Comparing Kingspan PIR boards by thickness and declared performance

Changing the lambda alone is not enough, because the manufacturer’s name covers different materials, including PIR Therma and phenolic Kooltherm. The solution should make it possible to identify unambiguously the material suited to the designed function and method of construction. As a starting point for comparing variants, record the full product name, core type, properties document and place of application in the building.

For Therma TR26 the declared lambda is 0.022 W/(m·K), whereas for Therma TR27 the values of this parameter depend on thickness. To compare the two variants, the parameter must be read for the exact thickness selected and the equivalent thermal effect calculated. When comparing polyurethane boards, TR26 and TR27 must therefore be taken into account, as they have different lambdas at the same thickness.

The Kingspan variants being compared should be set against the same required thermal resistance, so that the comparison concerns the same thermal effect. The result must be read with caution, since attributing a lower lambda to the whole brand distorts the parameters of the other product families. The calculation is intended to help verify thermal equivalence at the level of precisely designated offer variants. In the energy summary, show the lambda for the selected thickness, the relevant RD and the consequences of changing the build-up height, so that it is clear what exactly has changed between the solutions.

When comparing a Kingspan offer, it is easy to attribute the lowest lambda found to the whole brand. Such a shortcut leads to the wrong thickness being selected. TR26 and TR27 have different parameters and different facings, and Kooltherm belongs to a different core family. The specific product is identified first. Only then can the required space be calculated and the effect of a material change on the other layers be assessed.

The TR26 facing contains aluminium, while TR27 uses a glass-fibre facing. The two surface types differ in construction and must match the way the layers of the designed roof are joined. In the roof description, check whether the aluminium facing of TR26 has been replaced with the glass-fibre surface of TR27, because continuous polyurethane insulation also requires correct terminations.

When substituting a board, check that the new facing is compatible with the fixing and covering, because losses at joints must be assessed together with the main insulation field. A good joint does not arise automatically, since a common PIR core does not permit substituting the product without assessing the junctions between layers. The layout of elements should allow the function of each junction to be preserved after the material change proposed during construction. On the detail drawing, show the type of surface, the permitted method of joining and the side geometry of both compared boards; this record will make it easier to check the work later.

The Therma insulation board is a different product from a complete sandwich panel with structural facings. The load-bearing function, fixing and execution of the sealing layers must be assigned to the actual solution. When assessing the durability of the thermal effect, take into account the change of insulation product in a cross-section that has separate vapour-control and water-protection layers.

A material change must preserve the continuity of the designed water protection and vapour flow if the insulation is to perform under the conditions assumed in the design. Polyurethane foam does not replace protective layers: a similar board colour does not confirm the same conditions of connection with the membrane or flashing. The intended safeguards should allow the correct protective arrangement to be maintained regardless of the chosen rigid insulation family. Before covering up, assess the description of all layers, the perimeter details and the scope of documentation for the proposed replacement, because later repair may require opening the finished building element.

The material’s reaction to fire and the fire resistance of the partition describe two different properties. Likewise, the compression result at 10% deformation is not a ready design load value. A thickness limitation does not exempt you from checking the other requirements, so analyse the data set covering the material’s reaction to fire, compression and the fire resistance of the entire partition.

Each Kingspan parameter must be attributed to the correct test and scope of application, even when the board’s low lambda was the main reason for its selection. A separate assessment is needed because one favourable board characteristic is not proof that every requirement for the building is met. Only a complete set of data will allow each parameter to be attributed to the correct test and the actual function of the product under consideration. Alongside the thermal results, include the full declaration of the variant and the documentation of the system with regard to load-bearing capacity and fire requirements; this will ensure that the comparison does not omit the service conditions.

An offer for Kingspan insulation should state the full product designation together with its thickness. A substitution proposal is assessed by its effects on the entire system, not merely by the shared PIR designation. Polyurethane insulation in board form should have a calculated effect and scope of works; consider a proposal to replace one Kingspan board with another of a similar name or the same surface colour.

Offers for different Kingspan boards must be compared together with the changes needed in the other layers, so that the cost relates to a single, comparable result. The material price is only part of the decision, since a price difference may arise from a different application rather than from a saving at equal effect. The final comparison should allow the criteria of equivalence to be agreed before purchase approval and amendment of the construction documentation. Ask for the required thermal resistance, geometry, fixing method and the cost of adapting adjacent layers, so that any additional charge has a stated technical justification.