Open Cell Insulation On Metal Roofs?

Regularly used on warehouses, industrial units, agricultural barns and garages, metal roofs are popular for their durability, low maintenance, and longevity. However, they can be challenging to insulate properly. Open-cell spray foam insulation has become increasingly popular as a solution to insulate metal roofs thanks to its affordability for the end user and speed in which it can be installed. But, can open-cell spray foam be used on metal roofs? Let’s dive into the topic to find out.

What is Open-Cell Spray Foam Insulation?

Open-cell spray foam insulation is made by mixing chemicals that react and expand when sprayed onto a surface. The foam is applied as a liquid and quickly expands to fill the space, creating an insulating barrier. Open-cell spray foam insulation is known for its ability to provide a high level of insulation while remaining lightweight and cost-effective. It is also a good sound attenuator thanks to its low-density structure but in damp environments, it can soak up moisture from condensation or roof leaks.

Benefits of Open-Cell Spray Foam Insulation

Open-cell spray foam insulation has several benefits, including:

  • Excellent Insulation: Open-cell spray foam insulation is an excellent insulator, making it an ideal choice for keeping your home or building warm in the winter and cool in the summer.
  • Soundproofing: Open-cell spray foam insulation can also help to reduce noise pollution by blocking sound waves.
  • Cost-Effective: Open-cell spray foam insulation is less expensive than closed-cell spray foam insulation, making it an ideal choice for those on a tight budget.


Can Open-Cell Spray Foam Be Used on Metal Roofs?

Yes, open-cell spray foam insulation can be used on metal roofs. However, there are a few things that need to be considered when installing open-cell spray foam insulation on a metal roof:

  • Ventilation: It’s crucial to ensure proper ventilation when using open-cell spray foam insulation on a metal roof. Without adequate ventilation, the insulation can trap moisture, which can cause rust and corrosion on the metal roof.
  • Condensation Point: In moisture-rich environments, open-cell spray foam will do little to repel moisture which means any compound vapour drive may saturate the insulation leading to poor performance.
  • Metal Preparation: The metal roof needs to be properly prepared before applying the insulation. This includes cleaning the surface and removing any loose rust or debris. In addition, the roof should be free from moisture to ensure that the open-cell spray foam does not trap it between the substrate.
  • Professional Installation: The installation of open-cell spray foam insulation on a metal roof should be done by a professional who has experience with metal roofs and insulation installation. Open-cell spray foam expands quickly and can be unsightly as a decorative finish.
  • Weather Conditions: Open-cell spray foam insulation should not be installed during cold weather as the cold temperatures can affect the expansion of the foam and affect its ability to adhere to the substrate effectively.
  • Roof Condition: An assessment of the roof condition should be carried out before the installation. Open-cell spray foam will soak up any moisture from roof leaks, therefore, if the roof is old with failing fixtures, it may hold moisture like a sponge and cause long-term structural damage.
  • Insulated Roof Panels: Where insulated roof panels are already in-situ and are in good condition, there is little reason why open-cell spray foam insulation wouldn’t act as a suitable solution to increase the thermal performance of the roof or add better sound attenuation.
  • Hybrid System: A popular choice for open-cell insulation on metal roofs is to spray-apply a thin 15-20mm layer of closed-cell insulation first to strengthen the existing substrate and the fixings. Open-cell can be spray-applied directly to the closed-cell foam as a hybrid insulation system. (See our case study for
  • Appearance & Aesthetics: Assuming the roof is in perfect condition for the open-cell spray foam, it is important for the end user to consider whether the finished appearance of the open-cell spray foam would impact negatively on the look and feel of the building.

What Open-Cell Is Best For Metal Roofs?

Without appearing to be biased, our Sucraseal Open Cell Spray Foam is the best choice for a metal roof, especially if the foam is to be left exposed. Sucraseal is currently the only British Class 1 Fire-Rated open-cell foam available in the UK and this fire-rating is generally the minimum accepted standard for fire regulations and property insurers. Find out more about Sucraseal here:


Open-cell spray foam insulation can be used on metal roofs as long as proper ventilation, metal preparation, professional installation, appearance and condensation are considered. It’s an excellent choice for those looking for cost-effective insulation that provides excellent insulation and soundproofing. We would strongly recommend using closed-cell spray foam as the primary bonding layer to a metal roof as this will provide structural strength and robust adhesion. The end-user should also consider whether the finished appearance of the open-cell foam is suitable for the internal aesthetics of the building.

If you’re considering open-cell spray foam insulation for your metal roof, consult with a professional insulation contractor to ensure that your insulation is installed correctly and meets your needs.