**5. Conclusions**

In this paper research on energy efficiency of the glazed BIPV façade structure with forced ventilated air gap is presented. Today, BIPV is considered to be one of the most important technologies by which, especially in the urban environment, the standards for the nearly or even zero energy buildings can be achieved. The studied BIPV element is designed as a modular unit that can be used in new, and with even greater advantages, in renovated buildings. The energy efficiency indicators were defined for each of the solar energy utilization modes—electricity production, energy savings due to decreased transmission heat losses and due to decreasing ventilation heat losses by preheating air for space ventilation. Results based on all-winter season experimental results had shown that up to 10% of daily solar radiation could be utilized for electricity and heat supply while preheating of the air utilizes up to 75% of daily received solar radiation. In the case of no clear sky conditions (low daily solar radiation) the efficiency of heat utilization increases further due to the dynamic thermal insulation effect. This are general figures. For day-to-day analyses in different climate conditions, the multi-parametric regression models were developed.

In follow-up research the impact of orientation of the BIPV façade structure with forced ventilated air gap will be studied and multi-parametric models developed, which will consider the thermal transmittance of the opaque envelope wall as an independent variable. The study of the impact of the other techniques for decreasing the PV cell temperature, like phase change materials, will also be interesting.

**Author Contributions:** Conceptualization, S.M., C.A., and S.D.; methodology, S.M.; validation, S.D., C.A., and L.P.; writing—original draft preparation, S.D. and C.A.; writing—review and editing, S.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** The authors acknowledge the financial support from the Slovenian Research Agency (research core funding No. P2-0223 (C)).

**Conflicts of Interest:** The authors declare no conflict of interest.
