In-Situ R-Value Measurement Using Multi-Temperature Steady States
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Solution Overview
Problem
Existing methods for determining R-values of materials, particularly roof assemblies, are destructive, costly, compromise waterproofing, and suffer from significant uncertainty due to boundary conditions and temperature fluctuations, with conventional heat flux transducers introducing inaccuracies up to 15%.
Innovation Solution
A non-destructive, in-situ method and system for determining R-values by maintaining multiple steady-state temperatures, using heat flux transducers and temperature sensors to calculate R-values at each temperature, and employing a computing device for data analysis to determine the R-value at a mean temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional heat flux transducer approaches are used to measure R-values, then thermal performance can be estimated, but measurement precision deteriorates with uncertainty of at least 15% due to boundary conditions and temperature fluctuations
Solution Approach 1:
The patent introduces a controlled test assembly with known thermal properties as an intermediary reference standard. By comparing the heat flux measurements through the unknown material against this known reference, the system eliminates the need to directly account for complex boundary conditions and temperature fluctuations, thereby improving measurement precision and reliability
Solution Approach 2:
The system varies temperature parameters across multiple steady-state conditions and measures R-values at different temperatures. By analyzing how R-values change with temperature and extrapolating to a reference temperature, the method compensates for temperature-dependent thermal performance and reduces measurement uncertainty
2Measurement precision
If destructive test approaches are used to determine R-values, then laboratory measurements can be obtained, but the roof assembly is damaged and replacement costs are incurred
Solution Approach 1:
The test assembly is designed to be self-contained and self-supporting, with the unknown material sample serving as part of the structural load path. The assembly can be installed and removed without requiring damage to the underlying roof structure, allowing in-situ testing while preserving the roof's integrity
Solution Approach 2:
A removable test assembly acts as an intermediary device that provides laboratory-grade measurement capabilities without requiring destructive sampling. The test assembly includes all necessary instrumentation and structural elements to perform accurate R-value measurements while being fully reversible and non-invasive to the roof
3Object-generated harmful factors
If endoscopy approaches are used to estimate thermal performance, then replacement costs are avoided, but uncertainty increases due to lack of drawings and material specifications
Solution Approach 1:
The patent replaces visual inspection and documentation-based estimation methods with actual physical heat flux measurements. By directly measuring heat transfer through the installed material using calibrated sensors and controlled test assemblies, the system obtains quantitative data that eliminates uncertainties associated with missing drawings or speculative material properties
Solution Approach 2:
The test assembly is designed to work with the existing roof structure as-is, requiring no modifications or additional information about the original construction. The system self-calibrates using the known reference standard and directly measures the actual in-situ thermal performance, making it independent of documentation quality
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Provides accurate, cost-effective, and time-efficient R-value measurements on existing buildings or construction materials, reducing uncertainty from boundary conditions and temperature fluctuations, and ensuring compliance with energy codes.
Implementation Method 1
a temperature control system for heating and cooling inside the chamber to adjust between three or more steady-state temperatures in the chamber
Implementation Method 2
a temperature control system for heating and cooling inside the chamber to adjust between three or more steady-state temperatures in the chamber
Implementation Method 3
one or more heat flux transducers for measuring heat transfer across the material within the chamber
Implementation Method 4
one or more temperature sensors for measuring a temperature within the chamber
Data Source
AI summary
A method for non-destructive in-situ determination of the R-value of a material at a mean temperature comprises maintaining three or more steady-state temperatures, each for a respective measurement period, measuring temperature and heat flow through the material, calculating R-values at each steady-state temperature and determining the R-value of the material at the mean temperature from the calculated R-values. A system for non-destructive in-situ determination of the R-value of a material at a mean temperature comprises a housing defining a chamber, a temperature control system for heating and cooling the chamber between three or more steady-state temperatures, heat flux transducers, temperature sensors and a computing device from controlling the temperature control system and comprising a data acquisition system for recording measurements from the heat flux transducers and the temperature sensors.