The Thermal Insulating Properties of Expanded Polystyrene



The world’s fossil fuel sources are depleting at an alarming rate. The majority of the energy is used for heating. Even though fossil fuel resources are diminishing, the world still has sufficient thermal insulation or thermal insulation materials. By evaluating these resources during the construction process based on their thermal insulating properties, heat losses can be reduced, and structure health and comfort can be improved. Individual and national economies will benefit as well by using less energy.

The most important zones for heat loss are outside walls that are not insulated. It will be more beneficial to use the major mass of exterior walls to be insulated inexpensively. Insulating outside walls can avoid 70% of total heat loss. Insulation must be cost-effective and prevent the building’s dead load from increasing. Analyses of Polystyrene materials demonstrate that it is the most cost-effective and lightest in weight among plastic materials for the same thermal conductivity resistance.


The most significant component of insulating material is its performance, which means that it consistently offers the intended barrier to heat passage throughout the building’s lifetime. Other considerations related to the real-life’ installation of the material must be considered part of the design process, even though the insulation manufacturer’s published performance objectives will be an important reference.

Polystyrene-based building products are suitable for many building types and wall systems. As a result, polystyrene, which has a 15% usage ratio in plastics and is a petrochemical product, was chosen. This is due to polystyrene’s excellent insulation and low weight, resulting in a minimal increase in building dead loads. This material has many applications in the construction industry.

In this short read, we shall explore the thermal insulating properties of polystyrene, which influence the material’s performance.


Thermal Conductivity

Thermal conductivity

Thermal Resistance

The Thermal Resistance of a material is calculated by multiplying its Thermal Conductivity by its Width, yielding a number expressed in resistance per unit area (m2K/W). A greater thickness, as well as a poorer conductivity, indicates less heat flow. The sum of these components determines the thermal resistance of the building. A good insulator is a building layer with a high Thermal Resistance; a bad insulator is low Thermal Resistance.

The ratio of Thickness (m) to Conductivity (W/mK) gives Thermal Resistance (m²K/W)

Thermal Diffusivity

The property of the material to allow heat energy compared to its ability to store thermal energy is measured by Thermal Diffusivity. Metals, for example, transport thermal energy quickly (cold to the touch), but wood transmits thermal energy slowly. Thermal Diffusivity is low in insulators. Copper has a velocity of 98.8 mm²/s, while wood has a velocity of 0.082 mm²/s.

Thermal Diffusivity (mm²/s) = Thermal Conductivity / Density x Specific Heat Capacity is the formula.


The density of a material is measured in kg/m³ and relates to its mass (or ‘weight’) per unit volume. A material with a high density maximizes overall weight and has a ‘low’ thermal diffusivity and a ‘high’ thermal mass.

Specific Heat Capacity

The amount of heat energy required to increase the temperature of 1kg of a material by 1K (or 1⁰C) is known as its Specific Heat Capacity. As it needs some time to absorb more heat before it heats (temperature rises) to transfer the heat, a good insulator has a greater Specific Heat Capacity. A property of materials that provide Thermal Mass or Thermal Buffering (Decrement Delay) is their high specific heat capacity.

Vapor permeability

The degree to which a substance allows water to move through it is known as vapor permeability. It is defined as the vapor transmission rate through a unit area of flat material of unit thickness produced by a unit vapor pressure differential between two specific surfaces at a certain temperature and humidity. Vapour permeable and non-vapor permeable insulation are two types of thermal insulation. Walls and roofs referred to as ‘breathing construction’ are defined by their ability to remove vapor from inside the building, lowering the risk of condensation.

Embodied carbon

Though not a part of the insulation’s thermal performance, embodied carbon is important in balancing the global warming gases released during production with those saved during the insulation’s lifetime. Embodied carbon is the number of gases produced from fossil fuels and used to produce energy between the extraction of raw materials, through the production process, and to the factory gates. Of course, it goes much beyond that, including transportation to the worksite, energy use during installation, and deconstruction and disposal. Because the science of embodied carbon is still developing, solid and accurate data is difficult to come by. Look for EPDs that detail the industrial processes’ inputs and outputs.

EPS thermal insulation capability can be assessed with these factors.

  1. Thermal conductivity/ λ (lambda) W / m . K = 0.034–0.038 (18)
  2. Thermal resistance at 100mm K⋅m²/W = 3.52
  3. Specific Heat Capacity J / (kg . K)= 1300
  4. Density kg / m³ = 15 – 30
  5. Embodied energy MJ/kg = 88.60
  6. Vapour permeable: No

EPS is one of the most available materials for building and construction applications to install on the construction site. Get the best polystyrene thermal insulation in UAE by Styrene Insulation Industry (SII), a global supplier.


Our team is happy to answer your questions. Fill out the form and we will be in touch as soon as possible.