ASTM C1338 Standard Test Method for Determining Fungal Resistance of Insulating Materials and Coatings

The standard “ASTM C1338 Standard Test Method for Determining Fungal Resistance of Insulating Materials and Coatings” developed by the American Society for Testing and Materials (ASTM) describes a test method for determining the ability of new insulation materials and their coatings to resist fungal growth.

The type of material used in the manufacture of insulation products and the type of membrane used to cover these products can sometimes affect fungal growth under high humidity conditions. This test method is used to determine the relative resistance of insulation and its coating to fungal growth under conditions favorable for fungal growth.

This test method uses a comparative material to determine a material's relative resistance to fungal growth. In some specific product areas, the absence of fungal growth is required. In such cases, the use of the comparative material is omitted, and the pass/fail criterion is determined by fungal growth.

During this test, test samples are inoculated with fungal spores and incubated for 28 days. After incubation, samples are visually inspected for fungal growth. Comparative materials are also tested for performance analysis.

This standard ensures that insulation materials are resistant to fungal growth in humid conditions. Their long-term performance is verified by testing under controlled environmental conditions.

Testing typically takes 4-6 weeks. Results are evaluated by visually inspecting samples for fungal growth after 28 days of incubation. No visible fungal growth should be observed in test samples after 28 days of incubation.

The ASTM C1338 standard test method is used to determine the fungal resistance of insulation materials and coatings. Ensuring that insulation materials resist fungal growth is crucial as it helps maintain indoor air quality. This prevents the material from deteriorating and becoming susceptible to mold growth, which can potentially pose health risks.

This standard applies to insulation materials and coatings that claim fungus resistance. This includes materials used in unfinished floors, ceilings, walls, and other new construction areas where high humidity and high temperatures can support fungus and mold growth.

The main testing requirements are:

• Environmental chamber: An experimental setup that maintains a temperature range of 28-30 degrees Celsius and a relative humidity of 95 percent to support fungal growth.
• Test microorganism: Aspergillus niger spore suspension is used as the test microorganism.
• Test samples: Three samples of the insulation material are prepared and used.
• Control samples: Customers can send comparative material to analyze the performance of test samples against fungal growth.

Fungi grow rapidly in insulation and coatings in moist and humid environments. ASTM C1338 helps evaluate the relative ability of these products to support or resist mold/fungal growth under controlled laboratory conditions. These controlled conditions are closely simulated to mimic the favorable conditions, such as high humidity, required for fungal growth.

Another important feature of this test method is that it uses a comparative material to determine the resistivity or susceptibility of the test material. However, some specified products must be completely resistant to fungal growth. In such cases, a comparative material is not required, and the product's effectiveness is determined by whether fungal growth occurs.

As a result, ASTM C1338 provides a standardized approach for evaluating insulation materials, providing insights into their resistance and effectiveness against fungal growth. Advanced laboratories utilize advanced testing and analytical technologies to implement antifungal efficacy protocols.

Essentially, the ASTM C1338 standard covers:

• Testing of insulation materials: This standard applies to new insulation materials and coatings used in unfinished floors, ceilings, walls and other construction areas where high humidity and high temperatures promote fungal growth.
• Qualitative assessment: Determines the relative resistance of materials to fungal growth under controlled conditions conducive to fungal growth.
• Comparative testing: This method typically uses a comparative material to measure the fungal resistance of the test sample. In special cases, a pass/fail criterion is applied where fungal growth is not permitted.

The ASTM C1338 standard is considered important for the following reasons:

• Fungal growth such as mold and mildew can have serious consequences in buildings. For example,
  • Indoor air quality: Mold can release spores that impair air quality, causing respiratory problems and allergies.
  • Material degradation: Fungal growth can weaken insulation materials, reducing their thermal performance and structural integrity.
  • Health risks: Long-term exposure to mold can lead to health problems, making fungal resistance a critical feature for insulation in moisture-prone environments.
• This standard ensures insulation materials can withstand these challenges, providing manufacturers with a reliable method to certify their products' fungal resistance. This certification enhances product reliability and supports claims of durability and safety in high-humidity environments.

The ASTM C1338 standard test method includes a controlled test setup to simulate conditions favorable for fungal growth. A general summary of the procedure is as follows:

• Test microorganism: Spore suspension of Aspergillus niger, a common mold species, was used as the test microorganism due to its widespread occurrence and ability to grow in moist conditions.
• Environmental chamber: The test is conducted in an environmental chamber maintained at 28-30 degrees Celsius and 95 percent relative humidity to create optimum conditions for fungal growth.
• Sample preparation: To ensure reliable results, three samples of the insulation material or coating are prepared.
• Inoculation: Samples are inoculated with a mixed culture of fungal spores using an atomizer to ensure even distribution.
• Incubation: Inoculated samples are incubated for 28 days, allowing sufficient time for fungal growth to occur if the material is susceptible.
• Evaluation: After incubation, samples are visually inspected for fungal growth. The amount of growth is compared to a control material or, in some cases, a pass/fail criterion is applied where growth is not permitted.

Unlike some antifungal tests, ASTM C1338 allows for some degree of fungal growth, focusing on the material's relative resistance compared to a control. This is particularly suitable for insulation materials that do not need to be completely impervious to fungi but must offer sufficient resistance for practical use.

The ASTM C1338 standard applies primarily to insulation materials and coatings used in:

• Residential construction: Insulating the walls, ceilings and floors of homes, especially in humid climates or areas such as basements.
• Commercial buildings: Insulation in heating, ventilation and air conditioning (HVAC) systems where moisture accumulation is common.
• Industrial environments: Insulation in high humidity facilities such as warehouses or manufacturing facilities.

Products that pass ASTM C1338 testing can be labeled as tested to that standard, providing manufacturers with third-party validation to support fungal resistance claims. This is particularly important for ensuring compliance with marketing and building codes and regulations.

Our organization, which has been operating for many years and meticulously follows global developments in science and technology, employs a team of experienced professionals and a broad infrastructure to conduct testing, measurement, and analysis in a wide range of areas for businesses across all sectors. In this context, we also provide testing services in accordance with the "ASTM C1338 Standard Test Method for Determining the Fungal Resistance of Insulation Materials and Coatings."