**5. Conclusions**

This paper has studied a model to assess innovative building envelopes' energy performance, such as water flow glazing (WFG), the system equations for load calculation, and the relationships with steady and transient parameters. Some of the magnitudes can be measured accurately in the prototype. The presented tool has been developed and tested by the authors. Details of the prototype and the on-site measures have been used to validate the tool. The analysis included a free-floating temperature regime and a cooling system with simple logic to keep the prototype within a comfort range. Results included simulated indoor air and glazing temperatures along with the potential final energy savings.

1. When the WFG cabin's interior temperature was below the exterior temperature, the WFG facade cooled down the room. As the "Peltier" device was not in operation over 2019, it can be concluded that WFG working on a free-floating temperature regime, without auxiliary energy systems, results in smaller indoor temperature fluctuations.

2. Circulating water increased the temperature gap between external and internal glass panes. The outer pane reached temperatures above 41 ◦C, while the maximum surface temperature on the inner pane was 34 ◦C. The reference glazing showed a smaller gap between outer pane (41 ◦C) and inner pane (38 ◦C). The reduction of radiant temperature of indoor envelopes can improve the occupant's comfort.

3. The damping effect on the WFG cabin's temperature is shown in Figure 12. The WFG system provided the facade with thermal inertia, and the cabin did not suffer large thermal oscillations between day and night. This effect can increase the thermal comfort inside the building and reduce energy consumption.

4. The WFG increased the thermal inertia of the facade. Once the maximum temperature was reached, the interior of the WFG cabin cooled down more slowly than the Reference cabin did.

There was a good agreement between the simulation and the real data from the prototype. MEs and MPEs of the indoor temperature in the WFG cabin, were lower than 1.2 ◦C and 5.5%, respectively. The simulation results of the Reference cabin were more accurate because the boundary conditions were more suitable to predict.

The weather and indoor conditions impact the efficiency coefficients of heat pumps. The EER values of the cooling systems were evaluated for different combinations of indoor and outdoor conditions.

Ground source heat pumps (GCHP) coupled with borehole heat exchangers in a closed loop are very effective and make the most of the near-constant ground temperature over the year.

Finally, if the electricity is supplied from solar cells, it is possible to use a renewable and CO2 free energy source to provide thermal comfort.

**Author Contributions:** Conceptualization, B.M.S., F.d.A.G., J.A.H.R.; methodology, B.M.S., F.d.A.G.; software, J.A.H.R.; formal analysis, B.M.S., F.d.A.G.; data curation, J.A.H.R.; writing—original draft preparation, J.A.H.R.; writing—review and editing, F.d.A.G., B.L.A.; visualization, B.M.S., F.d.A.G., B.L.A.; supervision, J.A.H.R., B.L.A.; project administration, B.M.S.; funding acquisition, F.d.A.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** This article has been funded by KSC Faculty Development Grant (Keene State College, New Hamshire, USA).

**Acknowledgments:** This work was supported by program Horizon 2020-EU.3.3.1: Reducing energy consumption and carbon footprint by smart and sustainable use, project Ref. 680441 InDeWaG: Industrialized Development of Water Flow Glazing Systems.

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