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EPS For Under Slab Insulation | Slab Insulation Tricks to Improve Home Performance

Rigid foam insulations, such as expanded polystyrene (EPS), have been used successfully under concrete slabs for more than 40 years. Such insulation helps reduce heat loss to the ground in residences, cold storage units, warehouses and other commercial, institutional, cold rooms and industrial structures.

When we think of a home’s insulation, most of us think of walls, floors, and ceilings but, depending on climate, heat loss and gains through uninsulated slabs can make up a significant portion of a home’s heating and cooling load.

The degree to which slabs can be insulated varies widely and so do the energy savings associated with it. Investing the time and money in properly insulating a home’s slab results in many benefits including: energy saving, improved comfort, better moisture control, fewer warranty calls, lower utility costs, and better HERS scores!

Here are a few techniques to help you capture more value.

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Understanding the Benefits of Insulated Slabs

In order to understand why and how to maximize the benefits of insulated slabs, we need to understand how climate and temperature come into play. Ambient temperatures, aka outside air temperature variations, is where it gets tricky.

The greater the temperature difference between the inside and the outside of a home, the quicker heat transfers through a slab. Concrete has the ability to hold or store heat, but it is also more conductive than other building materials such as wood. An uninsulated slab edge will remove heat, or allow heat to enter the home via conduction throughout the year. As a result, priority should be given to insulating exposed slab edges. Best practice for slab insulation depends on the type of slab, and other environmental conditions.

Perimeter insulation is the simplest, most effective way to improve the thermal performance of the concrete slab.


  • Install as a continuous barrier around the edge of the slab.
  • Protect exposed surface with a render finish or a suitable sheet material.
  • Keep finished rendered surface clear of soil. mulch, grass or other natural materials.

Key Benefits

The EPS product, when installed as an under slab construction material, offers builders and installers a number of key benefits including:

  • Quick and easy installation.
  • Lightweight and Safe to handle.
  • Delivers a high and stable R-value.
  • Will not breakdown over time.

Insulation Characteristics

As EPS panel is 97% air by volume, EPS is one of the most efficient man made thermally insulating materials available anywhere in the world. Importantly, the thermal resistance (R value) of the EPS panels remains
consistent over the life of the product due to the rigid cellular structure of the product. Ageing has no effect on the insulation performance
of the EPS panels. As such, EPS insulation products have been used in
residential and commercial building construction in ceilings, walls and floor systems etc, for many years

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