground floors can be placed directly onto the concrete floor. Before the existing floorboards are reinstated a fully sealed vapour control layer is installed above the floor joists, below the floorboards thus making the floor vapour tight and airtight. At all times adequate and unobstructed ventilation must be maintained to the underside of the suspended timber floor joists.For new houses with which have a solid ground bearing concrete floor construction a continuous damp-proof membrane/radon barrier beneath is required beneath the insulation or below the structural floor slab, taking care to overlap with any damp-proof course in the external walls. Then the premium performance  Kingspan Kooltherm K3 Floorboard can be placed directly onto the damp proof membrane or concrete floor slab. The Kooltherm K3 Floorboard is then overlaid with a separation layer before the installation of the floor screed.

Why Use K3 Floor Slab Insulation in New Constructions?

•    It reduces heat loss through the floor

•    Minimizes thermal bridging

•    Makes the concrete floor part of the thermal mass of the conditioned space, thereby reducing interior temperature swings.

•    Makes your home feel more comfortable and easier to heat.

What are the Benefits of Kooltherm K3 in Existing Constructions?

•    Will reduce heat loss

•    Help towards reducing energy costs

•    Reduce draughts due to the installation of a vapour control layer.

•    Make your home feel more comfortable and easier to heat.

Product Range


Frequently Asked Questions

What is Kooltherm?

The Kingspan Kooltherm range is an extensive range of high performance rigid thermoset phenolic insulation for roofs, walls and floors.


Kingspan Kooltherm offers among the most thermally efficient conductivity and thermal performance values available, which means you can minimise the thickness of your insulation compared to other conventional insulation to achieve the same performance.


Kingspan Kooltherm also has exceptional fire performance characteristics. As it is a thermoset material, it hardens and chars in fire situations, giving off very little smoke; unlike thermoplastics, such as polystyrene which melt, soften, and give off thick black smoke.

What is phenolic insulation?

Phenolic insulation, like our Kooltherm range of products, is the most thermally efficient insulation commonly used. It is made through a manufacturing process where a rigid thermoset foam forms an insulating core between two facing elements, for example, a low emissivity composite foil.


Choosing a phenolic insulation will make it easier to reach those high target R-values with a minimal thickness of insulation.

Are Kingspan insulation boards affected by water or moisture?

Our Kooltherm and Therma ranges are closed-cell types of insulation. This type of insulation is resilient to the occasional light sprinkle of water but should always be kept and stored in dry conditions to maximise its thermal performance.


In cases where insulation is expected to get wet or where it is to be installed outside any tanking membrane, we recommend using Kingspan GreenGuard, which isn’t negatively affected by groundwater or moisture.

Why is a 40mm cavity needed in a double brick cavity wall for K8 cavity board?

The masonry standard AS 3700 states “in cavity walls and masonry veneer walls, cavities with a minimum width of 40mm, which are properly detailed and constructed, shall be regarded as being resistant to the passage of moisture”.
Kingspan recommends a maintained 40 mm cavity in all cavity walls to reduce the risk of moisture penetration that can lead to structural damage, poor thermal performance, and health hazards.

What is the difference between Kooltherm & Therma?

Kooltherm is a range of advanced phenolic insulation. It is the thinnest commonly used insulation board for any specific R-value. This means that you can benefit from reduced heating or cooling demand or use thinner boards to gain more space in your building.


Therma is a range of PIR insulation boards.