Best Insulation Materials for Loft and Roof Spaces in 2025

When it comes to improving energy efficiency, reducing heating bills, and creating comfortable living spaces, loft and roof insulation is one of the smartest investments a homeowner can make. Whether you’re planning a loft conversion or upgrading your existing roof insulation, choosing the right materials is essential for performance, cost-effectiveness, and sustainability.

Here are the best insulation materials for lofts and roof spaces in 2025, along with their benefits and ideal applications.

 1. Mineral Wool (Rock Wool / Glass Wool)

Best for: Between joists, sloped roofs, and general loft insulation

Mineral wool is one of the most popular roof insulation choices due to its thermal efficiency and affordability.

Benefits:

• Excellent heat retention

• Fire-resistant

• Great sound insulation

• Easy to install in rolls or slabs

It’s particularly effective for older properties and traditional loft layouts.

 2. PIR Boards (Rigid Foam Insulation)

Best for: Loft conversions, dormer roofs, flat roofs, and tight spaces

Polyisocyanurate (PIR) boards like Celotex or Kingspan are ideal when space is limited but high insulation performance is needed.

Benefits:

• High thermal efficiency

• Slim but powerful insulation

• Easy to cut and fit between rafters

• Great for habitable lofts

Perfect for converting roof spaces into bedrooms, offices, or en-suites.

 3. Sheep Wool Insulation

Best for: Eco-friendly homes, breathable roofs, and period properties

A natural and sustainable material that’s gaining popularity in green home renovations.

Benefits:

• Non-toxic and biodegradable

• Regulates moisture naturally

• Excellent thermal and acoustic insulation

• Long-lasting and comfortable to work with

Ideal for homes looking for chemical-free, natural insulation options.

 4. Spray Foam Insulation (Open or Closed Cell)

Best for: Hard-to-reach roof spaces, dormers, trussed rafters, and conversions

Spray foam expands to fill every gap, creating an airtight seal.

Benefits:

• High insulation performance

• Prevents air leaks and drafts

• Adds structural stability

• Compatible with most loft designs

Closed-cell foam is dense and moisture-resistant, while open-cell foam is breathable and ideal for conversions.

 5. Multifoil Insulation

Best for: Loft conversions, roof overlays, and tight roof spaces

Multifoil insulation combines reflective layers with thermal padding, offering great performance with minimal thickness.

Benefits:

• Slim design — ideal for low headroom areas

• Reflects heat effectively

• Lightweight and easy to install

• Works with other insulation types

Often used as an additional layer in warm roof construction.

 6. Cellulose Insulation (Recycled Paper)

Best for: Sustainable upgrades and older homes with irregular roof spaces

Made from recycled newspaper treated for fire resistance.

Benefits:

• Environmentally friendly

• Good thermal and acoustic performance

• Great for filling awkward areas

• Cost-effective and efficient

Blown-in cellulose is ideal for topping up existing insulation.

 7. Wood Fibre Insulation Boards

Best for: Eco homes, pitched roofs, and breathable walls

A growing trend in sustainable construction, especially for loft conversions with a natural finish.

Benefits:

• Breathable and vapour-regulating

• Great thermal mass

• Made from renewable materials

• Ideal for timber-frame homes

Often used alongside natural plasterboard or interior cladding.

 Warm Roof vs Cold Roof Insulation

Warm Roof:
Insulation is installed above or between the rafters — ideal for loft conversions and habitable spaces.

Cold Roof:
Insulation is installed between the ceiling joists — best for storage lofts or unoccupied roof spaces.

Your insulation choice depends on how the loft will be used.Why Loft Insulation Matters

Choosing the right material offers long-term benefits:

✔ Reduced heating bills
✔ Increased property value
✔ Better comfort in all seasons
✔ Compliance with new energy standards
✔ Eco-friendly home improvements

 Need Professional Loft Insulation or Conversion?

Whether you’re upgrading existing insulation or converting your loft into a functional living space, professional installation ensures long-term performance and compliance with building regulations.