Where can you use Celotex Insulation Boards? Applications & Benefits Explained

What Applications can I use Celotex Insulation Boards?

Celotex insulation boards are among the most popular choices for builders, contractors, and homeowners looking for high-performance thermal insulation. Known for their lightweight yet rigid structure, these PIR (polyisocyanurate) insulation boards offer excellent thermal resistance, making them ideal for various construction applications.

But where exactly can you use Celotex insulation boards? This guide covers the various applications, from cavity walls to roofing and flooring, helping you understand how Celotex can improve your building's energy efficiency and performance.

Key Takeaways

• Celotex insulation boards are used for walls, roofs, floors, and specialised applications.
• Cavity walls benefit from rigid, full-fill insulation to improve thermal efficiency.*
• Pitched and flat roofs can be insulated using Celotex to reduce heat loss.
• Solid and suspended floors gain better energy efficiency with Celotex insulation.
• Additional applications include garage conversions, garden rooms, and commercial buildings.

1. Wall Insulation Applications

Cavity Wall Insulation

Cavity walls consist of two layers (an inner and outer) with a gap between them. Installing Celotex boards in this space enhances thermal insulation by minimising heat transfer.

Why use Celotex for Cavity Walls?

• Reduces Heat Loss: By filling the cavity with high-performance, rigid insulation, fewer heat escapes, lowering energy bills.
• Prevents Cold Bridging: Celotex boards minimise cold spots in walls, reducing the risk of condensation and mould.
• Space-Saving: Compared to traditional materials, Celotex allows for thinner walls without compromising insulation.

For full-fill cavity wall applications, products like Celotex Thermaclass Cavity Wall 21 are designed to meet strict U-value requirements without needing an additional air gap.

Solid Wall Insulation

Celotex boards can also be used on solid walls, either internally or externally.

Internal Wall Insulation (IWI): Boards are attached to the inside of a property, improving thermal performance without altering the external façade.
External Wall Insulation (EWI): Applied outside the building, reducing thermal bridging and increasing overall insulation.

Best Celotex Product for Walls:

Celotex GA4000 Series – Versatile for internal wall applications.
Celotex XR4000 – Higher thickness options for lower U-values.

2. Roof Insulation Applications

Pitched Roof Insulation

Whether for loft conversions or new builds, Celotex insulation boards are perfect for pitched roofs.

Installation Methods:

• Between Rafters: Insulation is fitted between the wooden beams, leaving ventilation gaps for airflow.
• Over Rafters (Warm Roof System): A continuous insulation layer is installed above the rafters, eliminating cold bridging.

Flat Roof Insulation

Flat roofs are prone to heat loss, making effective insulation critical. Celotex PIR boards are widely used in:

Warm Roof Constructions – Insulation is installed above the waterproof layer, preventing condensation.

Cold Roof Constructions – Boards are placed between or below the joists, requiring additional ventilation.

Best Celotex Product for Roofs:

• Celotex TB4000 – Ideal for tight spaces and rafter applications.
• Celotex FR5000 – Suitable for warm flat roofs due to its superior thermal properties.

3. Floor Insulation Applications

Solid Floor Insulation

Celotex boards can be laid beneath concrete or screed floors to reduce heat loss from the ground up.

Benefits:

• Reduces cold floors in winter.
• Enhances energy efficiency and reduces heating costs.
• Suitable for underfloor heating systems.

Suspended Timber Floor Insulation

For older homes with wooden floors, Celotex boards can be installed between floor joists. This helps:

• Minimise draughts.
• Improve overall thermal performance.
• Prevent heat loss through floor gaps.

Best Celotex Product for Floors:

• Celotex GA4000 – General purpose insulation for floors.
• Celotex XR4000 – Offers thicker insulation for better efficiency.

4. Additional Applications of Celotex Insulation

Garage Conversions
Garages often have poor insulation, making them cold in winter and too hot in summer. Using Celotex on the walls, roof, and floor can turn a garage into a comfortable living space.

Garden Rooms & Extensions
If you're building a garden room or extending your home, using Celotex boards ensures your new space remains warm and energy-efficient.

Commercial & Industrial Applications
Celotex insulation is widely used to meet energy efficiency standards in office buildings and warehouses.

*Please note, recent changes to Building Regulations mean that only non-combustible insulation or insulation of limited combustibility should be used in buildings of over 11 metres in height.  Please refer to the manufacturer's website to check suitability