Whole life-cycle carbon assessment of building retrofits with water-filled glass (WFG) secondary glazing

The existing building stock possesses a proportionally high impact on greenhouse gas emissions due to its low operational energy performance; retrofitting is a prominent strategy in many countries to help solve this, and as such is considered important to achieve a carbon neutral society. Among the energy retrofitting measures (ERMs), those impacting the performance of building envelopes are of primary relevance, especially ones that possess high Window-to-Wall Ratios (WWR) over 50%; these are predominantly found in office buildings built after 1960s. Here, the two dominant ERM strategies are to replace low performing elements, or to add secondary layers to the existing glass. This second strategy in particular is shown to present several benefits, however these are seldom considered and verified within a wider Life-Cycle Analysis (LCA). To this effect, this paper aims to quantify the savings achieved through the ERM of secondary layer addition to existing glazed facades, for a high WWR office building in cooling and heating dominated climate locations (Dubai, London, and New York). This is then evaluated against an LCA for each glazing ERM chosen, to assess how each retrofit affects the embodied carbon produced. Two base scenarios in each city have been simulated in TRNSYS (single and double glass cases), with three standard market options for layers addition (single, double, and water-filled glass). Water-filled Glass is introduced as a potential ERM for the first time, that utilizes a water layer to improve performance. The aim of this paper is to evaluate the holistic efficiency of different ERMs within the transparent building envelope.