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Assessment of High-Temperature and Innovative Insulation Thermal Performance Project

Summary:

The use of thermal insulation is a primary approach to reducing heating and cooling loads in buildings, which account for 42%1 and 24%1 of energy consumption in residential and commercial buildings, respectively and to decrease energy losses from heat transfer systems that overlap 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 the thermal properties of insulating materials. The focus is on three particular types of insulating materials with high degrees of uncertainty in the measured thermal performance: insulation meant for applications up to 250 °C, microporous insulation, and phase-change materials.

 


[1] 2010 Buildings Energy Data Book, Table 2.1.6 and 3.1.5, respectively.

 

Description:

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 by 2015 through the assessment of 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 and thermal appliances for refrigerators, and air-conditioning units, and process industries such as furnaces, boilers, piping, 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) development of data sets that provide accurate thermal transmission values at elevated temperatures for use by testing laboratories in calibrating test equipment. 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. NIST will initiate an effort to assess the possibilities for such materials to reduce energy consumption in buildings and to address the gaps in the measurement science needed to effectively implement these materials.

What is the research plan? The research plan for FY 14 covers three 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 3) development of measurement science techniques for innovative thermal insulation materials. The process for conducting an inter-laboratory study is a multiyear effort culminating in comparison results for quality assurance. The comparison effort consists of the following general steps.

  • Careful planning including the basic design, test method, laboratory participants, materials, observations per material, and written protocol.
  • Conducting the testing phase of the study: either a bilateral pilot run or a full-scale run.
  • Analysis of the test data utilizing tabular, graphical and statistical diagnostics.

For FY14, NIST will conduct a bilateral comparison of guarded-hot-plate laboratories with the Laboratoire national de metrologie et d’essais (LNE FR). Two thermal insulation standards will be circulated between the laboratories and tests will be conducted at or near ambient temperatures in the recently commissioned 0.5 m guarded-hot-plate apparatus. NIST will continue a bilateral comparison of high -temperature guarded-hot-plate apparatus with the National Physical Laboratory (NPL UK) which has been delayed while specimens suitable for temperatures to 250 °C could be obtained. NIST will also participate as an invited collaborator in a multi-year European effort of mutual interest entitled Metrology for Thermal Protection Materials which includes evaluation of the guarded-hot-plate method for high temperatures.

In FY13, a contractor to NIST investigated the dependency of thermal conductivity on gas pressure which, in conjunction with the pore size of the insulation, essentially limits gas conduction among the interstices (pores) of the insulation material. The effective thermal conductivity curve of porous materials typically decreases about 80 %, or more, as the gas pressure is decreased. In FY 14, predictive models, developed initially for NIST measurements of fibrous insulation, will be extended to powders and eventually to innovative insulation such as vacuum insulated panels. We will also begin tests of phase change material(s) using the heat-flow-meter apparatus in a transient mode of operation. In order to calibrate the heat-flow-meter apparatus, the NIST 1016 mm guarded-hot-plate apparatus will require refurbishment for continued operation. These studies will continue to assist in the identification of key measurement science challenges that must be overcome before such materials can assist in reducing thermal loads in buildings.

Major Accomplishments:

Outcomes:

  • Re-issue SRM 1453, Expanded Polystyrene Board, for thermal conductivity by NIST Office of Reference Materials (640).
  • Zarr, R. R. and A. L. Pintar, "Standard Reference Materials: SRM 1453, Expanded Polystyrene Board, for Thermal Conductivity from 281 K to 313 K," NIST Special Publication 260-175.

Impact of Standards and Tools:

  • NIST-issued Standard Reference Materials for Thermal Insulation mandated by law to be used by insulation industry to meet Federal Trade Commission labeling rules.