The implementation of BIST has all the benefits and co-benefits related to the use of renewable sources, including: 

• Health 

• Improved air quality - reducing CO2 emissions and air pollutants related to the combustion of fossil fuels 

• Social: 

• Reduce energy poverty – reducing the dependence from the grid thus reducing the cost 

• Economy 

• Growth of local economy and job creation 

• Energy security – increasing the self-production of energy and alleviating the peak demand of the grid 

• Enhanced attractiveness of the cities – BIST can improve building aesthetics 

• Climate and geography: There are no specific constraints for the installation of BIST systems. Nevertheless, the cost-benefits are higher in locations with high solar radiation and high incidence angles. Another factor that should be taken into account is the wind exposure that can highly affect the heat losses of the BIST system. 

• Technical aspects/infrastructure: Constraints in the building architecture and also in existing heating systems (in refurbishment cases) can be the main barrier for the BIST integration. The potential of energy generated by the BIST is proportional to the? surface available that can have different perspective in the case of new construction or refurbishment. The presence of obstacles (e.g., windows, chimneys, and stairwells) causes a reduction of useful spaces for BIST. Shading should be also taken into account that could decrease the system performance. BIST should offer mechanical and structural integrity and protections with all weather conditions. BIST that integrates thermal energy storage should also have enough space for the installation.   

• Aesthetics aspects: In order to be architecturally and social accepted, BIST must be integrated naturally and be consistent to the context of the building. The design should be architecturally pleasing with a good composition of colours and materials. The size should fit the harmony and combination of the building components [7].   

• Policy and regulatory/legal framework: Generally, the integration solar systems is supported by different direct policies [8]. These include targets such as the aim to reach the share of renewables that nowadays in Europe is proposed to be increased to 45% under the Fit for 55 package including as well a solar rooftop initiative [9]. Moreover, the installation of BIST must comply with building codes and standards, which in most cases were developed for conventional envelope elements.  

Approach: Consult scientific literature, grey literature (project reports, reports), specifically the repository of EU-funded R&I projects, and other research projects, case studies, application, as required. 

Effort: Be concise, bullet points (approx. 800 words). 

The implementation of BIST follows the most common barriers related to solar collectors which are mainly [8,10]: 

• High investment cost compared to other alternatives (electric heaters, gas boilers) 

• Difficulty access to finance 

• Slow moving construction sector 

• Lack of regulatory framework that can guarantee quality and reliable operation of solar thermal systems 

• Burdensome authorization process for new capacity installation 

• Technical limitation for solar cooling systems  

• Low level of awareness from households  

Moreover, BIST suffers from: 

• Aesthetic concerns 

• Physical space/surface constrains 

• Lack of adequate test methods and regulatory gaps 

• Lack of specific policies 

It is important to highlight that BIST is part of the building functionality and if they are dismounted from the building, the adjacent component will be affected and will have to be replaced partly or totally by an another component [1]. 

The main drawbacks of the integration of BIST systems include: 

• Cost and maintenance  

• Fragility of glass components 

• Reflections from the glass cover can cause undesirable glare 

• Overheating – affects the durability of BIST and safety 

The integration of BIST has a direct effect in decreasing the total primary energy consumption in buildings that can be potentially reduced up to 21% with up to 60% of energy saving to produce hot water and 40% to space heating and cooling [6].  

The integration of BIST contributes to increasing the generation of energy capacity of solar thermal which in Europe corresponds to 37.7 GWth [4] installed in the year 2020. According to [5], the installed capacity of solar thermal in Europe has the potential to reach 140 GWth in 2030 

Implementations should follow the technical requirements and standards included in national and local legislations. In Europe, the currently available standards for construction components are [2]: Regulation 305/2011, European Technical Approval Guidelines (ETAG), the Construction Products Directive (CPD) and Construction Products Regulation (CPR), Directive on the Energy Performance of Buildings (EPBD).  

The availability of skilled workers is critical and training programmes and certification schemes are necessary to promote local employment. 

 In order to promote this solution the following instruments might be considered: 

• energy audits 

• certification and labelling 

• infodays 

• workshops 

• awareness campaigns 

• promotional campaigns 

• grants/subsidies 

• loans/soft loans  

• incentives/disincentives 

• taxation  

• integrated action plans 

• decarbonisation plans for industry 

• building codes/standards 

• energy supplier obligations 

• smart readiness indicator 

• provision of energy efficient products and services 

• GHG scenario modelling 

• LCA/LCC