| With recent emphasis on reducing building energy consumption, tools are needed that can determine the overall performance of building thermal envelopes in a manner that is accurate, efficient, and accessible. Two such methods---one experimental and one numerical---were developed for the evaluation and optimization of building thermal envelopes at the University of Wisconsin- Madison.;A Rotatable Guarded Hot Box (RGHB) apparatus was designed and constructed for the large-scale thermal testing of post-frame building envelope designs. In addition to conducting standard thermal performance tests in accordance with ASTM C1363, the apparatus---capable of testing a wall or roof specimen up to 2.9 x 3.8 m---was designed to simulate the effects of air infiltration through the application of a static pressure differential across the test specimen. Utilizing a cable winch system and centralized pivot point, the entire apparatus may be rotated 360 degrees about its horizontal axis to test wall or roof specimens at any orientation. Using this apparatus, the thermal effect of various envelope design changes such as structural component placement and orientation, insulation type and geometry, and the inclusion and placement of air barriers may be studied. This apparatus employs an automated computer control system that acquires and stores temperature, pressure, air speed, and relative humidity data; varies heater and fan output; calculates and records key variables; and determines the completion of experimental objectives. Using this system, it is possible to expedite the conduction of accurate thermal experiments with a minimum of human interaction.;The thermal performance of nine post-frame thermal envelopes was studied and optimized using a computational fluid dynamics model validated experimentally by the rotatable guarded hot box. In addition to providing thermal performance values for typical wall designs, this study proposed a new wall design that greatly increased thermal performance without sacrificing material efficiency. Study variables included structural geometry, level of insulation, and the presence and placement of radiant barriers. To reduce computational demand, modeling was primarily conducted using an area-weighted average of two-dimensional slices to represent three-dimensional assemblies. After modeling a portion of the assembly in three dimensions and comparing it with its two-dimensional counterpart, this simplification was found to result in less than a 6.7% error. Significant error (up to 57%); however, was determined to be integral to the simplifying assumptions commonly used by building designers, especially in envelopes common to the agricultural industry. This error was estimated to underpredict energy costs for a 2,200 m2 cold-storage warehouse in Wisconsin by approximately ;The combination of these two distinct methods allows investigation of the effects that a wide array of factors have on the thermal performance of a building envelope. Through the investigation of these individual factors, thermal envelopes as a whole may be optimized for sustainability, based on a balance of the efficient use of energy, material, and labor. |
