Experimental Thermal Resistance Comparison of a Reflective Insulation in Vertical and Horizontal Furred Airspace Orientations Using a Guarded Hot Box
Bibliographic record
Abstract
Typical analyses of heat transfer across building envelopes consist of determining the thermal resistance of the assembly. The thermal resistance, or R value, is determined through test methods, calculation methods, or numerical simulations. In complex or novel wall assembly configurations, thermal resistance is required to be determined with experiments that use a guarded hot box (GHB) test apparatus according to ASTM C1363, Standard Test Method for Thermal Performance of Building Materials and Envelope Assemblies by Means of a Hot Box Apparatus. One scenario in which complex heat transfer occurs is in a furred airspace in contact with a low emissivity, as the combined effects of natural convection and radiation dominate the heat transfer across the space. Convection and radiation heat‐transfer effects are much more sensitive to the variation in surface temperatures, orientation, and aspect ratio of the airspace. This paper presents the results of ASTM C1363 GHB tests of a full‐scale (8 ft by 8 ft [2.44 m by 2.44 m]) wall assembly containing a furred airspace, with one surface having low emissivity in two configurations. The first configuration is with ¾‐in. (19‐mm)‐depth strapping oriented vertically and spaced at 24 in. (0.61 m.) on center, creating four identical furred airspace cavities approximately 8 ft high by 24 in. wide. The second configuration consists of rotating the same wall assembly by 90°, creating four identical horizontally oriented furred airspace cavities. Each configuration was tested for three exterior temperature conditions: −20°C, −25°C, and −30°C—all with an indoor temperature of 21°C. Additionally, the experimental results were compared with results of the ISO 6946 Annex B.2 calculation method. The results from the tests did not show a significant difference in thermal resistance results between either the exterior temperature differences or when comparing the effects of airspace orientation. This highlights some of the challenges when trying to differentiate small differences between wall assemblies with GHB testing, especially when the experimental uncertainty is considered.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".