Abstract

A solution for lowering cooling loads in hot regions involves improving building envelopes with high-performance window retrofits, as windows are a large source of heat gain. Unfortunately, high-performance windows are 3-5 times more expensive than plain glass windows. A recent low-cost retrofit strategy to cut cooling loads proposed adding a second layer of polycarbonate (PC) sheet decorated with stained-glass patterns using 3-D printing. This work evaluates the feasibility, energy efficiency, and cost-saving potential of this approach. Case studies of New Delhi, India, and Rome, Italy, are evaluated for a range of retrofit strategies. Spectral transmissivities of colored PC-stained glass areas are quantified, and solar heat gain coefficients (SHGC) for complex windows are determined for the whole window thermal performance assessment. Based on the validation, the SHGC and heat transfer coefficient (U-value) are calculated and combined with the meteorological datasets to simulated validated house model. The results show that the approach can decrease cooling loads to the point that a heat pump can be downsized from a 3.5-ton to a 3-ton AC unit in New Delhi. In Rome, the load is also reduced. In New Delhi, the payback period is 3.3 to 3.4 years and has an internal rate of return (IRR) from 51.5% to 58.8%. The IRR in Rome, however, is lower because of higher material prices and a more modest cooling load. The proposed methodology and case studies demonstrate the potential of colored PC window retrofits with custom-stained-glass decorations to reduce cooling costs economically. 1

Keywords

energy conservation // windows // distributed manufacturing // cooling load // building energy modeling // additive manufacturing

Resources and links

• 📝 Full text (preprint version) 2
• 🛠️ OSF Repository (3D models and dataset) 3