Understanding the Best Cavity Wall Filling for Your Home

Cavity wall insulation is one of the easiest and most effective ways to improve your home’s energy efficiency, cut down on heating bills, and even combat damp issues. But with so many options available, how do you know which cavity wall filling is best for your home? Don't worry, we've got you covered.

This guide will take you through the different types of cavity insulation, their pros and cons, and help you figure out which one is most suitable for your home.

What is Cavity Wall Insulation?

Cavity wall insulation refers to the process of filling the gap between the two layers of a wall with an insulating material. This cavity is present in most homes built after the 1920s and serves as a way to increase the insulation and prevent dampness from entering the property.

By filling this space with insulation, you can drastically improve your home’s energy efficiency. Not only does it keep your home warmer in winter and cooler in summer, but it also helps prevent damp spots and reduces the risk of condensation, so no more battling cold spots or musty smells in your home.

Types of Cavity Wall Insulation

There are a few different cavity wall filling options when it comes to insulation, and each one has its benefits.

1. Mineral Wool

Mineral wool, also known as rock wool, is made from natural minerals such as basalt or slag, and it is available in both batt and loose-fill forms. This type of insulation has been a popular choice for cavity walls for many years, thanks to its excellent thermal and soundproofing properties.

Best For: Older homes or areas where soundproofing is a priority.

Pros:

●     Thermal insulation: Mineral wool provides good thermal resistance, helping to keep your home warm in winter and cool in summer.

●     Soundproofing: It excels at reducing noise, making it a great option for homes in noisy areas or for those looking for enhanced sound insulation.

●     Fire-resistant: As a non-combustible material, mineral wool adds an extra layer of safety to your home, especially in areas where fire safety is important.

●     Breathable: This material allows moisture to escape, which is beneficial for older homes prone to condensation.

Cons:

●     Moisture absorption: If mineral wool gets wet, it can lose its insulating properties, so it's not ideal for homes that suffer from damp unless moisture barriers are also installed.

●     Complex installation: While it provides excellent insulation, mineral wool can be difficult to install correctly. For best results, it's recommended to hire a professional.

2. Expanded Polystyrene (EPS) Beads

EPS beads are small, lightweight balls of expanded polystyrene injected into the cavity wall. These beads bond together once inside the wall, forming a solid insulating layer that helps to reduce heat loss.

Best For: Newer homes or homes where moisture resistance is a priority.

Pros:

●     Moisture resistant: EPS beads don’t absorb moisture, making them ideal for homes with damp problems or those located in areas with high humidity.

●     Thermal efficiency: They offer good thermal performance, making your home more energy-efficient and helping to lower heating bills.

●     Long-lasting: EPS beads are durable and maintain their insulating properties over time.

●     Quick and easy installation: They are relatively easy to install, and a professional can usually complete the job in a short time.

Cons:

●     Not the best for soundproofing: While they do provide thermal insulation, EPS beads are not as effective at reducing noise as materials like mineral wool.

●     Limited breathability: They may restrict airflow in older homes, which can impact the building’s breathability, especially if there are existing damp issues.

3. Rigid Insulation Boards

Rigid insulation boards are solid panels made from materials like expanded polystyrene (EPS), extruded polystyrene (XPS), or polyisocyanurate (PIR). These boards are cut to fit the cavity space and offer high thermal resistance.

Best For: Homes in areas that experience extreme temperatures or where higher thermal performance is needed.

Pros:

●     Superior thermal performance: Rigid insulation boards, especially PIR and XPS, offer excellent thermal insulation, providing high R-values (resistance to heat flow), which improves energy efficiency.

●     Moisture resistant: Some types, particularly XPS, are highly resistant to moisture, making them suitable for homes with damp concerns.

●     Durability: These boards are long-lasting and maintain their insulating properties for years without significant degradation.

●     Great for complex cavities: Rigid boards are ideal for homes with large or irregular cavities, as they can be cut to fit the space precisely.

Cons:

●     Higher cost: Rigid insulation boards, particularly PIR, are more expensive than other materials like EPS beads and mineral wool.

●     Installation complexity: These boards need to be carefully fitted, which requires professional expertise to ensure there are no gaps or errors during installation.

●     Limited flexibility: Rigid boards don’t conform to irregular cavities as easily as other materials, which can be a problem in older homes with more complex wall structures.

4. Cavity Batts

Cavity batts are made from compressed mineral wool, which is then covered with a water-resistant film. These batts are designed to be fitted into the cavity between the inner and outer wall, providing thermal and sound insulation while preventing moisture from affecting the material.

Best For: Homes with standard cavity sizes or those that need extra moisture protection.

Pros:

●     Moisture protection: The water-resistant film helps to prevent the mineral wool from absorbing moisture, ensuring the insulation remains effective and preventing any damp issues.

●     Thermal and acoustic insulation: Cavity batts provide good thermal insulation and also help reduce noise, making them a great choice for homes where both energy efficiency and soundproofing are a priority.

●     Easy installation: These batts are relatively easy to install, especially in homes with standard cavity sizes, and can be fitted by a professional in a shorter time frame than other materials.

Cons:

●     Settling over time: Like other mineral wool products, cavity batts can settle over time, which may reduce their insulating efficiency. This is something to keep in mind when considering long-term performance.

●     Moisture barriers: While the water-resistant film offers protection, it may not be as effective at preventing dampness in areas with high moisture levels compared to other moisture-resistant materials.

5. Spray Foam Insulation

Spray foam insulation is made by mixing polyol resin and isocyanate to create a foam that is sprayed into the cavity. Once applied, the foam expands, filling the space and forming an airtight seal. Although it provides excellent insulation and can fill irregular cavities, there are significant drawbacks to consider.

Best For: Not recommended for cavity insulation due to the following issues.

Pros:

●     Excellent air seal: Spray foam forms a tight seal, which can significantly improve thermal performance and prevent drafts.

●     Custom fit: It expands to fill even the most irregular cavities, making it an ideal option for homes with uneven wall structures.

Cons:

●     Moisture issues: The foam can trap moisture within the cavity, leading to damp problems. This can cause structural damage to the walls and create an environment for mould and mildew to thrive.

●     Settling and degradation: Over time, spray foam can settle, reducing its insulating properties and causing air gaps that undermine its effectiveness.

●     Difficult to remove: Once installed, spray foam is challenging to remove if it causes issues. This makes it a risky choice for cavity wall insulation.

●     Higher installation cost: Spray foam insulation is more expensive to install than other materials and requires a professional with specific expertise.

●     Long-term risks: Given the potential for moisture retention and degradation, we generally do not recommend spray foam as a cavity wall filling.

How to Choose the Best Cavity Wall Insulation for Your Home

When it comes to cavity insulation, there are many cavity wall filling options available, and the best choice for your home depends on various factors, including the type of property you have, the climate you live in, and your energy efficiency goals.

Best Cavity Wall Filling for an Older House

For older homes, polystyrene beads are often the best choice for cavity wall insulation. These beads provide excellent insulation properties and are moisture and mould-resistant, making them ideal for older properties that are more susceptible to condensation and damp issues.

Polystyrene beads are particularly beneficial because they don’t have the same environmental impact as spray foam, while still offering high thermal performance. Unlike mineral wool, which can absorb moisture and become damaged over time, polystyrene beads help keep your home warm and dry, ensuring that your older home stays comfortable without the risks of moisture buildup.

Best Cavity Wall Filling for Newly Built Homes

For newly built homes, mineral fibre (or mineral wool) is the most effective and cost-efficient choice. Newly constructed properties typically have airtight cavities, so the risk of moisture accumulation is minimal, making mineral wool a safe option for insulation.

Not only is mineral wool affordable, but it also offers excellent heat retention, making it a practical and energy-efficient solution. As the cavities in newer properties are generally well-sealed, mineral wool can provide long-lasting insulation without worrying about moisture damage. It's a great option for those seeking a balance between performance and cost.

Looking for Cavity Insulation in Durham or Tyneside?

At North East Insulation Services Ltd, we’re proud to be trusted cavity wall insulation contractors with over a decade of experience in providing energy-efficient home insulation, including cavity insulation, loft and room-in-roof insulation and solid wall insulation.

Get in touch today to find out how we can help you reduce energy bills and enhance the comfort of your home.