## 4 Post-Retrofit vs. Pre-Retrofit Performance  
An overall post-evaluation of the energy retrofit projects that were carried out in the three public schools is presented. The technical impacts of implementing the retrofit projects will be evaluated, considering a one-year period of the schools' operation after the completion of the retrofits. Onsite monitored data is reported on a holistic level, mainly the schools' overall heating and electricity consumption. Therefore, overall district heating energy consumption data from heating meters are collected on the level of the whole school, while the overall school electricity consumption meter is also considered in the analysis. The energy performance monitoring post-retrofit period chosen in this investigation is a year spanning from October 2018 to September 2019. The energy consumption of the schools in this period will be compared with the energy consumption in the pre-retrofit period from October 2017 to September 2018. Figures 4-6 shows the monthly heating and electricity consumption of the three schools, when comparing the pre-retrofit data with the post-retrofit data. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**School A** & **School B** & **School C** \\ \hline Upgrading the lights in all the building blocks with energy efficient T5 and T8 tube LED lights. Insulating the interior layer of the attic space area of 7400 m\({}^{2}\) under the tilted roof in nine building blocks with 250 mm mineral wool. Insulating an area of 95 m\({}^{2}\) of exterior walls in one block with 190 mm of mineral wool insulation on the interior side. Upgrading single-glazed windows, glass doors in 7 blocks with double-glazeded energy efficient components (design U-value of 1.3 W/m\({}^{2}\)-K) with new frames. Upgrading skylights in 8 building blocks with energy efficient glazing of U-value around 1.4 W/m\({}^{2}\)-K. Replacing four domestic hot water circulation pumps. Upgrading the strategy for heating setpoint management in each of the building blocks. Insulating pipes, valves and pumps in all technical rooms. & Upgrading the lights in all the building blocks  
Figure 4: School A monthly (a) heating and (b) electricity pre-retrofit vs. post-retrofit data. Figure 5: School B monthly (a) heating and (b) electricity pre-retrofit vs. post-retrofit data. Figure 6: School C monthly (a) heating and (b) electricity pre-retrofit vs. post-retrofit data. Overall, the impact of implementing the energy retrofit projects is very different in the three schools, majorly regarding the effect on the heating and electricity consumption. While the data report an overall reduction in the electricity consumption for the majority of the months in the three schools, the case is different in terms of heating consumption. For example, the heating energy savings for the three schools range from 23% to 33% in February, and around 26% to 40% in March. Nevertheless, some months still exhibit higher energy consumption for the post-retrofit period when compared to the pre-retrofit period, as noted for the month of May. Table 3 summarizes the overall technical impacts of the three retrofit projects based on the actual data collected. It is reported that the three schools exhibit a reduction on the heating and electricity consumption profiles after one year of the retrofit project implementation. While Schools A and B have an overall annual heating savings of around 15%, School C registers only 9% reduction on the heating demand. On the other hand, School B exhibits the largest electricity savings of around 15%, when compared to 13% for School C and just over 2% for School A. While the building electricity and heating consumption are mainly governed by the systems and devices efficiency and operation, as well as the usage and management of the building, the heating consumption is largely affected by the ambient air temperature profile.