Different areas of a building need different materials, and not all insulation performs the same. In this guide, we break it down into:
- Types of insulation based on where it’s used
- A guide to the main material types
- A simple performance comparison to help you choose what’s right for your project
1) Types of Insulation (By Where It’s Used)
Loft insulation is installed between or over the ceiling joists to reduce heat loss through the roof. Often comes in rolls or loose-fill and is one of the easiest ways to improve a home’s energy efficiency.
Wall Insulation
- Cavity Wall: Fitted in the space between external wall layers using rigid boards or blown-in materials.
- Solid Wall: Either internal (boards fixed to interior walls) or external (rendered boards on the outside).
Floor Insulation
Helps stop heat escaping through the ground floor. Used between joists or as rigid boards laid under screed. Common materials: PIR boards, EPS, XPS, wood fibre
Roof Insulation (pitched or flat)
Placed between or over rafters, sometimes using high-performance boards when space is tight.
Acoustic Insulation
Used inside floors, partitions, and walls to reduce sound transfer - especially in multi-storey homes or flats.
Fire-Rated Insulation
Required in fire-sensitive areas like escape routes or high-rise buildings. Not all insulation is suitable — always check fire ratings. Common materials: Rockwool, slag wool, some phenolic boards
To help you understand where different insulation types are used, and what materials are commonly chosen for each, we've put together the table below:
| Insulation Type | Where It’s Used | Common Materials |
|---|---|---|
| Loft Insulation | Laid between or over ceiling joists to reduce heat loss through the roof. | Mineral wool, Sheep’s wool, Cellulose |
| Wall Insulation | Cavity: Blown-in or boards between wall layers. Solid: Internal or external boards. | PIR, Phenolic foam, Mineral wool, EPS, Natural boards |
| Floor Insulation | Between joists or under screed to reduce heat loss through floors. | PIR boards, EPS, XPS, Wood fibre |
| Roof Insulation | Fitted between or over rafters (pitched or flat roofs). | PIR, Phenolic foam, Mineral wool |
| Acoustic Insulation | Inside floors, partitions, and walls to reduce sound transmission. | Mineral wool, Natural fibres (hemp, wood, cork) |
| Fire-Rated Insulation | Used in fire-sensitive areas like escape routes and high-rises. | Rockwool, Slag wool, Phenolic boards (fire-rated only) |
2) Insulation Materials (By What They’re Made Of)
Mineral Wool
Mineral Wool is a dense, fibrous insulation made from natural rock or slag, offering strong thermal, fire, and acoustic performance. Best for Internal walls, floors, ceilings, soundproofing, and fire-resistant builds.
PIR (Polyisocyanurate) Boards
PIR (Polyisocyanurate) is a rigid foam board known for its excellent thermal performance and slim profile. Best for Fire-rated areas, lofts, partition walls and acoustic insulation
EPS and XPS (Expanded/Extruded Polystyrene)
Lightweight plastic foams, often used below ground. EPS is more breathable; XPS is denser and stronger. Best for floor insulation, perimeter walls, external insulation
Phenolic Foam
One of the most thermally efficient insulations available. It also offers a good level of fire resistance. Best for Space-restricted areas, flat roofs, wall linings
Natural Insulation (Sheep’s Wool, Hemp, Cork, Wood Fibre)
Eco-friendly, breathable, and safe to handle. Performs well in regulating moisture and improving indoor air quality. Best for Eco builds, retrofits, timber frames, internal partitions
Cellulose
Made from recycled paper and treated to be fire-retardant. Blown into lofts and cavities, it’s a great, sustainable option. Best for Loft top-ups, cavity fill in older homes
Performance Table
To help you compare insulation material by thermal, sound, fire, and eco performance, we’ve put together the table below:
| Material | Thermal | Sound | Fire | Eco |
|---|---|---|---|---|
| Mineral Wool | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐☆☆ |
| PIR Board | ⭐⭐⭐⭐⭐ | ⭐☆☆☆☆ | ⭐☆☆☆☆ | ⭐☆☆☆☆ |
| EPS | ⭐⭐☆☆☆ | ⭐☆☆☆☆ | ☆☆☆☆☆ | ⭐☆☆☆☆ |
| XPS | ⭐⭐⭐☆☆ | ⭐☆☆☆☆ | ☆☆☆☆☆ | ⭐☆☆☆☆ |
| Natural (Wool, Hemp) | ⭐⭐⭐☆☆ | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐☆ | ⭐⭐⭐⭐⭐ |
3) Acoustic vs Thermal vs Fire Insulation: What’s the Difference?
Here's a breakdown of acoustic, thermal, and fire insulation, and how they compare to each other.
What is Thermal Insulation?
Thermal insulation's primary function is to keep heat inside during colder months and keep heat outside during warmer months. This helps improve energy efficiency, reduce heating and cooling costs, and maintain a comfortable indoor temperature.
The effectiveness of thermal insulation is measured by its R-value (higher is better for resistance) or U-value (lower is better for heat transfer). Materials like PIR (polyisocyanurate) and phenolic foam are among the top performers, offering excellent thermal resistance even in thin layers ideal for space-conscious designs.
What is Acoustic Insulation?
Acoustic insulation helps reduce unwanted noise between rooms, floors, and ceilings by absorbing sound, and is particularly important in flats, multi-storey homes, or buildings in noisy areas.
There are two main types of sound it helps with:
- Airborne sound, like talking, music, or TV noise. Acoustic insulation helps by adding dense material that blocks or absorbs these sounds before they pass through.
- Impact sound, like footsteps or things being dropped on the floor. To reduce impact noise, insulation is often combined with sound-dampening layers like acoustic mats or resilient layers under flooring.
The performance of acoustic insulation depends a lot on its density. Heavier, denser materials are better at blocking and absorbing sound. Materials like mineral wool and natural fibres (such as hemp or wood fibre) are great options because they can handle both types of sound while being safe and easy to work with.
What is Fire-rated Insulation?
Fire insulation slows the spread of flames, reducing smoke development to help a building maintain its structural integrity during a fire. Unlike thermal or acoustic insulation, fire-rated materials must meet strict safety regulations in rigorous testing and certification for high-risk areas like flats, stairwells, commercial properties, and escape routes.
Note: Not all insulation is fire-safe. Foams like EPS or PUR can be combustible unless treated or protected. Always check for Euroclass A1 or A2 ratings if fire safety is a priority.
Need Help Choosing?
Check out our Choosing the Right Insulation for Your Project guide or get in touch for product advice.