Thermal comfort of standard and advanced glazed building envelopes

The characteristics of building envelopes impose significant impacts on indoor thermal comfort, especially for buildings that possess higher portions of glazing. As a result, the overall Indoor Environmental Quality (IEQ) is also largely controlled by the glazing scenario. Recent studies present three strategies to mitigate this aspect, by either i) improving the U-value with additional glass layers (insulation-based), ii) utilizing shading devices, or iii) changing the transparency or reflectance of glass (radiation control). In this study, Water-filled Glass (WFG) is presented as a potential fourth strategy. WFG is an innovative technology that utilizes a water layer within an insulated glass unit, to help improve the energy performance of the glazing. Current research primarily focuses on the energy consumption of WFG technology, and its potential to reduce both operational and embodied carbon. However, the potential impact on the thermal comfort of buildings, due to the thermal mass, absorption and radiant heating–cooling properties of its water layer have not yet been analysed in detail.

To build on this, this paper provides comparisons of various standard and advanced glazing technologies clustered in the above strategies, to assess the impact of glazing choice on indoor thermal comfort. This is conducted for both an office and a sunroom scenario using the Analytical Comfort Zone PMV (SolarCal) Method. Seven conventional glass technologies across nine locations were measured, to represent all major inhabited climate regions (Koppen-Geiger ¨ A-D).

Results show that WFG-like technologies can provide the highest amount of thermal comfort in up to eight out of nine climates; depending on the structure and in free-floating conditions, up to 26 % thermally comfortable periods can be achieved over an entire year. When this is compared to the base case, an additional 19 % comfortable periods are created. For hotter and more tropical climates (Af, BSk, Bwh), solar-gain focused techniques often function best, such as electrochromic and double glazing with permanent shading.

This study also highlights the importance of thermal mass in glass structures, as well as the advantage of dynamic fluid mass over a static one. The results show that by utilizing WFG, up to 64–145 kWh of energy can also potentially be absorbed annually. In addition to this, this glazing technology offers warmer discomfort periods for many climates during colder seasons. Whilst this initially may seem undesirable, it offers an op?portunity for the adoption of passive strategies, as well as heat redistribution to neighbouring thermal spaces, to potentially reduce overall energy usage at the building level.