Fenestration of today and tomorrow: A state-of-the-art review and future research opportunities

Abstract

Fenestration of today is continuously being developed into the fenestration of tomorrow, hence offering a steadily increase of daylight and solar energy utilization and control, and at the same time providing a necessary climate screen with a satisfactory thermal comfort. Within this work a state-of-the-art market review of the best performing fenestration products has been carried out, along with an overview of possible future research opportunities for the fenestration industry. The focus of the market review was low thermal transmittance (Uvalue). The lowest centre-of-glass U g -values found was 0.28 W/(m 2 K) and 0.30 W/(m 2 K), which was from a suspended coating glazing product and an aerogel glazing product, respectively. However, the majority of high performance products found were triple glazed. The lowest frame U-value was 0.61 W/(m 2 K). Vacuum glazing, smart windows, solar cell glazing, window frames, self-cleaning glazing, low-emissivity coatings and spacers were also reviewed, thus also representing possibilities for controlling and harvesting the solar radiation energy. Currently, vacuum glazing, new spacer materials and solutions, electrochromic windows and aerogel glazing seem to have the largest potential for improving the thermal performance and daylight and solar properties in fenestration products. Aerogel glazing has the lowest potential U-values, ~ 0.1 W/(m 2 K), but requires further work to improve the visible transmittance. Electrochromic vaccum glazing and evacuated aerogel glazing are two vacuum related solutions which have a large potential. There may also be opportunities for completely new material innovations which could revolutionize the fenestration industry.

Self-cleaning glazing products: A state-of-the-art review and future research pathways

“…Because, although the product is advertised as self-cleaning, cleaning is still needed, as earlier studies have claimed [3]. The dirt and dust that is attached to the glass only require water to wash off, thus no harsh cleaning chemicals or detergents are necessary, or applicable for that matter.…”

“…However, somewhat more frequent cleaning will probably solve this challenge. Finally, even though these factory-finished glazing products are advertised as self-cleaning, they do need some occasional rinsing to maintain a clear and clean surface [3].…”

“…anti-reflection and lowemissivity coatings on windows, which make up multifunctional products [3], one could believe that applying the technology from self-cleaning products onto, say, smart windows, building integrated photovoltaics (BIPV) or solar cells in general, would be possible and probably have a considerable positive effect too.…”

“…Nonetheless, if the transmission is affected or not, a self-cleaning surface like the one presented in Figure 9, might be applicaple to fenestration products made of e.g. aerogel, which already is in use as semi-transparent or translucent walls and fasçades, or other application areas that does not require complete transparency as regular glass [3,28].…”

“…However, the self-cleaning glasses had some remaining organic deposits, which were firmly bonded to the glass surface and were not washed off without human intervention. Moreover, another study, by Jelle et al [3], emphasizes that some maintenance, due to fastened organic or inorganic dirt, will be necessary with self-cleaning products regardless of their self-cleaning nature, though maybe not as frequent as with ordinary windows. Consequently, the self-cleaning windows may therefore also have a possible positive environmental impact, as due to less cleaning the use of chemical cleaners is reduced accordingly, which otherwise might have been spilled into the ground.…”