In-Situ R-Value & Building Envelope Heat Flux Testing
FluxTeq large-area heat flux sensors are used in building science research to measure heat flow through walls, insulation systems, retrofit assemblies, thermal bridges, floors, ceilings, and other building envelope components. By combining heat flux measurements with indoor and outdoor temperature data, researchers can evaluate real-world U-values, R-values, thermal bridging effects, and building energy model accuracy under actual operating conditions.
Recommended Products:
Ultra-09
Ultra sensitive heat flux plate for high insulation, and extremely low heat flux resolution
PHFS-09e
Low profile sensor for in-situ building envelope heat flow.
FluxDAQ+
Multi-channel heat flux and temperature logging for field studies.
Why Heat Flux Sensors for In-Situ R-Value Testing?
Temperature alone does not tell you how much heat is actually moving through a wall, roof, floor, window, or insulation assembly. Two building surfaces can have similar temperatures while transferring very different amounts of heat depending on insulation levels, thermal bridging, solar exposure, air leakage, moisture, and construction details.
Heat flux sensors directly measure the rate of heat transfer through a surface. When paired with indoor and outdoor temperature measurements, this allows researchers and building scientists to calculate in-situ U-values and R-values, validate energy models, compare wall retrofit systems, identify thermal bridges, and quantify real-world building envelope performance.
For building science applications, direct heat flux measurement is especially useful for:
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in-situ R-value and U-value testing
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building envelope heat loss measurement
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wall retrofit performance monitoring
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thermal bridge detection and quantification
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insulation system comparison
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EnergyPlus, DOE-2, and building energy model validation
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façade, wall, floor, ceiling, and window heat flow studies
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long-term thermal and hygrothermal building monitoring
The studies summarized here were conducted by independent researchers. FluxTeq did not necessarily design, perform, or validate the experiments. These publications are provided as examples of how FluxTeq sensors and DAQ systems have been used in battery thermal research.
Wall Upgrades for Energy Retrofits: A Techno-Economic Study
PNNL / DOE Report, 2022
View Report: https://www.pnnl.gov/publications/wall-upgrades-energy-retrofits-techno-economic-study
Application: Wall retrofit performance monitoring and in-situ building envelope testing
Relevant sensor: PHFS-09e
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Summary:
This U.S. Department of Energy project evaluated wall retrofit strategies for older residential buildings, focusing on energy savings, moisture performance, constructability, and economics. The report notes that nearly 70% of U.S. residential housing stock was built before 1992, and that many older homes have little or no wall insulation, making wall retrofit performance a high-impact building science problem. The project tested 14 wall retrofit configurations and 2 baseline wall configurations at the University of Minnesota’s Cloquet Residential Research Facility.
FluxTeq PHFS-09e heat flux sensors were installed in the wall assemblies as part of the in-situ performance data collection system. The report lists the PHFS-09e as the heat flux sensor used alongside Type-T thermocouples, relative humidity sensors, and moisture-content sensors. The heat flux plate was located on the interior surface of the drywall, while other sensors measured temperatures and moisture conditions through the wall assembly.
View Journal Article: https://www.mdpi.com/2075-5309/12/2/176
Application: Building Envelope Testing, Thermal Bridging
Relevant FluxTeq product: PHFS-09e + FluxTeq DAQ+
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Summary:
This paper studied thermal bridging in Saudi Arabian residential buildings constructed with reinforced concrete frames and block in-fill walls. The researchers monitored three buildings in Riyadh representing different wall construction types: an uninsulated concrete block wall, an insulated concrete block wall, and a double-layer volcanic block wall with insulation. The buildings faced west and were exposed to intense afternoon/evening sun, making them useful for studying thermal bridging and solar radiation effects in hot climates.
The researchers used a PHFS-09e heat flux and surface temperature sensor produced by FluxTeq and recorded data with a FluxDAQ+ data logging system. Sensors were placed on concrete columns and in-fill wall sections to compare heat flow through bridged structural concrete elements versus insulated wall areas.
The paper found that heat loss across uninsulated cast-in-place structural concrete elements was more than double the heat loss across insulated wall portions. It also found that neglecting solar radiation on the west façade could produce errors greater than 50%, and that external insulation could reduce the thermal bridging impact by up to 73%.
Solutions for Exposed Structural Concrete Bridged Elements for a More Sustainable Concrete Construction in Hot Climates
Buildings, 2022
Accuracy of HVAC Load Predictions: Validation of EnergyPlus and DOE-2 using FLEXLAB Measurements
Lawrence Berkeley National Laboratory, 2020.
View Report: https://bies.lbl.gov/publications/accuracy-hvac-load-predictions
Application: Building energy model validation and surface heat flow measurement
Relevant sensor category: PHFS-09e
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Summary:
This Lawrence Berkeley National Laboratory report used measured performance data from the FLEXLAB test facility to validate heating and cooling load predictions from EnergyPlus, DOE-2.1e, and DOE-2.2. The study recorded detailed measurements including indoor temperatures, heat fluxes, HVAC air and water flow rates, and weather data, then compared measured results to building energy simulation outputs.
FluxTeq PHFS-09e heat flux meters were used for surface heat flow measurements. The sensor table lists “Heat flux meter, FluxTeq PHFS-09e” as the majority heat flux meter type, with approximately 20 sensors used to measure surface heat flow rate through walls, floor, ceiling, window glazing, frames, and mullions. Sensor data were sampled every second, then averaged into one-minute values for analysis.
The report found that EnergyPlus, DOE-2.1e, and DOE-2.2 produced broadly similar agreement with FLEXLAB measurements for conventional overhead mixing ventilation scenarios. The study reported average range-normalized root mean square errors of about 9–12%, showing the importance of high-quality measured data for validating simulation engines used in building design, code compliance, and energy retrofit analysis.