## 7 Conclusions  
This study concludes that, in the case of a federation or a group of Smart Buildings, the strategy of using Fog Computing with IoT devices of the three types mentioned as (1) to (3) in Table 2, intelligently and sparingly at the Edge, is the best solution. It is also recommended to complement this strategy with the adoption of SDN by service providers and cloud vendors.  
Conversely, for standalone Smart Buildings with a limited number of properties per tower (estimated at 20-60 units), this study concludes that a strategy employing IEC and IoT devices of types (1) and (2) at the Edge, leveraging simpler technological solutions within this condominium category, represents the optimal approach. Generally, these isolated SBs are sensitive to operational costs and initial investments. The adoption of open SDN architecture by cloud providers maintains the consistency of this approach and should be strongly considered.  
The information gathered from field research and state-of-the-art literature on proprietary switches [11; 13] (e.g., Cisco Systems, Aruba and Fortinet) versus the costs of open source and OpenFlow SDN switches from various community manufacturers indicates that the latter are more cost-effective.  
Furthermore, the labor required is less specialized, as many professionals operate as freelancers in the SDN switch market, offering reduced implementation and maintenance costs.  
Additionally, the easy adoption of the international and open SDN standard mitigates the \"vendor lock-in\" problem, which tends to result in higher costs in the medium and long term due to the proprietary nature of closed technologies.  
NFV, in agreement with telecommunication companies, can also be adopted for both scenarios, resulting in reduced operational costs and technological advancement without requiring significant hardware and software reinvestment after a certain number of years following initial Smart Building implementation. Decision-making should consider the advent of 6G, 5G, 5G-IoT cellular networks and new fiber optic implementations within Smart Cities, which may introduce both innovative solutions and new challenges to the current landscape.  
The future challenge, in developing countries, will be to balance investments in innovative 6G, 5G-IoT, local manufacturing of IoT devices, SDN and NFV technologies associated with Fog and IEC. Effective service availability for enterprises, medium businesses and end users will be achieved through economies of scale coupled with innovation, leading to lower-cost solutions.  
A key challenge will be to extend this strategy and the scientific advancements presented in this study of SBs to a larger scale within Smart Cities, ideally coordinated through a public-private partnership leveraging the technological progress of emerging Smart Buildings within a specific geographical area.  
Conceptualization and methodology, M.C.; writing--original draft preparation, M.C.; writing--review and editing, M.C. and M.A.R.; funding acquisition, M.A.R. All authors have read and agreed to the published version of the manuscript.  
This research and the APC was partially funded by Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES), Brazil--Finance Code 001, and in part by the Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) under Grant 2022/10909-5. The authors thank Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) under Grant 404081/2023-1 **Institutional Review Board Statement**: Not applicable.  
**Informed Consent Statement**: Not applicable.  
**Data Availability Statement**: The raw data supporting the conclusions of this article will be made available by the authors on request.  
**Conflicts of Interest**: The authors declare no conflicts of interest.