The Ultimate Guide To Insulation

This guide breaks down everything you need to know about insulation, from the different types available and where they can be used, to fire safety, environmental impact, and compliance with building regulations.

We’ve kept things practical and easy to follow, so whether you’re a homeowner or a trade professional, you’ll come away with the clarity you need to make confident decisions.

Use the links below to skip to the section most relevant to you:

• What is Insulation?
• How Does Insulation Work?
• Types of Insulation Materials
• Choosing the Right Insulation
• Fire, Sound & Thermal Performance
• Installation Basics
• Building Regs & Compliance
• Environmental Considerations

Insulation is a type of material used in a building to help control temperature and improve energy efficiency. It’s typically installed in walls, floors, roofs, and lofts, and depending on the material used, it helps with noise reduction and fire resistance.

Beyond comfort, insulation plays a key role in lowering running costs and boosting a building’s overall performance. In many cases, it’s also a legal requirement to meet modern building standards or improve energy ratings.

Insulation comes in many forms, from rigid PIR boards to loose-fill products and natural alternatives, each suited to specific parts of a building and different performance needs.

It can save homeowners up to £540 a year on energy bills, depending on the property’s size and current insulation levels.

As the Energy Saving Trust puts it: “Installing insulation or draught-proofing helps reduce heat loss, cut energy bills, and lower carbon emissions.”

For more on energy-saving solutions, visit  Energy Saving Trust: Reducing Home Heat Loss.

Insulation works by resisting the natural flow of heat through a building’s structure. Heat moves from warm to cooler areas, whether that's indoor warmth escaping on a cold day or outdoor heat trying to enter during the summer. Insulation slows that process down.

Insulation can also work differently depending on the material and where you use it to get the best performance out of your home or building. Some types trap small pockets of air to slow down heat escaping, others reflect heat away, and some are just so dense that heat has a harder time passing through. All of this helps keep the temperature inside your home more stable. 

The performance of insulation is usually measured by its R-value - the higher the R-value, the greater its resistance to heat flow.

There are several types of insulation materials used in buildings today. Each has its own strengths depending on where it’s used, the budget, and specific performance needs like fire resistance, soundproofing, or sustainability. 

If you're unsure where to begin, check out our guide to insulation materials for a deeper breakdown.

Here are the most common insulation types used in homes and buildings:

• Fiberglass is one of the most widely used insulation materials. Made from fine strands of glass, it’s affordable, easy to install, and effective for both heat and sound insulation.
• Mineral wool includes rock wool (also called stone wool) and slag wool. It’s made from natural rock or industrial waste and is known for its fire resistance and sound-blocking properties.
• Cellulose is a loose-fill insulation often used in walls and attics. Made from recycled paper, it’s treated to resist fire and pests and is a good, eco-friendly option.
• PIR (Polyisocyanurate) is a type of rigid foam board insulation. It offers high thermal performance and better fire resistance than some other foam boards. It’s commonly used in flat roofs and walls.
• Phenolic insulation is a rigid board known for its excellent fire and smoke resistance. It performs well in tight spaces and offers good thermal values with a thinner profile.
• Natural Fibers are made from renewable materials and are often used in eco-conscious construction. Common types include sheep’s wool, cotton (recycled denim), hemp, and wood fiber. They’re breathable, non-toxic, and offer decent thermal and acoustic performance.
• Polystyrene is available in two main types: EPS (Expanded Polystyrene) is lightweight and commonly used in walls and floors, and XPS (Extruded Polystyrene) is stronger and more resistant to moisture than EPS.
• Aerogel is a high-performance insulation that’s extremely lightweight with very low thermal conductivity. It’s mainly used in specialist applications due to its high cost.
• Vacuum Insulated Panels (VIPs) are thin, flat panels with vacuum-sealed cores that offer excellent insulation in a compact form. They’re fragile and expensive but useful where space is limited.

The right choice depends on where it’s going, the kind of performance you need (thermal, acoustic, fire-resistant), and how the space is built. Below is a breakdown of common areas in a home and the best types of insulation for each.

The best choice depends on what part of the building you’re working on and what matters most: warmth, soundproofing, fire safety, or energy savings. For example:

• Floors benefit from rigid boards or mineral wool between joists.
• Walls vary between cavity fill, external cladding, or internal boards.
• Roofs and lofts typically use PIR boards or mineral wool rolls, depending on whether the space is used.

For a detailed breakdown by floor, wall, roof and building type (new build, old home, commercial), check out our full guide: How to Choose the Right Insulation for Your Project.

Proper storage and handling on site are essential to maintain its performance and lifespan. Read our expert guide on how to store and handle insulation safely.

Insulation doesn’t just keep a building warm, it also plays a role in fire safety and sound control. Some insulation materials offer strong fire performance, meaning they are fire-rated and resist burning. Others are combustible and should not be used in fire-sensitive areas without protection. Understand the difference:

• Fire protection slows fire spread.
• Fire-stopping seals gaps to prevent fire and smoke from moving through a building.

High-risk areas like external walls and high-rise buildings often require non-combustible materials, so always check the product's fire rating and match it to building regulations.

Sound Performance relates to noise control and uses insulation designed for sound absorption:

• Mineral wool and natural fibers perform well between walls, floors, and ceilings.
• Foam boards are not effective on their own for sound.

See our Wall, Floor & Ceiling Soundproofing Tables for detailed material strategies.  

Thermal Performance is about heat retention and energy efficiency:

• PIR, phenolic, and spray foam offer strong thermal performance in thinner layers.
• Mineral wool, fiberglass, and natural options may need more thickness but are reliable and breathable.

Choose insulation that matches the performance needs of your project (fire, sound, thermal) and always check for compliance with local codes.

Installing insulation may seem straightforward, but there are important things to consider to make sure the job is done properly, safely, and efficiently.

Whether you’re doing it yourself or hiring professionals, here’s what you need to know: (For a more step-by-step breakdown by Floor, Wall and Roof - including tools, safety tips, and best practices - check out our Beginner’s Guide to Installing Insulation. It’s also worth reviewing the most common insulation mistakes to avoid, so you don’t lose performance when installing Insulation).

1.  Before you start, make sure you order enough insulation for your entire project:

• Calculate the quantity you’ll need based on area measurements and thickness.
• Order in advance to account for delivery times, especially if you're working on a tight schedule. Some materials may have longer lead times, depending on availability.

2. When you receive your insulation, be sure to:

• Inspect the packaging for damage. If you see any, notify the supplier immediately.
• Check the quantities to ensure everything you ordered has arrived.
• Store insulation properly. Keep it dry, as some materials (especially natural fibers and cellulose) can absorb moisture and lose effectiveness.

3. Self-Installation vs Hiring a Professional

Deciding whether to install insulation yourself or hire a pro depends on the complexity of the job, your experience, and the type of insulation being used.

• DIY Installation: Many types of insulation, such as fiberglass or mineral wool, are easy to install yourself if you follow the instructions. Just be sure to wear protective clothing (gloves, mask, goggles) and ensure you’re working in a well-ventilated space.
• Professional Installation: For more complex jobs (like spray foam, blown-in insulation, or installing insulation in tight spaces), it’s often worth hiring a professional. They’ll ensure the job is done safely and according to local building codes, plus you won’t have to deal with the mess or the learning curve.

4. Recommended Accessories and Tools

Whether you’re going DIY or hiring pros, having the right tools and accessories will make the installation process easier and more effective.

• Measuring Tape and Scissors: Essential for cutting insulation to the correct size.
• Utility Knife: For cutting batt or roll insulation quickly and accurately.
• Staples or Adhesive: Use these to secure batt insulation to walls or other surfaces if needed.
• Gloves, Dust Mask, and Goggles: For safety, especially when working with fiberglass or cellulose insulation.
• Knee Pads: If you’re installing in attics or ceilings, knee pads can provide comfort during long hours of work.

5. General Installation Tips

• Ensure a tight fit: Gaps between insulation pieces can reduce thermal and acoustic performance.
• Don’t compress insulation: Compressing materials like fiberglass or cellulose reduces their effectiveness. Make sure the insulation is installed at the recommended thickness.
• Consider air sealing: Before installing insulation, check for air leaks and seal them. Insulation works best when combined with proper air sealing.

Building regulations vary by country and region, but there are common standards that must be adhered to in terms of fire safety, thermal performance, and structural integrity. Make sure you’re familiar with these before starting your project.

Key points to consider:

• Thermal Performance: Insulation must meet certain U-values or R-values to ensure energy efficiency.
• Fire Safety: Fire-rated materials are required in certain locations, such as between floors or in external walls, to prevent the spread of fire.
• Ventilation: Proper ventilation must be maintained to prevent issues like damp or mold, particularly when installing insulation in lofts and walls.
• Moisture Protection: Some insulation materials are more resistant to moisture than others. Consider this when working in high-humidity areas, such as basements or external walls.

Ensure the insulation you use is certified and approved for the intended application. Look for relevant marks or certifications, such as:

• CE Marking for products sold in the EU.
• BSI Kitemark for quality assurance.
• Fire Safety Ratings to meet specific building codes.

Various governing bodies oversee building regulations, and their websites offer up-to-date information and guidance. These include:UK Building Regulations (gov.uk) Visit the official UK government website for building regulations

As the building industry moves toward greener standards, the environmental impact of insulation is becoming more important. More homeowners and building professionals are now looking at how products are made, how long they last, and how easy they are to recycle at the end of their life.

New eco-friendly materials are being developed to improve sustainability without compromising performance. These include options made from recycled content, natural fibres, and low-emission manufacturing processes.

The Green Guide rating, developed by BRE (Building Research Establishment), helps assess how environmentally friendly a building material is across its full lifecycle. Products are graded from A+ to E based on their environmental impact. This can be a useful tool when choosing insulation for sustainable projects or working toward environmental certifications.

For a deeper breakdown of material impacts, recyclable options, and how to make greener choices, read our full guide on the Environmental Impact of Insulation Materials.

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