EnergyPlus

EnergyPlus [51] is a modular-based code that is built upon the well-known models BLAST and DOE-2 [52]. It is a simulation engine that manipulates input and output in text-command formats. A heat-balance engine undertakes the calculation of loads at a user-specified time step, which is then passed to the building systems' simulation module at each time step. The systems' simulation module computes heating and cooling system and electrical system responses. This integrated solution ensures precise space temperature prediction, which is crucial for system design, occupant comfort, and air quality calculations. Integrated simulation provides possibilities to evaluate plausible system controls, moisture transfer through construction elements, radiant heating and cooling systems, and interzone airflow.

Tsikaloudaki et al. (2012) [53] used EnergyPlus to evaluate the cooling performance of a wide variety of geometrical, thermo-physical, and optical properties of windows. The maximum cooling loads were documented when windows' solar transmittance is high and thermal transmittance is low. It was demonstrated that in Mediterranean climates the combined high efficiency of transparent elements and controlled ventilation in office buildings reduce heat losses and ultimately result in higher cooling energy loads. Goia et al. [54] used EnergyPlus to develop a methodology for determining the optimal glazing percentage in a façade unit for low-energy office buildings. The investigation involved three alternative building design versions with different HVACs' efficiency. It was shown that, regardless of the orientation and building façade area, the optimal configuration corresponds to a transparent-area percentage ranging between 35% and 45% of the total façade area. Due to its fully accessible suites, it has been widely used for coupled Building Energy/Computational Fluid Dynamics (BES-CFD) simulations for the quantitative analysis of building energy performance, taking into account the external microclimate conditions, thus accounting better for local environmental effects in the vicinity of the buildings [55–57]. Due to its modular nature, it requires advanced knowledge of building physics as well as high computer skills, especially in case of complex physical systems such as those focusing particularly on indoor–outdoor interactions.

The DesignBuilder software [58] confronts the aforementioned barrier as it essentially represents a user-friendly version (in fact, with elegant graphical interface), including additional modules such as that of CFD computations for both indoor and outdoor airflow simulations. DesignBuilder software stands for a general purpose simulation engine allowing for energy analysis and automatic optimization for various building systems (HVAC, lighting, DHW), RES technologies, and construction materials, calculating additional key performance indicators such as thermal comfort (PMV, PPD), carbon and GHG emissions, and financial analysis. Thus, it serves for holistic decision-making strategies. In the framework of the IMPULSE project (Interreg MED 2014–2021), it has been used to prioritize retrofitting measures towards the gradual energy-upgrading plan for public buildings (in accordance with the EU directive 2012/27/EU) in the Municipality of Heraklion, Greece [59]. Among many applications for both practical and research purposes, it has been used to demonstrate proof of concept regarding energy-upgrading measures, for example, for reflective (cool) materials' applications [60,61]. Specifically, for PCM applications it has become evident that EnergyPlus contains numerical models much more accurate than those of other popular BES tools, such as TRNSYS [62]. The tool has been also used with success to prescribe retrofitting strategies, focused on the building envelope, for higher education buildings in Egypt [27], concluding with useful suggestions for design codes ensuring balance between thermal comfort and energy efficiency.
