Back to knowledge

BIST (Building Integrated Solar Thermal)

Building Integrated Solar Thermal (BIST) can be considered a typology of solar thermal collectors, which are directly integrated to the building and used to convert solar radiation into useful heat that can be used in different applications.  


BIST typologies can be classified using different criteria, most commonly by the heat transfer fluid used in the solar thermal system which can be air, water or refrigerant. BIST using air as heat transfer fluid can be used for example to pre-heat the air passing through a heat recovery ventilator or an air coil of a heat pump [2]. The air-based BIST consists of an air gap between a glazed or opaque cover (or also PV panels) and the building fabric. Air-based BIST has the main advantage of avoiding freezing problems and corrosion, low cost, and simple structure. Water-based BIST can be employed in a building to produce domestic hot water or space heating. In this case, flat plate collectors are the main technology used but evacuated tubes can also be employed due to the higher efficiency but with the disadvantage of fragility.   

Refrigerant as heat transfer fluid can be used in systems coupled with heat pumps and PV/thermal systems. In this case, the BIST can operate as the evaporator of the heat pump increasing the efficiency using the rejection heat from the PV/thermal systems.  

BIST can be made in different designs to be integrated as architectural element that can be integrated in roofs, façades, windows, or used as shading element or to substitute frames and balustrades [3].  

Source: https://siko.at/  


The integration of BIST has a strong influence on the building aesthetics, therefore colour and the shape, and support elements have a fundamental role. Moreover, the integration of solar thermal elements  must offer structural integrity, protection from wind, rain and moisture [3]




BIST systems are based on solar thermal technology which is already mature and available in the market (TRL 9). BIST can be used for domestic applications, to produce domestic hot water, space heating/cooling, air ventilation, and they are able to operate in different range of temperatures. Different examples of BIST systems installed in buildings are available in the database published and created in the framework of IEA-SHC Task 39. 

Comments ()




Under license CC BY-NC-SA
This license allows reusers to distribute, remix, adapt, and build upon the material in any medium or format for noncommercial purposes only, and only so long as attribution is given to the creator. If you remix, adapt, or build upon the material, you must license the modified material under identical terms.