# BEST--Building Energy-Saving Tool for Sustainable Residential Buildings
## 2 Materials and Methods
### BEST Tool Description  
Users can access the tool via the internet using a browser as an interface; thus no specific hardware or software requirements are necessary. A simple internet connection and a browser are sufficient to fill in the data and run the calculation engine that generates the results.  
The simplified interface allows for the description of building characteristics and their building systems in order to perform quick assessments of the potential interventions for the refurbishment of the opaque envelope of the residential building stock.  
The BEST simulation tool was designed for application in the assessment of energy efficiency interventions for residential buildings, classified as follows:  
* E.1 (1)--Residential buildings with continuous occupancy (e.g., dwellings, boarding schools, convents, penitentiaries, barracks);
* E.1 (2)--Residential buildings with intermittent occupancy (e.g., vacation homes and similar structures).  
The computational tool aims to combine the simplicity of static methods with the accuracy of dynamic simulations, integrating additional functionalities to assess investment costs and their economic return, also considering the incentive schemes currently in force in Italy. For this reason, a simplified dynamic simulation approach was adopted, employing a single thermal zone to estimate the building's annual energy consumption in both electrical and thermal terms.  
The \"simplified dynamic simulation\" implemented in the BEST tool is based on the Italian technical standards UNI/TS 11300 (Parts 1, 2, and 4). These standards define the underlying assumptions and boundary conditions, including standardized climatic data, internal conditions (such as setpoint temperatures and internal gains), operational schedules, building envelope characteristics, ventilation rates, and system efficiencies. The approach can be described as a quasi-steady-state model applied over discrete time steps, rather than a detailed transient simulation.  
Regarding the climatic zone, one was selected arbitrarily for the purpose of the simulation. Given the objective of the study and the standardized nature of the input parameters, the specific choice of climatic zone does not substantially affect the methodological outcomes, or the validity of the comparative analysis carried out by the tool.  
The BEST tool supports simulations for all Italian climatic zones, as defined by national regulations. The UNI/TS 11300 standards incorporate climate-specific parameters for each of the six climatic zones in Italy (from Zone A to Zone F), ensuring that energy assessmentsand retrofit recommendations are both accurate and contextually relevant to the building's geographical location. This climate sensitivity is essential to maintain the validity and applicability of the tool's outputs.  
The BEST tool has been developed in alignment with key European and national energy policies, particularly the objectives outlined in the European Green Deal, the Energy Performance of Buildings Directive (EPBD), and national long-term renovation strategies. The reference values for steady-state thermal transmittance were derived from the Italian Ministerial Decree of 6 August 2020, _\"Technical requirements for access to tax deductions for the energy retrofitting of buildings--so-called Ecolonus\"_ (Official Gazette No. 246, 5 October 2020), Annex E--Requirements for thermal insulation interventions, Table 1--Maximum allowable transmittance values for eligibility for tax incentives.  
The periodic transmittance values, attenuation factor, time shift, and internal areal heat capacity obtained through the application of various thermal insulation solutions were compared with the limit values set by the Ministerial Decree on Minimum Requirements (26 June 2015) and the UNI EN ISO 13786:2008 standard [40].