Developing Accurate Test Equipment and Methods for Measuring the Thermal Performance of Small Samples of Insulation Having Low Thermal Conductivity

The development of insulation materials having very high thermal resistances (R>14/inch) is of keen interest to BTO. Numerous research projects have been funded in this space ranging from coatings to improve the thermal performance of single pane glazing systems to the development of insulation materials for building envelopes. All these projects have struggled in the development of new material technologies due to the difficulty associated with the measurement of thermal conductivity of small, high thermal resistance materials. As new materials are being developed, the size of each test specimen impacts the cost of development.

When developing new materials, these requirements appreciably increase the cost and time required to prepare test materials and obtain accurate thermal measurements. ORNL will develop standardized test methods to enable the rapid thermal evaluation of advanced insulation materials. Fast, accurate, and reliable thermal metrology to assess thermal properties of new insulation materials, such as novel very low thermal conductivity nanomaterials, in small material sample sections, easy sample preparation, and minimal data analysis requirements, is the desired outcome of this project. ORNL will form a consortium of national laboratories to ensure any new measurement technique meets the needs of the lab researchers, as well as other research organizations, such as universities and NIST, with relevant subject matter expertise. ORNL will engage relevant ASTM technical committees or advisory groups, as well as metrology apparatus manufacturers at an opportune time.

Project Impact

The accurate thermal characterization of low thermal conductivity materials is needed so that researchers developing these technologies can have an accurate assessment of the impact of material modifications. An output of this project will be the relationship between thermal conductivity, sample size, thickness, an instrument sensitivity on the accuracy of the measurement. This will allow the researcher to estimate the uncertainty of their experiment for any combination of these parameters. Undertaking these measurements confidently on small sections of material speeds up the development process as smaller quantities of new formulations need to be produced. This feature also reduces cost.

If these procedures are accepted by the insulation community and code bodies, data on these new insulation products can then be used to satisfy performance reporting requirements. Furthermore, the cost of the new testing equipment needs to be reasonable. Given that the market for the test equipment is small, the selection of a commercially available apparatus that might require refinement or tweaking will most likely cost much less than a test method not based on an existing test device. The team will work with test equipment manufacturers to introduce the proposed changes to test equipment design and seek their guidance regarding the difficulties of combining these new features into existing test equipment.

To gain code body approval, the test method must be written as a consensus standard. As the development of the new test procedures unfold, the team will be working with the appropriate committees within ASTM to modify and/or create a standard around the research work being performed. Staff is already in place to accomplish this activity.