Wall Insulation Board

PF phenolic insulation boards (Phenolic Foam) are the most expensive but also most productive type of insulation boards. They are lightweight but strong thermosetting plastics and are considered to be one of the best rigid, closed-cell structure materials for thermal insulation at present being up to 50% more effective than other common insulation materials such as PIR.  Panels have a slightly higher R-value and a slightly thinner profile than PIR boards due to the manufacturing process. While PIR offers the lambda value of 0.022 W/mK, phenolic closed cell foam offers 0.018W/mK. In fact, that is only 10% better than PIR.Phenolic boards will likely be the most expensive of all the rigid foam insulation options available on the market, however being low thermal conductivity insulation enables high levels of thermal performance to be achieved utilising thinner sections of insulation. The exceptionally low thermal conductivity of closed cell phenolic foam boards means that appropriate insulation efficiency can be achieved with the thinnest possible material.


Phenolic should always be installed above the damp proof membrane (DPM). It is never recommended to lay them exposed directly to the ground. Long term exposure to moisture can result in facings – particularly composite ones featuring kraft paper layers – breaking down, to the detriment of the product. Phenolic insulation is susceptible to decay and causes pipework corrosion when it gets wet. Therefore, measures should be taken to prevent water ingress. Pipework should be properly installed to avoid leaks and all welds should be painted with corrosion resistant paint prior to joint insulation and casing work. Phenolic insulation systems were put in place that the industry realized it creates sulfonic acid when exposed to humidity or direct moisture, like when a roof leaks. In a short time, the acid begins to eat holes in standard painted deck and/or galvanized decks. Phenolic insulation also has a history of crumbling and easily crushes when walked on, leaving a residue on the decking. In order to prevent corrosion in this application, we would need to remove all the residue, which is not practical. But corrosion can’t form without oxygen, moisture and a catalyst. In this case, the catalyst is the Phenolic insulation residue and the sulfonic acid. So the easiest way to prevent corrosion is to use a high-build barrier type coating to stop moisture from contacting the sulfonic residue and steel.


4 main kinds of rigid foam panels you  can choose from - Polyisocyanurate known as Polyiso (PIR), Phenolic foam (PF), Extruded Polystyrene (XPS) - often called Styrofoam - and Expanded Polystyrene (EPS).

Here is their performance comparison: