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Kingspan Kooltherm K8 Phenolic Cavity Wall Board

High performance Kingspan product, available in most popular thickness’s from the manufacturer, therefore short lead-times apply. This Kooltherm Range includes the following readily available product thickness's 40mm, 50mm, 60mm, and 75mm. Manufactured to order are the following thickness's 20mm, 25mm, 45mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm and 150mm

Product Functions Kingspan Kooltherm K8 partial fill rigid cavity wall insulation

Premium performance cavity wall insulation, K8 phenolic foam boards with low emissivity foil facings are ideal for partial fill cavity walls constructions.

Common applications for this product include …
Cavity Wall (Partial Fill), Single Timber Frame Wall Lining, Steel Stud Frame Walls, Timber Frame Wall Lining, Timber Frame Walls Sheathing

Product Description

The Board Facings

Faced on both sides with a low emissivity composite foil facing which is highly resistant to the transmission of water vapour. This reflective, low emissivity surface can effectively double the thermal resistance of the cavity in which the board is placed.

The Core

The core of K8 is a premium performance CFC/HCFC free rigid phenolic insulant of typical density 35 kg/m3.


K8 is manufactured without the use of CFCs/HCFCs and has zero Ozone Depletion Potential (ODP). 

Compressive Strength

Typically exceeds 100 kPa at 10% compression when tested to BS EN 826: 1996 (Thermal insulating products for building applications. Determination of compression behaviour).

Water Vapour Resistance

Modified to include board facings, the boards achieve a resistance far greater than 100 MN.s/g when tested in accordance with BS 4370–2: 1993 (Methods of test for rigid cellular materials. Methods 7 to 9). 


If correctly applied, K8 Cavity Boards have an indefinite life. Their durability depends on the supporting structure and the conditions of its use.

Resistance to Solvents, Fungi & Rodents

The insulation core is resistant to short–term contact with petrol and with most dilute acids, alkalis and mineral oils. However, it is recommended that any spills be cleaned off fully before the boards are installed. Ensure that safe methods of cleaning are used, as recommended by suppliers of the spilt liquid.

The insulation core is not resistant to some solvent–based adhesive systems, particularly those containing methyl ethyl ketone. Adhesives containing such solvents should not be used in association with this product. Damaged boards or boards that have been in contact with harsh solvents or acids should not be used.

The insulation core and facings used in the manufacture of K8 Cavity Board resist attack by mould and microbial growth and do not provide any food value to vermin.

Product Benefits

Remove any excess mortar and mortar droppings from exposed edges of any installed insulation boards.
Offer the board to the external face of the internal leaf and secure in place using the wall ties and retaining disc / clip.
Ensure wall ties include a retaining disc / clip and be of the double drip type, installed drip downward.

    Premium performance rigid phenolic insulation – thermal conductivity as low as 0.021 W/m.K
    Utilises traditional cavity wall construction methods.
    Clear cavity is maintained – resists moisture penetration.
    Low emissivity foil facings are resistant to the passage of water vapour and double the thermal resistance of the cavity.
    Meets NHBC technical requirements when used with a 50 mm residual cavity.
    Unaffected by air movement.
    Easy to handle and install.
    Non–deleterious material.
    CFC/HCFC free with zero Ozone Depletion Potential (ODP).

Product availability indicators

K8 - Price and Availability Advisory:

Presently there are no availability restrictions, apart from manufacturing lead-times and minimum quantity order levels on the 20mm, 25mm, 45mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm and 150mm boards

Excellent = Product Availability Excellent Good = Product Availability Good Fair = Product Availability Fair Poor =  Product Availability Poor Undetermined = Product Availability Undetermined
Availability relies on stock levels at closest depots and upon transport logistics to effect deliveries

Technical Data

Kingspan K8 Phenolic Insulation Boards for cavity wall applications

Product Code

Board dimensions

Thickness (mm)

λ Value (w/mK)

R-value (m²K/W)

U Value (W/m²K)

Weight (kg/m²)

Unit weight (kg)

Kingspan K8 25 x 0.45 x 1.2 = 13.50m² 20 0.021 0.85 1.18 0.91 12.29
Kingspan K8 20 x 0.45 x 1.2 = 10.80m² 25 0.021 1.15 0.87 1.09 11.77
Kingspan K8 16 x 0.45 x 1.2 = 8.64m² 30 0.021 1.40 0.71 1.26 10.89
Kingspan K8 14 x 0.45 x 1.2 = 7.56m² 35 0.021 1.65 0.61 1.44 10.89
Kingspan K8 12 x 0.45 x 1.2 = 6.48m² 40 0.021 1.90 0.53 1.61 10.43
Kingspan K8 11 x 0.45 x 1.2 = 5.94m² 45 0.020 2.25 0.44 1.79 10.63
Kingspan K8 10 x 0.45 x 1.2 = 5.40m² 50 0.020 2.50 0.40 1.96 10.58
Kingspan K8 8 x 0.45 x 1.2 = 4.32m² 60 0.020 3.00 0.33 2.31 9.98
Kingspan K8 6 x 0.45 x 1.2 = 3.24m² 75 0.020 3.75 0.27 2.84 9.20
Kingspan K8 6 x 0.45 x 1.2 = 3.24m² 80 0.020 4.00 0.25 3.01 9.75
Kingspan K8 4 x 0.45 x 1.2 = 2.16m² 90 0.020 4.50 0.22 3.36 7.26
Kingspan K8 5 x 0.45 x 1.2 = 2.70m² 100 0.020 5.00 0.20 3.71 10.02
Kingspan K8 4 x 0.45 x 1.2 = 2.16m² 120 0.020 6.00 0.17 4.41 9.53

Thermal conductivity / Lambda value (W/mK) = 0.021 - 0.020 | Compressive strength (kPa) = ≥ 100 | Water vapour resistance (MNs/g) = > 100 | Please Note: R-Value = Thermal Resistance; U Value = Thermal Transmittance Co-efficient; Compressive strength = kiloPascals; Vapour resistance = MegaNewton seconds per gram.

Product Information and Certification

Links to manufacturer's information. Click to download in a separate browser window.

Kingspan K8 Datasheet

Kingspan Kooltherm® K8 Range - Certification

K8 Pitched Roof Board insulation is manufactured to the highest standards under a management system certified to BS / I.S. EN ISO 9001: 2008 (Quality management systems. Requirements), BS / I.S. EN ISO 14001 : 2004 (Environmental Management Systems. Requirements) and BS / I.S. OHSAS 18001: 2007 (Health and Safety Management Systems. Requirements).

CE Marking - Kingspan has provided Decelerations of Performance for its products. CE marking is the visible sign, that the product has met the requirements of the European Norms (ENs) and is therefore compliant with the Construction Products Regulation (CPR).

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Product Installation - Kingspan K8

Wall Ties & Retaining Clips

Having applied the clips the outer leaf is then built up to the level of the top of the boards and the process is repeated. Ensure that a residual cavity is maintained in accordance with waterproofing provisions

Kingspan K8 Cavity Boards are normally held in position by the wall ties used to tie the two skins of masonry together, using retaining clips.

Walls are constructed in the conventional manner but with the first run of wall ties at least one course below the damp proof course and at approximately 600 mm horizontal centres.

A section of the inner or outer leaf of the wall is built up to the course below the next run of the wall ties which are situated at a spacing of 450 mm vertically and not exceeding 900 mm (750 mm in Ireland) horizontally.

The K8 board is then placed in position behind the retaining clips on the wall ties, additional wall ties and clips are used to retain the top of the board.

Additional ties may also be required at corners, junctions and cut board ends. Each board should be secured at a minimum of three points. The boards should form a reasonable butt jointed row. The other leaf is then built up to the level of the top of the boards and construction proceeds.

The first row of boards commencing below damp–proof course level also provides some edge insulation to the floor slab.

Successive sections of wall incorporating wall ties and clips are constructed and Kingspan Kooltherm K8 Cavity Board is installed as work proceeds up to the required height.

After raising each section of inner leaf, before installation, excess mortar should be removed and mortar droppings cleaned from exposed edges of the installed slabs.

Use of a cavity batten or cavity board is recommended to protect board edges and maintain a clear cavity.


Cutting should be carried out either by using a fine toothed saw, or by scoring with a sharp knife, snapping the board over a straight edge and then cutting the facing on the other side. Ensure accurate trimming to achieve close butting joints and continuity of insulation.

Daily Working Practice

Installed K8 cavity boards should be protected against inclement weather.

Contact Manufacturer

Kingspan Limited

Kingspan Kooltherm Phenolic Foam, Therma PIR, and Styrozone Polystyrene range of rigid insulation boards

Pembridge, Leominster, Herefordshire, HR6 9LA

Kingspan Technical Advisory Service.

Telephone: 01544 388 601 - Fax: 01544 388 888
Email:  /
Web sites: Kingspan Home Page / Kingspan U-Value Calculator.

Contact us

Insulation Online Limited

Sales Office only:

39 Normandy Road, Worthing, West Sussex, BN14 7DX, UK

Telephone: 0333 8000 828