All you need to know on the different types of loft insulation (2025 Update)

Mineral Wool Insulation

If you're considering using your loft for storage or simply want to improve your home's energy efficiency, understanding your insulation options is crucial. Most UK homes have some level of loft insulation already installed—especially newer builds—but whether you're topping it up, replacing old material, or insulating for the first time, it helps to know what’s available.

When most people hear "loft insulation", they picture rolls of thick, fluffy mineral wool packed between joists. While this is indeed the most common type, it’s far from the only option. There are several types of loft insulation to consider, each with distinct characteristics, pros, and cons.

In this guide, we’ll explain the main types of insulation found in UK homes, how they work with raised loft flooring products like Loft Leg and Loft Leg XL, and how to choose the right one for your needs.

1. Quilt, Batt or Blanket Insulation

Best for: General loft insulation, DIY installs, and use with raised loft flooring systems like Loft Leg.

This is the most widely used form of loft insulation in the UK. Supplied in rolls, it is made from mineral wool, glass fibre, rock wool, or natural fibres like sheep’s wool. It’s often found in two layers:

• One layer laid between the joists (typically 100mm)

• Another laid crosswise over the joists (an additional 170mm), to meet the government’s recommended 270mm total depth

  
  

First Layer Of Quilt Insulation Being Installed

This is the insulation type most compatible with Loft Leg raised flooring, allowing you to maintain thermal performance without compression.

✅ Advantages:

• Low cost and easy to source from most DIY retailers

• Simple to install for DIYers

• Can be easily cut to size for fitting around obstructions

• Available in eco-friendly variants (e.g. recycled glass or sheep wool)

• Works seamlessly with Loft Leg and Loft Leg XL to create a stable raised loft floor

  
  

❌ Disadvantages:

• Mineral wool can be itchy and irritating to the skin and lungs (unless using non-irritant natural alternatives like sheep’s wool)

• Bulky to handle and store

• Requires a raised flooring system (like Loft Leg) if you want to board over it

  
  

Perfect Pairing:

If you’re planning to use Loft Legs to raise your loft boards above 270mm insulation, quilt insulation is your best bet. It fits easily around Loft Legs and keeps your home well-insulated.

2. Loose-fill insulation

Best for: Topping up existing insulation or filling gaps around obstructions

Loose-fill insulation is made from granular or lightweight materials such as:

• Recycled cellulose fibre (often made from newspaper)

• Mineral wool pellets

• Expanded cork or perlite granules

  
  

It's typically used for topping up existing insulation in awkward or irregularly shaped spaces where batt insulation is impractical.

✅ Advantages:

• Great for filling gaps, corners or hard-to-reach spots

• Lightweight and easy to pour

• Ideal for topping up existing insulation

• Eco-friendly options available

  
  

❌ Disadvantages:

• Can be dislodged easily by draughts or footfall

• Not ideal in draughty or exposed lofts

• Not suitable for DIY use in most cases—usually needs professional installation

• Can spill or spread into unwanted areas

  
  

Installation Note:

Loose-fill materials can be easily blown around in draughty or ventilated lofts, especially near eaves or soffit vents. Over time, this can lead to:

• Uneven coverage

• Cold spots

• Reduced thermal performance

If you are installing loose-fill insulation consider installing containment barriers to ensure the insulation remains in position.

3. Blown-Fibre Insulation

Best for: Loft areas that are completely inaccessible or filled with obstacles

Loose Fill Insulation Being Installed

Blown-fibre insulation is similar in material to loose-fill but is machine-installed using specialised blowing equipment. It’s typically used in:

• Hard-to-access loft spaces

• Narrow voids or between awkward truss formations

• Properties where lifting flooring or boarding is not feasible

  
  

Materials include treated cellulose fibre, glass wool or mineral wool.

✅ Advantages:

• Fast and efficient for insulating complex areas

• Delivers complete coverage, even in tight or odd-shaped voids

• Provides consistent insulation depth when professionally installed

  
  

❌ Disadvantages:

• Not a DIY option

• May settle over time, reducing effectiveness

• Expensive due to labour and machinery requirements

• Incompatible with standard loft boarding systems

  
  

Top Tip:If you’re planning to board your loft for storage, blown-fibre insulation is not recommended under foot-traffic areas unless you’re using raised platforms like Loft Leg XL to ensure insulation remains undisturbed.

4. Rigid Board or Sheet Insulation

Best for: Loft conversions, spaces with limited headroom, or walls/rafters

Also called sheet insulation, this includes products like Kingspan, Celotex, and other rigid foam insulation boards. They are typically installed between rafters or joists and are often used in loft conversions, or where head height is restricted.

Rigid or Sheet Insulation

Sheet insulation offers excellent thermal performance for its thickness, which makes it great in tight spaces.

✅ Advantages:

• High insulation value per millimetre of thickness

• Fire- and moisture-resistant variants available

• Easy to cut and shape

• Ideal for sloped roofs or wall cavities

• Creates a solid base when finished with chipboard, OSB or plywood

  
  

❌ Disadvantages:

• High material cost

• High environmental cost of production

• Not ideal for laying directly over joists unless combined with structural boards

• Needs precise fitting to prevent thermal bridging

  
  

Good to Know: While effective, sheet insulation isn’t commonly used at loft floor level unless as part of a larger loft conversion project. It’s more suited to insulating loft rafters in a loft conversion than the floor due to the high cost.

Which loft insulation should I choose?

Choosing the right insulation depends on a few key factors:

1. How will you use the loft?

• If you’re using the loft for occasional access or want to keep costs low, quilt or batt insulation is the best fit.

• For hard-to-reach or obstructed lofts, consider loose-fill or blown-fibre.

• If converting the loft into a room, sheet insulation between rafters is usually best.

  
  

2. Do you plan to board the loft?

• For boarded lofts used for storage, raised flooring systems like Loft Leg are essential.

• Never compress insulation under boards. Always maintain the full depth for thermal efficiency.

  
  

3. DIY or professional installation?

• Batt/Quilt insulation is the easiest for DIY installs.

• Loose-fill and blown-fibre require professionals.

• Rigid board insulation is DIY-friendly but requires accurate fitting.

The Role of Loft Leg and Loft Leg XL

Installing loft boards over insulation isn’t safe unless you use a raised system that allows the insulation to stay fully fluffed and effective.

Loft Leg

• Raises boards by 175mm to allow 270mm of insulation (100mm between joists + 170mm over)

• Designed for traditional joist layouts

• Strong and easy to install

• Compatible with P5 chipboard loft panels or sheets

  
  

Loft Leg XL

• Taller at 300mm for extra insulation depth (400mm+)

• Ideal for new builds with trussed roofs

• Helps maintain NHBC warranty compliance

• Distributes weight evenly across larger joist spacing

Learn more: Loft Leg Product Page

Frequently Asked Questions

Can I put boards directly on top of insulation?

No. Doing so will compress the insulation and reduce its performance. Always use raised supports like Loft Leg.

Is 270mm of insulation really necessary?

Yes. 270mm is the recommended depth in the UK to meet modern energy efficiency standards and reduce heating costs.

Can I use Loft Leg with any type of insulation?

Loft Leg works best with batt or quilt insulation. It’s not designed for use with loose-fill or blown insulation unless that insulation is contained and not displaced.

Will boarding over insulation void my warranty?

It can—if you compress the insulation or affect the roof’s ventilation. Raised systems like Loft Leg XL are designed to preserve compliance.

Final Thoughts

Choosing the right type of loft insulation isn't just about energy savings—it's also about protecting your home from damp, ensuring proper airflow, and even staying within the conditions of your home warranty. Whatever insulation type you choose, remember:

• Don’t compress insulation under loft boards

• Use raised loft flooring systems to preserve thermal performance

• Maintain airflow and avoid covering eaves or vents

  
  

If you're planning to install loft boards over insulation, make sure to use a system like Loft Leg or Loft Leg XL to create a safe, stable, and energy-efficient loft space.

Explore Further:

• Shop Loft Leg Products

• How to Install Loft Boards Without Damaging Your Insulation

• NHBC Guidance on Loft Boarding

Feel free to browse our products right here on our site, or alternatively give us a call on 01282 861 001.