Home Improvement

If polystyrene insulation works for fridges, it should work for a house, right?


Polystyrene. You may know it as “Styrofoam” or the thing that helps keep fridges cold. But what is it really? And can you use it to insulate your house? 

Whether you’re building a new home or about to embark on some renovations, thinking carefully about your insulation can make a big difference in the long run. Afterall, insulation is the best way to help you regulate temperatures inside your home and can significantly decrease your energy consumption when it’s done right.

Read on to find out what polystyrene insulation is, whether it’s a good choice for your home and how it stacks up compared to other options. 

What is polystyrene anyway?

Polystyrene is a type of plastic, one of the most widely used today. You’ll find it in toys, electronics, packaging and more. Polystyrene can be expanded into a foam like material that contains millions of tiny air pockets inside its structure. This expanded form of polystyrene is used to create insulation products such as expanded polystyrene (EPS) and extruded polystyrene (XPS) insulation.

What makes polystyrene a good thermal insulator?

Air is one of the best insulators out there. Polystyrene foam, like every other type of bulk insulation, contains millions of tiny air pockets in its structure. This breaks up the flow of heat, helping you prevent heat loss and gain. Add on the fact that polystyrene itself is a poor conductor of heat and you’ve got an effective thermal insulator. 

Some polystyrene products are manufactured with a thin foil layer on one or both sides. Since the foil layer is reflective, it will reflect radiant heat and help keep your home warmer in winter and cooler in summer. 

Can you insulate your home with polystyrene?

Polystyrene foam insulation can be used in both residential and commercial applications. One common use for it in new homes is to install it below the foundational concrete slab. This will help reduce heat loss and gain through the ground when ground level temperatures fluctuate. Polystyrene insulation can also be installed in flat roofs, ceilings, cool rooms and cavity walls. 

How does polystyrene measure up to the other insulation options?

Polystyrene is just one type of insulation you can use in your home – there are a huge range of other products available. Below we take a look at where polystyrene shines and where it falls short compared to other popular insulation materials like glasswool and polyester batts.

Thermal performance

Polystyrene foam provides great thermal resistance, as do glasswool and polyester. When looking for a higher performing product, it’s most important to look at the R-Value of the product. The R-Value indicates how effective it is at resisting heat loss and gain. Polystyrene, glasswool and polyester all come in a range of R-Values to suit different applications. Check the local guidelines for appropriate R-Values based on where you live.

Moisture resistance

Polystyrene insulation has excellent moisture resistance because of its compact structure. This means moisture cannot penetrate and issues like mould and compression due to moisture are not a big issue with polystyrene. When installing glasswool and polyester batts, it’s important that the area is dry and that there is enough ventilation as moisture build up can cause mould issues or compromise the performance of the batts.

Compressive strength

Polystyrene foam insulation has high compressive strength if it is a closed cell type like extruded polystyrene (XPS) or expanded polystyrene (EPS). This means these types of insulation can withstand compression better, making them highly durable. Open cell types of foam insulation are springier and compress more easily which can compromise their performance. Glasswool and polyester batts can also be compressed with pressure or if they are wet, and care should be taken during installation to ensure that they are not compressed.

Ease of handling

Polystyrene foam insulation is easy to handle and cut, and normally comes in large sheets or rolls. It has no loose fibres in its structure which means it won’t cause itchiness or irritation to the skin as traditional glasswool is known for. Nowadays, glasswool products like Earthwool insulation are manufactured with highly advanced processes which make them soft to touch with virtually none of the itch factor. Polyester batts are also easy to handle.

Acoustic performance

Polystyrene does not have great soundproofing properties on its own because it lacks the density and thickness. However, when paired with other materials, such as structural insulated panels (SIPs) its soundproofing ability greatly improves. Glasswool and polyester batts have good acoustic properties. Installing any glasswool or polyester batt will have some acoustic benefits but investing in specialised sound insulation options will get you the best results when installed in walls and between floors of multistorey homes.

Environmental impact

While all types of home insulation can help reduce your home’s energy consumption, some are kinder on the environment than others. Polystyrene is not easily recycled and there are no biological agents that can break it down, so a lot of it ends up in landfill. The process of creating polystyrene emits harmful chemicals into the atmosphere and relies on petroleum which is a non-renewable resource. 

Glasswool is made from recycled glass materials and sand, which is an abundant resource. Polyester is made from recycled plastic materials such as plastic bottles and bags. At the end of their lives, both glasswool and polyester can be recycled. If you are looking for a more eco-friendly insulation option, check out the environmental policies of different manufacturers. Knauf Earthwool, for example, uses a bio-based binder instead of petroleum-based chemicals and doesn’t contain any phenol or formaldehyde.

Ready to insulate your home?

Whether you choose to use polystyrene, glasswool, polyester or a combination of different materials, insulating your home is one of the best things you can do to reduce energy consumption and save on electricity bills. You’ll be much more comfy year round with insulation in your walls, ceiling and floors!

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