Understanding the Different Types of Wall Insulation for Your Home

Miclan Kerr
Dec 15, 2025
3 min read

Keeping your home comfortable and energy-efficient starts with good insulation. Walls play a crucial role in maintaining indoor temperature, reducing energy bills, and improving overall comfort. Choosing the right type of wall insulation can make a big difference in how well your home retains heat in winter and stays cool in summer. This guide explains the main types of wall insulation, how they work, and what to consider when selecting the best option for your home.

Why Wall Insulation Matters

Walls are one of the largest surfaces through which heat can escape or enter a house. Without proper insulation, your heating and cooling systems have to work harder, leading to higher energy costs. Good insulation also reduces noise from outside and helps prevent moisture problems that can damage your walls.

Understanding the different insulation types helps you make informed decisions that fit your budget, climate, and home structure.

Types of Wall Insulation

Wall insulation generally falls into three categories: cavity wall insulation, solid wall insulation, and internal or external wall insulation. Each type suits different building styles and offers unique benefits.

Cavity Wall Insulation

Many modern homes have cavity walls, which means there is a gap between two layers of brick or block. This gap can be filled with insulating material to reduce heat loss.

Common materials used:

Mineral wool
Fiberglass batts
Cellulose
Foam insulation

Advantages:

Relatively easy and quick to install by injecting insulation into the cavity
Improves energy efficiency significantly in homes with cavity walls
Cost-effective compared to other insulation types

Considerations:

Not suitable for homes with very narrow or blocked cavities
Requires a professional assessment to check cavity condition before installation

Solid Wall Insulation

Older homes often have solid walls without a cavity. Insulating these walls requires adding insulation either on the inside or outside surface.

Internal Wall Insulation

This involves fixing insulation boards or stud walls filled with insulating material to the inside of external walls.

Pros:

Can be installed room by room
Less expensive than external insulation
Improves thermal comfort

Cons:

Reduces internal space slightly
May require redecorating after installation
Can cause condensation if not properly ventilated

External Wall Insulation

This method adds insulation material to the outside of the walls, covered with a protective render or cladding.

Pros:

Improves wall strength and weather resistance
Does not reduce internal space
Can improve the appearance of the home

Cons:

Higher upfront cost
Requires planning permission in some areas
Installation takes longer and may disrupt outdoor spaces

Other Insulation Materials and Methods

Besides the main types, there are various materials and techniques to consider:

Spray foam insulation: Expands to fill gaps and cracks, providing excellent air sealing. Suitable for cavity walls and hard-to-reach areas.
Rigid foam boards: Used in both internal and external insulation, offering high thermal resistance.
Natural insulation materials: Such as sheep’s wool, cellulose, or hemp, which are eco-friendly and breathable.

How to Choose the Right Wall Insulation

Selecting the best insulation depends on several factors:

Type of wall construction: Check if your walls are cavity or solid.
Climate: Colder regions benefit more from thicker insulation.
Budget: Consider installation and long-term energy savings.
Space: Internal insulation reduces room size; external preserves it.
Moisture control: Proper ventilation and damp-proofing are essential.
Building regulations: Some insulation types may require permits or meet specific standards.