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In-field Building Material Thermal Conductivity and R-value Measurement

Grant Number:   OG-17-005

GRANT ACTIVE DATE

02/01/2017 - 01/31/2018

PROGRAM AREA

Grant

AWARD AMOUNT

80,000.00

PRINCIPAL INVESTIGATOR

Dr Xinwei Wang

LOCATION

Ames, IA

STATUS

active

ORGANIZATION

Iowa State University

FOCUS

At present, building material’s thermal conductivity is often measured in lab under conditions that are far from real scenarios. These conditions include temperatures and temperature gradient, stress, cracking, and material degradation. There is no such technique yet available for in-field thermal conductivity measurement of building materials. Consequently, it is difficult to have an accurate assessment of the energy efficiency of in-service building systems. Current R-value measurement of building materials always involves direct sensor access and time-consuming data collection to insure sound accuracy. In this project, we will develop a novel technique to achieve in-field measuring and mapping of the thermal conductivity (k) of building materials and to evaluate their R-value. The k measurement involves Single-point laser heating and spatial Temperature Differential (STD) measurement by an infrared camera. Our preliminary study has shown that the STD technique is able to measure different aggregate particles and mortar in a high strength concrete sample. Our overarching goal is to develop this technique into a portable device which is capable of measuring the thermal conductivity of various building materials, and evaluating their R-value based on in-situ thickness measurement using ultrasonic thickness gauge with a measurement accuracy of ±0.1 mm. The targeted application environment temperature is -20 ºC to 45 ºC with a humidity level of 0~100%. With development in the test device and data analysis tools of this new technology (to be funded by Iowa Energy Center under this project), we will pursue external funding from National Institute of Standards and Technology and industries toward novel methods and strategies for building energy efficiency assessment and improvement.