The use of thermal insulation is a primary approach to reducing heating and cooling loads in buildings, which account for 42 % and 24 % of energy consumption in residential and commercial buildings, respectively, and to decrease energy losses from heat transfer systems used in the petroleum, chemical, iron and steel, and food and beverage industry sectors. This project will yield the measurement science needed to accurately predict the insulating ability of these materials by developing measurement data and techniques to allow for accurate assessment of their thermal properties. The focus is on two particular types of insulating materials: building insulation and industrial insulation meant for applications up to 250 °C.
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 methods (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 through 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 achieving the expected energy savings. 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, and their thermal transmission processes are inherently different from conventional materials. 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 is further development of capabilities to test materials at different gas pressures.
What is the research plan?
The current year's research plan covers four related areas: 1) international comparisons with guarded-hot-plate laboratories at other NMIs; 2) development of NIST thermal insulation data sets at extended temperatures and lower pressures; 3) establishment of Measurement Services for the NIST 500 mm guarded-hot-plate apparatus; and 4) renewal of SRM 1453a.
Following successful intercomparisons with the Laboratoire National de Metrologie et d’Essais and the National Physical Laboratory, NIST will participate in a bilateral comparison with a national metrology laboratory to investigate the impact of gas pressure on the thermal performance of porous solids as part of the method validation for the 500 mm guarded-hot-plate apparatus.
This intercomparison 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 Manuals transitioning to the recently revised ISO 17034, “General requirements for the competence of reference material producers.” 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.
In FY19, NIST commenced 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 FY20, 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 researchers initiated the renewal of SRM 1450e fibrous glass board for thermal resistance by acquisition of the candidate lot of material. In FY18, the bulk density of the candidate lot was determined to provide the optimal sample for subsequent thermal conductivity measurements. Thermal conductivity measurements were conducted in FY19 using the NIST 500 mm diameter guarded-hot-plate apparatus in accordance with a test plan developed by the NIST Statistical Engineering Division. In FY20, EL staff, working NIST SED (776), will complete SP260 documenting renewal of 1450e. NIST SRM 1450, which averages sales of 55 units per annum, is an industry standard for the calibration of heat-flow-meter apparatus and other thermal conductivity instruments. In FY20, EL researchers will begin the process of renewing 1453a, Expanded Polystyrene Board, by conducting market research of candidate materials.