Metal roofs are becoming increasingly popular due to their durability, longevity, and energy efficiency. However, without proper insulation, the full potential of a metal roof may not be realised. Insulation plays a vital role in maintaining a comfortable indoor environment, reducing energy consumption, controlling condensation, and minimising noise transmission. In this comprehensive guide, we will explore the importance of metal roof insulation and discuss different types of insulation materials to help you choose the best option for your property.

Types of Metal Roof Insulation Materials

Several insulation materials are suitable for metal roofs, each with its own advantages and considerations. Here, we will discuss the three most common types of metal roof insulation materials: spray foam insulation, rigid board insulation, and fibreglass batt insulation.

Spray Foam Insulation

Spray foam insulation is a popular and efficient option for metal roofs. It consists of a two-part liquid insulation material that expands and hardens upon application, creating a seamless and airtight insulation layer. Spray foam insulation is known for its excellent thermal resistance, moisture resistance, and sound insulation properties. It can be applied to both new and existing roofs, providing superior coverage and filling gaps and cracks effectively.

However, spray foam insulation requires professional installation due to the specialised application process and equipment involved. It is important to choose between open-cell and closed-cell spray foam based on your specific needs. Open-cell spray foam is more affordable and suitable for larger areas, while closed-cell spray foam offers higher insulation performance and durability.

Rigid Board Insulation

Rigid board insulation, also known as foam board insulation, is a versatile and durable option for metal roofs. It is available in various materials such as polystyrene, polyurethane, and polyisocyanurate. Rigid foam boards have a high R-value, providing excellent thermal resistance and insulation performance. They are resistant to moisture, making them ideal for metal roofing applications. Rigid board insulation is rigid and dense, making it suitable for flat roofs, walls, foundations, and attics.

Proper installation of rigid board insulation is crucial to ensure its effectiveness. The boards should be tightly fitted and installed without any gaps to prevent air infiltration. Additionally, a vapour barrier should be applied to control moisture.

Fibreglass Batts

Fibreglass batt insulation is a cost-effective and widely used option for metal roofs. It consists of fine glass fibres assembled into pre-cut panels or rolls, making it easy to handle and install. Fibreglass batts are available in various R-values, allowing for customization based on insulation needs. They provide good thermal resistance, helping regulate indoor temperatures effectively. Fibreglass batt insulation is environmentally friendly, as it is typically made from recycled glass.

However, proper installation of fibreglass batt insulation is essential to ensure its effectiveness. The batts should be carefully fitted and sealed to prevent air gaps. It is important to note that fibreglass insulation can be hazardous to handle, and appropriate personal protective equipment should be worn during installation. Seeking professional installation is recommended if you are unfamiliar with handling fibreglass insulation.

How to Insulate a Metal Roof

The process of insulating a metal roof may vary depending on whether it is a new roof or an existing roof. Here, we will outline the general steps for each scenario and provide tips for specific insulation materials.

Insulating a New Roof

When insulating a new metal roof, it is best to incorporate insulation during the construction or installation process. This allows for a seamless integration of insulation materials and ensures optimal coverage.

  • Prepare the surface: Before installing the insulation, ensure that the roof surface is clean and free of debris.
  • Install the insulation material: Follow the manufacturer’s instructions for the specific insulation material chosen. Properly secure the insulation to the roof, ensuring a tight and continuous layer.
  • Apply a vapour barrier: Depending on the insulation material used, a vapour barrier may be required to control moisture. Install the vapour barrier according to the manufacturer’s guidelines.
  • Install the metal roofing: Once the insulation and vapour barrier are in place, proceed with the installation of the metal roofing material, following the manufacturer’s instructions.

Insulating an Existing Roof

Insulating an existing metal roof requires additional considerations, as accessibility and compatibility with the roof structure may vary.

  • Assess the roof condition: Inspect the roof for any leaks, gaps, or damage. Address any necessary repairs before proceeding with insulation installation.
  • Choose the appropriate insulation material: Select an insulation material that is suitable for retrofitting an existing roof. Spray foam insulation and fibreglass batts are commonly used for this purpose.
  • Prepare the surface: Clean the roof surface to ensure proper adhesion of the insulation material.
  • Install the insulation material: Follow the manufacturer’s instructions for the specific insulation material chosen. Ensure a tight fit and proper sealing to prevent air infiltration.
  • Apply a vapour barrier (if necessary): Depending on the insulation material used, a vapour barrier may be required to control moisture. Install the vapour barrier according to the manufacturer’s guidelines.
  • Check for gaps and leaks: Inspect the installed insulation for any gaps or leaks. Seal any gaps or cracks to ensure optimal insulation performance.


Metal roof insulation is essential for maximising energy efficiency, maintaining a comfortable indoor environment, and protecting your property from the elements. By considering factors such as roof condition, insulating ability, budget, and experience, you can choose the best insulation material for your metal roof. Spray foam insulation, rigid board insulation, and fibreglass batt insulation are among the most common options, each offering unique advantages and considerations. Whether you are insulating a new roof or retrofitting an existing one, following the proper installation process is crucial for optimal insulation performance. By investing in metal roof insulation, you can enjoy increased energy savings, improved comfort, and enhanced durability for your property.

For all your metal roof insulation needs, Sydney Roofing Co connects you with reputable roofing companies that specialise in metal roof insulation. Contact us today for expert advice and reliable insulation services.