Design temperatures based on the standard
In the heating load calculation according to DIN/TS 12831-1, a design temperature of 20 °C is required for almost all rooms in which people regularly spend time. For rooms used without clothing, e.g. bathrooms and changing rooms, a temperature of 24 °C should be maintained. In commercially used rooms where standing activities are carried out, 17 °C is required for medium-heavy activities and 15 °C for heavy activities. In particular, the description of commercial spaces suggests that the design values have been derived using the comfort model. This becomes clearer when looking at DIN EN 16798-1. In the standard, the minimum design values for heating and the maximum values for cooling are specified depending on the category and the activity level. A clothing insulation of 1.0 clo is assumed for winter and 0.5 clo for summer (see Table 4). In order to check which comfort criteria are applied for the design temperatures, the temperatures for the limit values of the comfort categories are determined under the specified boundary conditions and compared with the standard values (see Table 5, the temperatures explicitly addressed in the following discussion are formatted in bold). The values from the comfort model coincide very well with the values for the summer period from DIN EN 16798-1. Only category II requires a design temperature of 26 °C, which is 0.4 K lower than the temperature at which 10 % of people are dissatisfied. The situation is different for the winter period: Here, the temperatures for sedentary activity differ by up to 0.9 K between the comfort model and the values from the standard. In the first two categories, the comfort model provides lower temperatures and turns for the other two categories. For the standing activity, on the other hand, the values for the first two categories again fit well. If you compare the values from the heat load calculation with DIN 16798-1, you can equate the requirements from the heat load calculation with those from category II. Compared to the comfort model, the values of the heat load calculation show a similar picture as in DIN EN 16798-1. Category II temperatures of the comfort model are about 1.0 K lower than required in the heat load calculation for the sedentary and standing activities with clothing. For the rooms that are used without clothing, however, the comfort model provides 25 °C for category II, which is 1.0 K higher than the 24 °C used in the heating load calculation.
Basically, it can be observed that the values from the standards are based on the comfort model. For individual values, however, the results from the model have been slightly adjusted for the standard. The reasons for the adjustments cannot be derived from the given information, especially since DIN EN 16798-1 specifies all input parameters for the comfort model.
Influence of design temperature on capacity and energy demand
From the values in Table 5, we can see the logical relationship that with more clothing, the temperature in the room can be lower in order to perceive the environment as comfortable. Now the question can be asked, what is an appropriate level of comfort provided by building technology, so as not to promote unnecessary energy consumption? For example, does it make sense with regard to energy expenditure to create a comfortable environment in winter for people in summer clothing? How many dissatisfied people can be accepted when calculating peak loads? In order to better estimate the influence of the design temperatures on the load calculation and the energy demand, the heat load according to DIN/TS 12831-1, the maximum heat load and the annual heating energy demand are determined below for two example buildings from an annual simulation of the module Dynamic Cooling Load in LINEAR Building for several design temperatures (see Figure 2).