Can Pir Insulation Be Left Outside?

Proper external insulation plays a role in reducing energy consumption and lowering utility bills. However, one common question is whether PIR insulation can be left outside or if it requires protection from the elements. In this article, we will answer and discuss this question in detail. Read on to learn the information you need to make an informed decision.

What is PIR Insulation?

PIR insulation is a closed-cell rigid foam insulation material composed of a thermoset plastic derived from isocyanurate. It is commonly used in roofing, walls, and flooring systems, as well as in the construction of cold storage facilities and refrigerated trucks.

Durability and Weathering Resistance of PIR Insulation

One of the key advantages of PIR insulation is its moisture resistance and weathering capabilities. The structure of PIR insulation makes it highly resistant to water absorption which reduces the risk of moisture-related degradation. Additionally, PIR insulation is designed to withstand exposure to UV radiation, rain, and snow to a certain extent and for many is the best type of insulation for this task.

However, extended and direct exposure to the weather may affect its function and lifespan. Also, you need to note that PIR insulation is not a load-bearing material. It can provide some resistance to compressive forces but it is not designed to support significant loads or structural elements. 

PIR insulation is lightweight and relatively brittle, making it unsuitable for bearing the weight of heavy loads. In construction applications, PIR insulation is typically used as an insulating layer between structural components and should not be relied upon for load-bearing purposes.

Factors Affecting the Outdoor Performance of PIR Insulation

Several factors can influence the outdoor performance of PIR insulation, including:

  1. Temperature fluctuations: Extreme temperature variations can cause expansion and contraction which will potentially lead to cracking or deformation of the insulation material.
  1. Wind: Strong winds can damage or dislodge improperly installed or unprotected PIR insulation.
  1. Humidity: High humidity levels can increase the risk of moisture infiltration and potential degradation over time.

Can PIR Insulation Be Left Outside Permanently?

It is not suggested to leave PIR insulation outside permanently. Although it possesses some resistance to weathering, most manufacturers and industry guidelines do not recommend leaving it permanently exposed to the elements. Prolonged and direct exposure to sunlight, rain, wind, and temperature extremes can degrade the material over time, reducing its insulation performance and potentially causing structural issues.

Short-term vs. Long-term Exposure

  1. Short-term exposure: Typically refers to a period of a few weeks to a couple of months during the construction or installation process. This period allows for the temporary exposure of PIR insulation to the elements while the protective coverings or finishes are being installed.
  1. Long-term exposure: Generally refers to any exposure beyond several months or years. This extended period of direct exposure to the elements can lead to deterioration of the PIR insulation’s performance and structural integrity.

Proper Installation and Protection for Outdoor PIR Insulation

  1. Carefully review and follow the manufacturer’s installation instructions and recommendations for outdoor applications.
  1. Applying weatherproofing membranes, cladding, or other protective coverings over the PIR insulation can shield it from direct exposure to the elements.
  1. Properly seal all joints, seams, and edges to prevent moisture infiltration and air leakage.
  1. Periodically check for signs of damage, moisture penetration, or degradation, and address any issues promptly to prevent further deterioration.


So, can you leave PIR insulation outside with no protection? The answer is no. It can be left outside temporarily but the problem is, you may forget about it if you don’t put protection immediately as soon as you start installing it.

It may cost you more if you neglected to protect in the beginning. Don’t hesitate to invest in quality insulation materials and installation practices. The initial investment may be higher, but the long-term benefits in terms of energy savings, comfort, and peace of mind will undoubtedly pay off in the long run.

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