Glazed building elements are a popular method in architecture for letting light into a building. This makes better use of environmentally friendly daylight, and less artificial lighting is needed. However, in order to maximise this advantage, the glass elements should preferably be used to construct entire walls for the building envelope, which requires that the elements have effective thermal insulation and can bear a certain load – a combination that has not been available on the market in this way until now.
Both requirements fulfilled: highly insulating and translucent
Silicate aerogels are high-performance thermal insulation materials that are becoming increasingly popular in the building sector. The most common are opaque insulation mats and plasters. Empa researcher Jannis Wernery and his colleagues from the “Building Energy Materials and Components” department already had the idea in 2017 to integrate the insulating material directly into a building block and presented a new type of brick filled with aerogel, the so-called “Aerobrick”. Thanks to its excellent thermal insulation, this brick saves heating costs – without the need for an additional insulation layer on the masonry.
However, aerogel can also be almost transparent, which enables a translucent, insulating building system. To take advantage of this and further improve the insulating performance of the “aerobrick”, Wernery, Michal Ganobjak and Co. developed a new type of modular component based on float glass and silicate aerogel granulate that combines both properties – it is translucent and thermally insulating: the aerogel glass block.
The glass blocks filled with translucent aerogel granulate allow the construction of aesthetically pleasing and even load-bearing façade elements that allow daylight to enter over a large area. The Empa researchers achieved this combination of strength, insulation and light transmission by using staggered spacers between the glass panes within the glass block, which ensure static stability with minimal heat transmission.
The glass block has a measured thermal conductivity of 53 mW/(m∙K) and a compressive strength of almost 45 MPa. This is the highest insulating performance of a brick to be found in the technical literature, let alone on the market. At the same time, there is also the property of light transmission.
Multiple applications in view
The aerogel glass block is suitable for applications in which there are simultaneous requirements for high daylight input, glare protection and privacy protection, for example in offices, libraries and museums. An important aspect here is that a building envelope made of such glass blocks couples the inside of the building with the outside in terms of daylight. This can have a positive effect on the daily rhythm of the building users. Possible applications include:
- Rooms that should not have a line of sight to the outside, for example for reasons of privacy, security or to avoid disturbances, but should still allow diffuse daylight into the interior, such as libraries, galleries, museums, foyers, offices, staircase cores, gymnasiums, multi-purpose halls, residential buildings or art workshops.
- Spaces where daylight is necessary for a healthy circadian rhythm, such as dormitories, hospitals and sanatoria, but also zoos, stables and animal breeding facilities up to greenhouses
- Places where a maximum of daylight is to be brought in and space is to be saved, for example in densely built-up city quarters with high-rise buildings and many city apartments
- Architectural elements such as Trombe walls in solar architecture, courtyards or atriums that generate heat from the infrared radiation of sunlight
An analysis of material costs shows that the insulating glass block can be quite competitive in such applications. The glass block thus offers architecture new design possibilities for more daylight in buildings – both for new buildings and for renovations. The researchers have now applied for a patent for the aerogel glass block and are looking for possible industrial partners.
