With the wide range of insulation materials available, it can be tiresome determining which material is best suited in which application. InsulShop is here to help! For this article, we venture into the petrochemical insulation materials used very frequently in the mechanical market: Expanded Polystyrene (EPS) and Cross-Linked Polyethylene (XLPE). So, what are the differences and where do each of them find their optimal application?

First, a bit of background on the materials:

Polystyrene is the polymer of the monomer Styrene and can be found in both a solid, as well as a foam state. To get the foam state, one would need to add CO2 as a blowing agent. It has a relatively low melting point and starts to change at around 100°C. These traits can be found in all PS products without any additional additives, but we will be focussing on the foam state from here on.    

EPS is rigid, and although a little messy, is still relatively easy to work with. The major drawback is that EPS cannot provide an inherent material vapour barrier. The product has an open cell structure, meaning that air can move freely within the material. As a result, the insulation value (depending on the density and grade) is considered good, to very good. It is important to note that Polystyrene is susceptible to degradation and the thermal conductivity can change over time, worsening the insulation value. However, the new NCC 2019 addresses this problem with new and improved thermal conductivity testing.

Moving on to the XLPE. Cross-Linked Polyethylene starts off as a ‘Low Density Polyethylene’ granules, also known as LDPE. Under heat and a foaming agent, these granules expand into a foam. The Cross-Linked part of the name, means that the polyethylene polymers have links between them, resulting in stronger bonds between the chains. This in turn provides better shear strength, higher temperature resistance and a more rigid material. The foam is a closed cell foam, meaning that each cell is its own pocket and air cannot freely move though the material. Our Flexicell XLPE also has a flame laminated foil facing over the top, which provides additional vapour security as well as a high energy taping surface.

Contractors often find a large overlap within the uses of these materials and it is often hard to determine which is more suitable on a job based off the application. Both products have a similar thermal limitation. Neither cope well with high temperatures, however, the upper limit for XLPE is slightly higher for Flexicell at 105°C and only 90°C for EPS, making XLPE more suitable for hot water applications. The vapour barrier, inherent in XLPE due to its closed cell structure, also makes it the preferred material for cold water applications. Especially where there is high chance for mechanical damage.

So, EPS is a great insulator, but where does it fit in to the mechanical market if XLPE is better for both warm and cold applications?

There are a couple of characteristics that keep Expanded Polystyrene in the market. It has accurate tolerances, flexibility in shapes and sizes and a very low-cost production process. EPS is cut from block, which means there is less guess work in the final dimensions of the product. This production method also offers flexibility in shapes and sizes, making it very suited for one-off projects, specials and bespoke applications.

EPS from InsulShop, comes with a Z-lock shape at the seams, for additional gluing surface and easy aligning. The rigidity of the material can also be of benefit, as it allows for an incredibly neat and clean finish. The primary benefit EPS has over XLPE is the purchase price. EPS is significantly cheaper per metre (material price) than XLPE. This is mainly because Expanded Polystyrene is one of the worlds most produced plastics, with several million tonnes every year. It is also produced locally, which dramatically reduces the secondary costs associated for a distributor, including freight, storage and logistics.

In saying this, we understand that material cost, while very important, is still only one aspect of a project and so the cheaper material cost comes with a warning. Due to its rigidity and stiffness, the on-site installation time tends to be longer, incurring more labour cost.

After reading all this, I bet you’re eager to know where we stand on the issue! In our opinion, XLPE is a cheaper product to use in the long run. It has greater thermal efficiency and is overall quicker and easier to install onsite. As an added benefit, the better insulation value means that you are able to use thinner wall thicknesses to assume the same R-Value requirements. However, if you are stuck with a bespoke project of an unusual size with a short timeline and small budget, then polystyrene is the winning choice.

In saying this, every job is different, and every project will have a specification and a budget. Although both materials have their benefits and drawbacks, both have their uses and will continue to be part of InsulShop’s product offering.