‍Metal roofing has become increasingly popular due to its durability and long lifespan. However, to maximise its energy efficiency and create a comfortable living environment, proper insulation is crucial. In this comprehensive guide, we will explore the importance of installing insulation under metal roofing and provide a step-by-step process for installation. Whether you’re considering a new roof or looking to add insulation to an existing one, this article will help you understand the options available and make an informed decision.

Why Insulate Under Metal Roofing?

Insulating your metal roof offers several benefits, including improved energy conservation, noise reduction, and protection against the elements. Metal roofs, without insulation, can allow the transfer of hot or cold air, resulting in higher energy bills and discomfort. By adding insulation, you can create a thermal barrier that keeps your home warm in the winter and cool in the summer, leading to energy savings and enhanced comfort.

Insulation also plays a crucial role in reducing noise pollution. Metal roofs can be noisy during heavy rain or strong winds. Installing insulation helps dampen these sounds, creating a quieter living environment. Additionally, insulation helps prevent condensation buildup, which can lead to structural damage over time. By controlling moisture levels, insulation helps maintain the integrity of your metal roof and prolong its lifespan.

Factors to Consider Before Installing Insulation

Before diving into the insulation installation process, there are several factors to consider to ensure you choose the right type of insulation for your specific needs.

Roof Condition

The condition of your roof will influence the insulation method and materials you should use. If you’re working on an existing roof, it’s essential to address any gaps or leaks before installing insulation. Insulation will be less effective if air can escape through these openings. Conduct a thorough inspection and make any necessary repairs before proceeding with insulation installation.

Insulating Ability

Different insulation materials have varying levels of thermal resistance, measured as the R-value. The higher the R-value, the better the insulation’s ability to resist heat flow. Consider your location and climate when selecting insulation materials. Consult with insulation suppliers or professionals to determine the minimum R-value suitable for your home.


Your budget will also play a significant role in determining the type of insulation you choose. Some insulation options are more expensive than others. Assess your budget and weigh the costs against the expected benefits and long-term energy savings. Remember that investing in higher-quality insulation may provide better performance and durability in the long run.

Experience and Equipment

Insulation installation can be a complex process, depending on the material and method chosen. Consider your level of experience and the tools required for installation. Certain insulation types, such as spray foam, may require specialised equipment and professional expertise. If you’re unfamiliar with the installation process or lack the necessary tools, it’s advisable to hire professionals to ensure proper installation and optimal performance.

Understanding Your Insulation Options

Now that you’ve considered the key factors, let’s explore the different insulation options available for metal roofing. Each option has its advantages and considerations, so it’s essential to choose the one that best suits your needs and budget.

Fibreglass Batts

Fibreglass batt insulation is a popular and cost-effective option for insulating metal roofs. It consists of fine glass fibres woven together to create a thick insulating layer.


  • Affordability: Fibreglass batts are one of the most budget-friendly insulation options.
  • Versatility: They can be cut and shaped to fit your specific roof structure and requirements.
  • Ease of installation: Fibreglass batts are relatively easy to install, making them suitable for DIY projects.
  • Environmental friendliness: Many fibreglass batts are made from recycled glass, making them an environmentally-conscious choice.


  • Safety concerns: Handling fibreglass batts can be hazardous if proper protective gear is not worn.
  • Limited moisture resistance: Fibreglass insulation may not be the ideal choice for areas prone to moisture buildup.

Price Range: The cost of fibreglass batt insulation varies depending on the desired R-value. On average, it ranges from $0.12 to $0.16 per square foot for an R-value of 11 and $0.55 to $0.60 per square foot for an R-value of 38.

Rigid Board Insulation

Title: Expert Guide: Installing Insulation Under Metal Roofing | Sunshine Coast Roofers
Meta-description: how to install insulation under metal roofing

Description: rigid board insulation

Rigid board insulation, also known as foam board insulation, offers excellent thermal resistance and durability. It comes in sheets or panels made from materials such as polystyrene, polyurethane, or polyiso.


  • High thermal resistance: Rigid board insulation provides superior thermal insulation, reducing heat transfer effectively.
  • Air and water resistance: Its density and thickness help minimise air leakage and prevent water infiltration.
  • Ease of installation: When properly fitted and sealed, rigid foam boards offer a relatively straightforward installation process.


  • Tight fitting requirements: Rigid board insulation must be precisely fitted to prevent gaps that can compromise its effectiveness.
  • Sealing requirements: Joints and seams must be adequately sealed to prevent air leakage and ensure optimal performance.
  • Vulnerability to UV damage: Rigid foam insulation is susceptible to damage from prolonged exposure to UV rays, requiring proper installation and protective measures.

Price Range: The cost of rigid board insulation typically ranges from $3.95 to $7.20 per square foot, depending on the quality and thickness.

Spray Foam Insulation

Title: Expert Guide: Installing Insulation Under Metal Roofing | Sunshine Coast Roofers
Meta-description: how to install insulation under metal roofing

Description: spray foam insulation

Spray foam insulation is a highly effective option for insulating metal roofs. It involves the application of a two-part liquid insulation material that expands and hardens upon contact with air.


  • Excellent thermal insulation: Spray foam insulation provides superior thermal resistance and minimises heat transfer.
  • Versatile application: It can be applied to both new and existing roofs without the need for extensive modifications.
  • Air sealing: Spray foam insulation creates an airtight seal, minimising air leakage and enhancing energy efficiency.
  • Moisture and pest resistance: Its application helps prevent condensation buildup and reduces the risk of insect or rodent infestations.


  • Professional installation recommended: Spray foam insulation requires specialized equipment and expertise for proper application, making professional installation advisable.
  • Higher cost: Compared to other insulation options, spray foam insulation can be more expensive due to the required equipment and professional labor.

Price Range: Spray foam insulation is available in two types: closed-cell and open-cell. Closed-cell spray foam generally costs $1 to $1.50 per board foot, while open-cell spray foam ranges from $0.44 to $0.65 per board foot.

How to Install Insulation Under Metal Roofing

Title: Expert Guide: Installing Insulation Under Metal Roofing | Sunshine Coast Roofers
Meta-description: how to install insulation under metal roofing

Description: person installing insulation under metal roofing

The installation process for insulating metal roofing depends on whether you’re working with a new roof or an existing one. Here, we’ll outline the steps for both scenarios.

Installing Insulation on a New Roof

  • Prepare the surface: Ensure that the roof surface is clean and free from debris. Wash or clean the area to remove any dirt or loose particles.
  • Install plywood: Lay plywood sheets perpendicular to the roof joists to act as structural roof sheathing. Use roofing nails to secure the plywood in place.
  • Apply house wrap: Place a layer of house wrap or building paper over the plywood sheathing, overlapping each sheet by six inches. Use nails or staples to fasten the house wrap, creating a moisture and leak-resistant barrier.
  • Install rigid foam insulation: Place rigid foam insulation sheets over the entire surface of the roof. Ensure a tight fit between the sheets, avoiding overlapping. Use adhesive or fasteners to secure the insulation in place.
  • Seal the seams: Apply duct tape or another appropriate sealant to seal the seams between the insulation sheets. This step helps prevent air and moisture infiltration.
  • Install the metal roofing panels: Follow the manufacturer’s instructions to install the metal roofing panels over the insulation. Ensure proper alignment and secure the panels according to the recommended fastening method.

Adding Insulation to an Existing Roof

  • Assess the roof structure: From inside the attic, examine the underside of the metal roof. Identify any gaps or areas between the roof sheathing and framing system.
  • Install fibreglass batts: Place fibreglass batts into the gaps between the roof sheathing and framing system. Ensure a loose fit to avoid reducing the insulation’s effectiveness. Be cautious and wear appropriate protective gear while handling fibreglass batts.
  • Cover wider spans with rigid foam insulation: For larger areas between joists, use rigid foam insulation sheets. Cut the sheets to the appropriate size and secure them in place with staples or adhesive.
  • Seal joints and gaps: Apply sealant or tape to seal any joints or gaps between the rigid foam insulation sheets. This step helps prevent air leakage and enhances the insulation’s performance.


Insulating your metal roof is essential for maximising energy efficiency, reducing noise pollution, and protecting your home from the elements. By considering factors such as roof condition, insulating ability, budget, and your own expertise, you can choose the most suitable insulation option. 

Whether you opt for fibreglass batts, rigid board insulation, or spray foam, following the correct installation process is crucial for optimal performance. By insulating your metal roof, you’ll create a more comfortable living environment and enjoy long-term energy savings. 

Don’t hesitate to consult with professionals to ensure you choose the best insulation solution for your specific needs.