Should I insulate my concrete slab?

July 20, 2023

Insulating a concrete house slab offers several significant benefits, particularly in terms of energy efficiency, comfort, and cost savings. 

But of course everything comes at an initial cost, so is it worth it?

There are a few research papers on this in Australia with the most relevant to us being one done on Victorian and Tasmanian homes.

To break it down here are the key take away points found.

  • Going from no insulation to the most common minimum (40 mm thick polystyrene foam board) had a much larger impact then from 40mm to 80mm foam showing that something is a lot better then nothing, but you don’t get as much return for going overboard.
  • The biggest heat loss in a concrete slab is through the sides that are above ground level. There is still heat loss through the ground, but it’s much greater where there is free air flow. So first priority is to insulate the sides, and then if the budget allows, the bottom of the pads which have a large surface area and the thinnest cross section of concrete (usually 100-150mm) and lastly the slab beams.
  • The greater the temperature difference from your slab to the ground or outside air temperature the greater the loss. So if you’re heating your slab with an in slab hydronic system, there’s a much better return on your investment by insulating your slab.
  • If you’re not heating your slab directly, it will still gain warmth through the heating of the inside air, but it will sit at a temperature somewhere between the inside and outside temperatures. So this small difference from slab to out side temp means less loss and a lower return on your investment by insulating your slab.
  • Polished concrete floors. If you’re going to have polished concrete floors then retaining heat in the floor is much more beneficial both for comfort under foot and efficiency. 
  • Covered floor. If you’re going to have floor coverings like timber, carpet or engineered flooring boards, under slab insulation can be substituted with insulating between the concrete and the floor covering.

Here are some of the other key considerations and advantages of concrete slab insulation:

  • Improved Energy Efficiency: Insulating the concrete slab helps in reducing heat loss during colder months and prevents heat gain during warmer months. This means that your home will require less energy for heating and cooling, leading to lower utility bills and a smaller carbon footprint.
  • Enhanced Thermal Comfort: Insulation regulates the temperature of the interior space, creating a more comfortable living environment. A well-insulated slab prevents cold floors during winter, providing a cozy feeling underfoot and reducing the need for extra heating.
  • Long-Term Cost Savings: Though insulating a concrete slab adds an initial cost to the construction or retrofitting process, it can lead to long-term savings through reduced energy consumption. Lower heating and cooling bills can quickly offset the upfront expenses of insulation.
  • Durability and Protection: Insulation helps protect the concrete slab from temperature fluctuations and potential moisture-related damage, which can extend the lifespan of the structure.
  • Health Benefits: Proper insulation reduces the likelihood of moisture and mold growth, which can improve indoor air quality and contribute to a healthier living environment for occupants.
  • Environmental Impact: By reducing energy consumption and greenhouse gas emissions, insulated concrete slabs contribute to a more sustainable and environmentally friendly living space.
  • Increased Property Value: Energy-efficient features, including insulated slabs, are becoming increasingly desirable to homebuyers. Insulation can enhance the resale value of a property and attract more potential buyers.

It’s important to note that the effectiveness of insulation depends on the choice of insulation material, installation quality, and the overall building design. Properly insulating a concrete slab should be done in conjunction with other energy-efficient measures in the house, such as insulated walls, windows, and roofs, to maximise the benefits and create a truly energy-efficient and comfortable living space.

We are a local building and carpentry business based in Point Lonsdale, servicing the Bellarine Peninsula.

We have over a decade’s experience in a wide range of construction, from high quality architectural new builds to creative and practical renovations extensions and restorations.