How to Properly Measure Polyiso Insulation in Accordance with ASTM C1289
Accurate measurement of faced rigid cellular polyisocyanurate (polyiso) insulation is essential for verifying product thickness and ensuring compliance with ASTM C1289 – Standard Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Board. ASTM C1289 establishes acceptable tolerances, which allow for thickness variation within ±1⁄8 inch. It’s important to note that measuring the thickness at the outer edge of the board will not provide an accurate or ASTM-compliant result. Below is a clear, step-by-step guide for properly measuring polyiso insulation using ASTM-aligned methods. Hunter Panels’ recommended procedure follows these same principles.
HOW TO MEASURE POLYISO THICKNESS (ASTM C1289 METHOD)
1. Cut the Board Properly
Cut the board down the middle of the 4-foot dimension so you end up with two pieces measuring 2 feet x 8 feet.
• Avoid using a razor knife for measurement cuts.
• A clean, smooth cut is necessary to expose a true cross-section of the foam.
• A caliper is the preferred measuring tool to ensure accuracy.
2. Take Six (6) Thickness Measurements
ASTM C1289 requires multiple measurements to account for natural surface variation. Take readings as follows:
• Start at least 1 to 2 inches in from the edge (never on the outer edge).
• Take measurements approximately every 2 feet along the board.
• Ensure one measurement is taken at the center of the board.
• This results in six total measurements.
3. Calculate the Average Thickness
After collecting all six readings:
• Add all measurements together.
• Divide by six to obtain the average.
• Compare the calculated average to the manufacturer’s stated thickness.
4. Verify ASTM Tolerance Compliance
The final average must fall within ±1⁄8 inch of the labeled product thickness to meet ASTM C1289 requirements.
In summary, measuring polyiso insulation in accordance with ASTM C1289 is straightforward when you use the correct tools, follow consistent sampling procedures, and take measurements in the right locations. By cutting a clean sample, taking six properly spaced measurements, and calculating an accurate average, you can confidently verify that the insulation meets ASTM standards and project specifications.
If you need additional guidance or support, Hunter Panels’ Technical Services is happy to help.
