Modelling stages and analysis procedure

After the characteristics of the prototypes are introduced, the modelling stage in the simulation program takes place. However, before the explanations on how the modelling stages were conducted and how the results were analysed, it is important to acknowledge that:

o All the simulation results are produced in office hours, when the building is occupied, hence making the outputs more meaningful.

o The weather file used in this thesis provides the hourly weather data of Tehran.

o In Design Builder and in natural ventilation mode, the airflows are calculated from wind and stack pressures when carrying out simulation.

o The building context for which the simulation of the prototypes takes place is in an urban area.

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The prototypes generated and used in the software which undergo the simulation procedure are shown in Figure 7. 8. The prototypes themselves differ in terms of plan shape, orientation, atria type, and placement (unfix parameter). Below explains the number of different prototypes in more detail:

The porotypes cover the five selected atria types; central, 1-sided, 2-sided, 3-sided and linear. Building plan shapes are either square or rectangular as the reviewed literature identified that they are the most commonly used shapes in Tehran as well as ,statistically, the most commonly used plan shapes in the tallest buildings of the world. Therefore, two plan shapes for each of the five atria types totals ten prototypes, excluding the base case. The base case represents the typical office building blocks in Tehran, which do not have atrium (Figure 7. 6 and Figure 7. 7).

Moreover, each of these prototypes is examined with an orientation towards all four main compass directions (Figure 7. 8). Thus, for the 1-sided atria example, it is orientated towards the four directions producing four different scenarios. However, some atria types (such as central in a square shape) only have one option and orientation and do not produce a new scenario. Thus, the 10 prototypes provide 35 scenarios of different orientations. In addition, orientation is also considered in base building case with no atria ( in both square and rectangular plan shapes) which means the number of prototypes undergoing simulation stages is 38 (Figure 7. 8).

In order to simply refer to a certain prototype, the researcher has given coded names to each 38 prototypes that has been designed in order to undergo simulation. These names also indicate what the prototype looks like (Figure 7. 8). The first part of the name is the type of atria for the office building, namely 1-sided, 2-sided, 3-sided, central and linear. The second part indicates where the atrium is situated. Thus, if the atrium is on the north of an office building and has a 1-sided atria, the name of the prototype is 1-sided-N. If the building has a linear atrium which has external atria façades towards the east and west, the building is called a linear-EW model. The third part of the name is used in the rectangular category and gives a sense of how the building is orientated. For example, if a building with an atrium located on the NE (2 sided-NE) is aligned horizontally on the east-west axis, then that prototype is called 2- sided (H)-NE model. Figure 7. 8 shows all the full names of all prototypes with their plan shape.

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As for the number of simulations, the simulation stage has four categories depending on the season and control mode (Figure 7. 9). In section 6.3.3 and as illustrated in Figure 6.5 the detail of the evaluation stage has been explained. There are two seasons; cool season (which covers October to March) and warm season (which covers April to September). Having two separate simulations rather than one annual simulation is important because some input data or operational schedules are different for each season. Thus the simulation could not be completed in one attempt. Also, in each season there are two different control modes; NV mode only and HVAC+NV mode which uses HVAC when NV is not enough to provide a thermal comfortable temperature. Therefore, each of these 38 models undergoes four set of simulations stages: ‘warm season NV mode’, ‘cool season NV mode’, ‘warm season HVAC+NV mode’, and ‘cool season HVAC+NV mode’. Therefore, 38 prototypes multiplied by four equals 152 simulations. As explained all simulation results are outputs for office hours only, when the building is occupied, and situated in an urban area replicating Tehran city. Each simulation performance takes one day to be completed with the computer facilities available to the researcher at the time of the research. Also in order to produce reliable results a considerable amount of simulation has been conducted to understand how the software works and to generate correct results.

Figure 7. 9: Simulation Category

When the simulations are complete, there will be a comparative analysis of the various results that aims to identify the design characteristics that provides the least energy consumption in heating and cooling the office spaces, and provides most thermal comfort via natural means. The results of the prototypes with atria are also compared to the base case building with no

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atrium in the same simulation category. In other words, the base case acts as a benchmark and any prototype with more acceptable results than the benchmark could represent a potential design to consider in terms of lowering energy consumption for thermal comfort. Thus, the base case is a benchmark for assessing the designs with a more potential for lower energy consumption than the typical office buildings in Tehran.