A couple relaxing in their cosy home in winter

The benefits of good home insulation can’t really be overstated. As expert building material suppliers, the team at Dysart has a lot of experience with both glass wool and polystyrene insulation. In this valuable guide, we take you through the benefits and drawbacks of each of these types of insulation.

A World of Benefits

Before we get onto comparing glass wool and polystyrene insulation, let’s talk about the incredible range of advantages good insulation will bring you.

The most obvious benefit is the money you will save – insulation can reduce your heating and cooling needs by 40%, meaning more affordable power bills. Insulation prevents unwanted moisture entering your home, protecting your furniture, walls, and health. Perhaps most importantly, good insulation makes your house a pleasant place to be, whatever the weather.

Glass Wool or Polystyrene?

With so many benefits, it’s clear that insulating your home is a good idea – but what type of insulation is best for your needs? Here’s a quick run-down of the differences between glass wool and polystyrene insulation.

What Are They?

Glass wool insulation is made by melting recycled glass, quartz sand, and other materials and spinning them into fibres. It can contain up to 80% recycled material.

Polystyrene insulation is a synthetic material made from petrochemical products. It comes as a rigid foam that can be cut into a variety of shapes and thicknesses.

R-Values and Effectiveness

The R-value is a number assigned to insulation to indicate how effective it is at doing its job. Both glass wool and polystyrene insulation types have high R-values and, while polystyrene insulation has a higher average R-value, premium glass wool products outperform even their best polystyrene cousins.

Are They Eco-Friendly?

Both glass wool and polystyrene insulation are reasonably eco-friendly. While the base materials for both are made from non-renewable resources, they also have low toxicity and are produced with a high percentage of recycled materials. Coupled with the emissions saved by using them and both of these insulation products are quite green.

What Are the Best Uses for Each?

Polystyrene insulation is ideal for the ceiling, wall, and underfloor insulation in new homes. It can be retrofitted to homes as well, but only really as under-floor insulation. Wool glass, on the other hand, is well-suited for wall, ceiling, or underfloor applications.

Summing Up – General Pros and Cons

Here’s a quick summary of the pros and cons of these two insulation types. Consider which insulation is best for you:

Glass Wool Insulation


  • High R values, especially in premium range.
  • Low environmental impact with up to 80% recycled material and no toxic contaminants or pollutants.
  • Made in New Zealand.
  • Can be used in both new builds and renovations.


  • Irritating fibres can come loose during installation, so use a mask.
  • Base materials non-renewable.

Polystyrene Insulation


  • High average R value across the range.
  • Can have high recycled content.
  • Stable and long-lasting.
  • Suitable for wall, ceiling, and underfloor insulation in new builds.


  • Vulnerable to damage when exposed.
  • Can shrink over time, potentially causing gaps in your insulation.
  • Toxic if burnt.
  • Only suitable for underfloor insulation in renovations.

If you need help deciding on the best insulation for your needs, try talking to your local building materials supplier.