Objective - To achieve reductions in building heating and cooling loads and industrial energy use by decreasing measurement uncertainties of the thermal resistance of insulating materials through the assessment of room- and high-temperature insulating materials measurement capabilities (i.e., laboratory comparisons) and investigation of measurement techniques for novel insulating materials.
What is the new technical idea? One of the most cost effective ways of reducing building energy consumption and associated greenhouse gas emissions is thermal insulation. Insulation in the building envelope, thermal appliances, and process industries greatly reduces the demand for space conditioning, hot water, and other thermally active processes. Accurate determination of the insulating capability of these materials is critical to achieve the expected energy savings. In order to facilitate international trade beneficial to U.S. industry, a vital aspect in the development of a measurement program for thermal insulation is the verification of standardized test methods with other national metrology institutes (NMIs) at different temperatures and pressures. Equally important is the subsequent development of reliable thermal conductivity data sets at different temperatures and pressures for the public. NIST will address this problem by 1) participating in international laboratory comparisons with other NMIs; and 2) developing data sets that provide accurate thermal transmission values at elevated temperatures for use by testing laboratories in calibrating test equipment. After developing confidence in measurements and promulgating test data, NIST will develop measurement services and reference materials for use by industry in calibrating equipment used to determine thermal performance of insulation. Another key challenge is determining the insulating capabilities of innovative insulating materials. Novel insulating materials have been proposed to reduce heating and cooling loads in buildings, but the measurement science challenges have not been fully solved. Some materials with potential for greatly reducing energy consumption in buildings include phase change materials, vacuum insulation panels, and micro-porous materials such as aerogels. In FY17, NIST assessed test methods for phase change materials. In subsequent years, NIST is preparing instruments that can be used to assess other building materials. One example of such preparations are further development of capabilities to test materials at varying ambient pressures.
What is the research plan? The current year's research plan covers five related areas: 1) international comparisons with guarded-hot-plate laboratories at other NMIs; 2) development of NIST thermal insulation data sets at extended temperatures; 3) establishment of Measurement Services for the NIST 1016 mm guarded-hot-plate apparatus and the NIST 500 mm guarded-hot-plate apparatus; 4) development of NIST test data on phase change materials; and 5) renewal of SRM 1450e.
Following successful intercomparisons with the Laboratoire National de Metrologie et d’Essais and the National Physical Laboratory, NIST will participate in the following comparisons as part of the method validation for the 500 mm guarded-hot-plate apparatus:
- Bilateral comparison with National Research Council Canada to investigate the impact of pressure on the thermal performance of porous solids.
- Multi-lab comparison conducted by the Asia Pacific Metrology Program (APMP.T-S10) under the International Bureau of Weights and Measures (BIPM).
- Collaboration in a multi-year European Metrology Research Program for evaluation of the guarded-hot-plate method under high temperatures.
These intercomparisons will help determine best practices in measuring insulation at conditions departing from typical ambient conditions to ensure accurate measurement results. In conjunction with the laboratory comparisons and the uncertainty analysis previously conducted, researchers will prepare the laboratory Quality Manual for the 500 mm guarded-hot-plate measurement services. Data from these intercomparisons will begin to populate the datasets intended for release as part of Standard Reference Database 81 (NIST Heat Transmission Properties of Insulating and Building Materials: http://srdata.nist.gov/insulation/) in future years.
NIST researchers will initiate the renewal of SRM 1450e fibrous glass board for thermal resistance. The bulk density of the candidate lot purchased in FY17 will be determined to provide the optimal sample for subsequent thermal conductivity measurements. Thermal conductivity measurements will be conducted using the NIST 500 mm diameter guarded-hot-plate apparatus in accordance with a test plan developed by the NIST Statistical Engineering Division. NIST SRM 1450, which averages sales of 50 units per annum, is an industry standard for the calibration of heat-flow-meter apparatus and other thermal conductivity instruments.
In FY18, NIST will commence measurement services for thermal resistance of building insulation using the NIST 1016 mm diameter guarded-hot-plate apparatus. To satisfy anticipated demand, NIST will coordinate the test schedule with industry providing measurement services throughout FY18, as needed. After validation, the 1016 mm guarded-hot-plate apparatus will also be used to maintain internal calibrations of the heat-flow-meter apparatus and to continue investigations of advanced insulations, such as microporous insulation and vacuum insulation panels in future years. Those investigations will assist in developing best practices for these novel insulation materials.
NIST will begin to develop data on phase change materials and evaluate the accuracy of recent test standards for these materials. Data on thermal transmission properties as well as thermal capacitance will be gathered, with the intention that the data be made available to the public at a later date.