Innovations
Innovation: Water-filled glass (WFG) can transform building design and efficiency as part of a broader heating system
It’s widely acknowledged that the heating and cooling of buildings are not only costly but also significantly contribute to carbon emissions. The UK Green Building Council reports that approximately 40% of the UK’s carbon footprint is attributed to the built environment, with heating being responsible for 10% of this figure.
Dr Matyas Gutai emphasizes the importance of enhancing windows to address our carbon challenges. Although windows cover a relatively small portion of a building’s surface, they offer far less insulation than typical wall areas, and minor improvements can result in energy savings of up to 25% for an entire building. An expert in the School of Architecture, Building and Civil Engineering, Dr Gutai has identified a more energy-efficient material than existing options, including double and triple-glazed windows: water.
Having devoted over ten years to this research, Dr Gutai’s latest work, published in Elsevier’s Energy and Buildings Journal in partnership with Dr Abolfazl Kheybari from the University of Kaiserslautern, shows how water-filled glass (WFG) can transform building design and efficiency as part of a broader heating system. The study demonstrates that WFG systems are effective in various climates, maintaining cool temperatures in warm regions and warmth in cooler areas, all without extra energy input, thereby offering significant potential in reducing carbon emissions.
Water-filled glass involves encasing a layer of water between two glass panels, which remains virtually invisible. Dr Gutai conceived this idea during his PhD studies at the University of Tokyo, inspired by the thermal properties of Japanese outdoor baths, or ‘rotenburo’. He developed this concept into a functional design, leading to the construction of two prototype buildings in Hungary and Taiwan that incorporate WFG within their larger mechanical systems.
The WFG system connects water-filled window panels to a storage tank via concealed pipes in the walls, allowing fluid circulation. This design enables the ‘Water Houses’ to self-regulate their temperature for most of the year without additional energy sources. In warm conditions, the water absorbs heat, which is then stored in the tank, either in the foundations or elsewhere in the building. When temperatures drop, the stored heat can be redistributed to warm the building, similar to central heating, or used for hot water. This process is more energy-efficient than conventional HVAC systems due to the lower energy requirements for water absorption and pumping.
Additionally, this technology offers advantages in acoustics, reduced need for shading, and aesthetic appeal, as there is no need to tint the glass for energy efficiency. Dr Gutai has further enhanced the system by incorporating a heat pump that adjusts the water temperature according to the season, a feature detailed in his latest research paper.
Joining Loughborough University in 2017, Dr Gutai has utilized data from the Water Houses to develop a simulation system assessing the energy performance of such structures. His latest publication compares the WFG system (with a heat pump) against standard building heating solutions (like gas heating and air conditioning).
Focusing on the annual energy consumption of a typical office space with a glazed façade facing south in the northern hemisphere, Dr Gutai conducted simulations in 13 cities across various climate zones, excluding polar regions. He compared the WFG system to double glazed windows with low-e coating and triple glazed windows filled with argon gas.
Key findings indicate:
-The WFG system significantly improves energy performance through water absorption.
-It effectively reduces heating and cooling demands, minimizing daily and seasonal fluctuations.
-Energy savings in inhabited regions range from 47%-72% compared to double glazed windows and 34%-61% compared to triple glazed windows.
The study also suggests that focusing on enhancing solar absorption rather than insulation could lead to greater energy savings with current glass technologies. Dr Gutai highlights the transformative potential of WFG, turning glass from a building liability into a sustainable construction opportunity. He emphasizes the benefits of a holistic approach to building components, where, for instance, excess heat in one part of a building can be used beneficially elsewhere.
Dr Gutai is now working towards commercializing this technology and is collaborating with academic and industrial partners. He plans to extend his research to compare WFG with dynamic glazing and to evaluate its life-cycle impact and thermal comfort.
Dr Gutai’s latest study, titled ‘Energy consumption of water-filled glass (WFG) hybrid building envelope’, can be found viewed at: https://www.sciencedirect.com/science/article/abs/pii/S0378778819328944?dgcid=author
Why it matters: All the talk has been about triple-glazing to improve the performance of glazing. Water-filled glazing is a very viable alternative and has produced some impressive results. The big question is its commercial viability. It just takes one company to invest and take it forward…
