Figure 1
The diagram shows a horizontal timeline from year 0 (the year the house was constructed) to year 50 of the house’s service life. Four indicative retrofit cycles span the 50-year period at years 5, 15, 25, and 35, labelled Cycle 1, Cycle 2, Cycle 3, and Cycle 4. Above the cycles, arrows labelled T1, T2, T3, and T4 indicate the time intervals associated with each cycle. Within each cycle, groups of vertical blue lines labelled S1, S2, S3, and S4 represent retrofit steps, while R1, R2, R3, and R4 represent retrofit packages (sets of retrofit measures) implemented at each step. The labels t1, t2, t3, and t4, placed between the vertical blue lines, represent indicative time intervals between retrofit steps. Each cycle includes a bracket labelled “Stepwise Retrofitting” below the blue lines to indicate that the cycle is completed through stepwise retrofitting. A double-sided arrow labeled Ts appears near the left side of the timeline between years 0 and 5, indicating a shorter time span: the time period that does not require any retrofitting.An indicative stepwise retrofitting process for 50 years. Note: Start time for retrofit cycles (Ts); Timing between retrofitting cycles (T1 – T4); Retrofit steps (Blue unbroken lines from S1 to S4); Intervals between retrofit steps (t1 – t4); Retrofit packages (R1 – R4). Source: Developed by authors