The Thermal Façade Lab (Figure 1) is a pair of identical building units installed at the south end of the West Mall Building at the University of Texas School of Architecture in Austin, Texas. These units are constructed using highly insulated shells (the walls, ceilings, and floors have an insulation rating of > R60 (IPS) with a south-facing façade. These labs are designed to allow for the testing of façade elements - such a glazing, shading, or decorative/weather protective shells - and their impact on building energy use. However, they also can be used for other energy or indoor air quality studies. Below is a list of potential studies that can be performed using the Thermal Façade Lab.
The façade system of a building can have a significant impact on the energy use of buildings. Façade systems act both as weather resistive components of a structure, shielding the structure and occupants from heat, cold, rain, sun, and other weather processes, and decorative elements. Striking the right balance of cost, effectiveness, and energy use can be a difficult proposition for façade designers. The Thermal Labs offer a platform for the testing and validation of novel and creative façade systems and their impact on overall building energy use. The wide range of sensors that are compatible with the Thermal Lab data acquisition system, as well as the ability to remotely monitor and control the instrumentation, make the Thermal Labs an ideal platform for such research.
Ongoing advancements in window technologies designed to maximize daylighting while reducing thermal energy loads require real-world validation. The Thermal Façade labs offer a platform where the impacts of changes in window design can be tested under actual weather conditions. The two Thermal Façade Labs allows for the testing of new windows against an existing standard under identical weather scenarios, giving useful feedback to manufacturers and developers of these products. The highly instrumented facility - complete with its own weather station - make the Thermal Façade Lab a natural venue for such validations. Potential studies include active window systems, where the light or energy passing properties of the windows can be adjusted by the user, or by specialized controls designed to maximize energy savings.
The impact of both passive and active shading systems can be tested using the Thermal Façade labs. One such study into passive low-protruding shading systems by UT Student Stefan Bader produced a novel design that was tested at the Thermal Façade labs, as shown in Figure 2. This system clung closely to the windows, limiting both manufacturing costs and visual impact. Further studies utilizing actively controlled shading systems have been suggested as a means to maximize energy savings related to both lighting and air conditioning applications.
Phase Change Materials (HVAC Systems)
The Thermal Façade lab has incorporated in its environmental control systems the ability to utilize both passive and active thermal storage using PCMs, or Phase Change Materials. Building products or elements containing PCMs – such as wallboard, floor and ceiling tiles, or trombe walls – may be utilized within the Thermal Façade lab interior spaces. The extensive instrumentation capabilities of the labs allow them to monitor energy consumption (both thermal and electrical) so as to determine the true impact of these technologies while experiencing real-world weather and HVAC conditions. In addition, the Thermal Façade lab HVAC system – which is based on a chilled water distribution system very similar to that used in many large commercial buildings – includes a thermal storage tank that is capable of acting as a sensible thermal storage system using chilled water, or as a latent thermal storage system using encapsulated PCMs. An extensive system of controls and instrumentation allow for the discharge and charge of the thermal storage system as determined by user-provided programming.
Ventilation Systems and Protocols
As buildings become more energy efficient, they become tighter; this results in an increase in the concentration of some pollutants in the interior environment. In such cases a ventilation system is required to bring in fresh outdoor air. However, ventilation replaces conditioned air with unconditioned air, adding to the HVAC load of the building. The Thermal Façade Labs contain a ventilation system that is capable of monitoring airflow volumes, temperature, and humidity so as to accurately measure the thermal impact of the incoming fresh air on the HVAC system. In addition, these measurements can be confirmed by the HVAC system capability to measure total system load. These instrumentation and control systems allow for the study of devices such as high-efficiency heat exchangers, or protocols, such as the off-peak ventilation schemes described in the ASHRAE 62.2 standard for ventilation and indoor air quality.
The centralized control system of the Thermal Façade labs allows for modification using standard National Instruments controllers and LabVIEW software. The current system uses a National Instruments MyRIO controller, a low-cost but highly capable controller available directly to students at a significantly reduced cost. This allows students to obtain their own controller for program design and testing, permitting them to perfect each iteration of their control system independently of the lab and prior to implementation. In addition, expansion of the system to control more complicated designs is possible through the use of larger National Instruments RIO system. This makes the Thermal lab an excellent platform for the development of HVAC and environmental control systems
These are only a summary of the studies possible using the Thermal Façade labs. Their advanced control and instrumentation systems make them an ideal platform for studies involving façade technologies or building thermal control system. For more information, or to inquire as to the availability of the labs for research projects, please contact the Thermal Façade Lab coordinator
Thermal Lab Statistics
The Thermal Labs are located in the School of Architecture (UTSoA) on the Austin campus, at a latitude of 30,3° N and a longitude of 97,7° W, elevated approximately 6 m above street level. Their south façade is, at 11°, slightly oriented towards the east. The two labs are representatives of typical single office rooms. The only opening is on the south façade with a glazing amount of about 92%. It can be modified or replaced to test different façade concepts. The other envelope – three walls, floor, ceiling – are highly insulated and contain almost no thermal mass.
The Thermal Labs are equipped with a full instruNet variable voltage measurement system which can record from a variety of sensors. The main sensors used for analysis are thermresistor point sensors which measure temperature in a 3x3 matrix on each surface of the Thermal Lab. Within the lab, variables such as lighting control, glazing control, architectural facade control, and mechanical system control can be manipulated depending on experiment scope.
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The air is supplied through two exhaust openings closest to the south wall in order to release hot or cold air onto the upper part of the window, reducing temperature gains and losses through the glazing. The cooling system consists of a chiller, which cools a loop of single-phase chilled water-ethylene glycol mix. To provide cooling, one hundred percent return air is circulated within the lab fan cooling coil unit at a constant rate.