Thermal Transmission Testing and ASTM C518: Ensuring Reliable Insulation Performance

Accredited thermal transmission testing for insulation and building materials

Thermal transmission testing evaluates how heat moves through a material, information that is essential for designing energy efficient buildings, verifying insulation performance, and meeting code or product label requirements.

QAI provides accredited thermal transmission property testing using recognized methods to measure thermal conductivity, thermal resistance (R-Value), and thermal resistivity (R-Value per inch or RSI) for a wide range of insulation and building materials. Our specialists guide you from sample preparation through ASTM C518 compliant testing and certification, so results are easy to understand and ready for submission to regulators, customers, and specifiers.

Whether you are validating a new insulation product, comparing materials, or documenting building envelope performance, QAI delivers precise data, clear reports, and responsive support to help you make confident, compliance ready decisions.

ASTM C518 Thermal Transmission Testing

Understanding how heat moves through a material is essential for evaluating insulation performance, energy efficiency, and code compliance across a wide range of building and construction products. QAI’s thermal transmission property testing measures thermal conductivity, thermal resistance (R value), and thermal resistivity (RSI) to help manufacturers validate product claims, meet regulatory requirements, and improve material performance.

Using the ASTM C518 Heat Flow Meter Method, our laboratories measure how effectively insulation and building materials resist heat transfer. The resulting data supports engineering decisions, certification programs, and product acceptance in building codes and specifications.

Thermal Transmission Properties In Practice

When people talk about thermal transmission, they’re asking: “How easily does heat pass through this material?” We answer that question by measuring three related properties:

• Thermal conductivity: how readily heat flows through the material itself. Lower values usually mean better insulation performance.
• Thermal resistance (R‑value): how strongly the material resists heat transfer across its full thickness. Higher R values indicate better insulation performance.
• Thermal resistivity (RSI or R value per inch): the thermal resistance per unit thickness of material. This value is commonly used to compare insulation materials and is often required where performance per inch is specified.

These fundamentals help manufacturers and builders evaluate building thermal performance, reduce energy loss, and choose the right insulation thickness for walls, roofs, and assemblies.

From Testing to Certification

QAI clients benefit from a streamlined compliance pathway serving both the Canadian and American markets, supported by customer‑focused project management teams that guide you through each step of the testing and certification process.

As a one‑stop solution for testing, inspection, and certification (TIC), QAI eliminates the need to coordinate multiple laboratories or agencies. With multiple locations across North America and more than 30 years of expertise in the TIC industry, we help clients accelerate timelines, reduce administrative burden, and achieve consistent, high‑quality results.

QAI’s Service Scope

Our thermal testing services include the following:

1. Project Scoping & Sample Guidance
   We help clients determine testing goals, whether you require R‑value testing, thermal conductivity of insulation, comparative performance analysis, or formal certification. Our team offers clear instructions for sample size, thickness, conditioning, facers, and preparation.
2. Laboratory Testing
   In QAI’s accredited thermal test laboratories, we measure insulation and building materials under controlled conditions to determine thermal conductivity, thermal resistance (R value), and thermal resistivity (R value per inch). These results support insulation material evaluation, thermal insulation certification, and compliance with applicable building code insulation requirements.

1. Standards, Methods & Data Quality
   We align each project with the appropriate testing requirements across ASTM, CAN/ULC, NFRC, NAFS/CSA, NFPA, TAS , an other applicable standards. This ensures your results are fully recognized for certification, code compliance, and market acceptance.
2. Clear Reporting & Decision Ready Outputs
   QAI delivers user friendly reporting that explains thermal property measurements, environmental conditions, and resulting performance values. Reports are designed to support code submittals, product labeling, and engineering decisions.
3. Typical Products and Equipment We Test

ASTM C518 heat flow meter testing

R-Value and RSI reporting for insulation comparisons

General Building Products

Decision-ready reports for submittals and compliance files

1. Long Term Thermal Resistance (LTTR) Testing – CAN/ULC S770
   For insulation products where long term performance is critical, QAI offers Long Term Thermal Resistance (LTTR) testing in accordance with CAN/ULC S770. This method evaluates how the thermal resistance of certain foam plastic insulation materials changes over time through an accelerated aging procedure.

   LTTR testing is commonly required for closed cell insulation products such as polyisocyanurate and extruded polystyrene, where thermal performance can decline as blowing agents diffuse. The test provides a stabilized thermal resistance value that better represents in service performance over the life of the product.

   By combining ASTM C518 testing with CAN/ULC S770 evaluation, QAI helps manufacturers demonstrate both initial and long term thermal insulation performance for code compliance, product certification, and building science applications.

What You Get With QAI

QAI strengthens your thermal testing and compliance process through industry‑recognized expertise and comprehensive support:

• Streamlined compliance projects for both Canadian and American markets
• Customer‑focused project management for fast, clear communication
• A one‑stop solution for testing, inspection, and certification (TIC)
• Multiple lab locations across North America, reducing turnaround time
• More than 30 years of TIC experience, ensuring accuracy and consistency
• Availability of Code Compliance Reports to support regulatory and buyer requirements

These advantages help you bring fully tested, certified, and compliant products to market with confidence.