Comparing Fibreglass, Cellulose, and Foam Insulation: Pros and Cons

Insulation is a hot topic in the construction world, as energy efficiency becomes increasingly important to the UK’s sustainability goals. More people are looking into insulation for their homes, and many are discovering a swathe of options are available.

There are countless materials and forms of insulation that can be used, depending on the property in question. However, three materials consistently come up in conversation: fibreglass, cellulose, and spray foam insulation.

All of these three methods come in various formats themselves – such as open or closed-cell foam, and batt or loose-fill fibreglass. These variations allow contractors to find the ideal solution for any space, but they also make comparisons tricky.

This blog analyses the general properties seen in common uses of these materials when insulating properties. Before deciding what form of insulation is best for a specific property, it’s worth getting an expert to take a look.

Comparing Fibreglass, Cellulose, and Spray Foam Insulation: An Overview

Fibreglass Insulation

Fibreglass is arguably the most common form of insulation for properties. It is usually made with a combination of glass and plastic fibres and can be used as batts or blown-in loose-fill.

As with many insulation types, most fibreglass insulation is predominantly made from recycled materials.

Fibreglass insulation is popular because it offers a good balance of effectiveness and cost, thanks in part to its great longevity. However, other forms of insulation can perform better in tighter spaces.

Fibreglass Insulation: Pros

• Value – Fibreglass insulation tends to be cheaper compared to Cellulose and Foam.
• Longevity – Compared to other forms, fibreglass can last much longer. If installed as batts, it’s also easy to remove when it needs to be replaced.

Fibreglass Insulation: Cons

• Efficiency – While a good insulator, it has a loser R-value compared to competitors on this list.
• Versatility – Compared to something like foam, fibreglass can be more difficult to fit into awkward spaces and shapes.

Cellulose Insulation

Cellulose is a loose form of insulation commonly made from recycled newspaper treated with chemicals to ensure it’s fire, mould and insect resistant. This material can be hand-placed or blown in.

Cellulose tends to be heavier than fibreglass, which makes it more effective as an insulator. However, it can also lose its performance faster, particularly if subjected to damp conditions.

Cellulose Insulation: Pros

• Performance – Cellulose has a better R-value compared to fibreglass and is particularly useful at thinner densities.
• Versatility – Blown-in cellulose can be particularly useful for insulating hard-to-reach spaces.

Cellulose Insulation: Cons

• Longevity – Cellulose insulation tends to lose performance quicker than other competitors due to its weight (loose-fill can compact over time) and vulnerability to moisture.

Spray Foam Insulation

Foam insulation can come in the form of boards or spray foam. Spray foam in particular is controversial, offering quite striking positives and drawbacks.

Spray foam insulation is commonly sprayed onto a surface, after which it expands to fill the space. This property makes spray foam particularly useful for insulating spaces that are hard to reach or have awkward shapes. However, spray foam also comes with difficulties around price and the potential impact on the property.

Spray Foam Insulation: Pros

• Versatility – Spray foam is a great choice for insulating hard-to-reach spaces or strange shapes where other materials might not be as effective.
• Effectiveness – Spray foam has a great R-value and also excellent soundproofing properties.

Spray Foam Insulation: Cons

• Price – Spray foam insulation can be very costly in comparison to traditional insulation materials like fibreglass.
• Property Impact – Using spray foam can potentially lower the value of a property due to the difficulty of removal.

As mentioned at the top, due to the many variations of each type of insulation, there are no simple best or worst options. Each material here has positives to bring to certain situations, so make sure you consider what might be best for individual uses.