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--- planning:non-residential_passive_house_buildings:building_automation [2023/11/08 14:00] – [Frost protection of the heat exchanger] wolfgang.hasper@passiv.de
+++ planning:non-residential_passive_house_buildings:building_automation [2024/06/06 13:05] (current) – yaling.hsiao@passiv.de
@@ Line 10: / Line 10: @@
 For the operation of ordinary non-residential buildings, the automation of important functions is a necessity without which economic operation cannot be achieved. Energy efficient, optimised operation of the building can also be ensured if this is properly designed and executed. It also includes the possibility of data collection on a wide scale for systematic operations monitoring.
-Away from these ideal concepts, actual project experiences are often disillusioning. The functions in building automation are not always satisfactory and, especially in Passive House buildings, often aren't adapted to the requirements of energy-efficient operation. For example, there is almost a conflict with traditional approaches in the area of ventilation systems with heat recovery. The commonly used bypass control targeting a specified supply air temperature of e.g. 20 °C, regardless of the other boundary conditions in the building and time of year leads to unnecessary ventilation losses on mild winter days. Balanced operation and adherence to planned operating times are central to overall efficiency, but are not always successfully realised. Unintentional summer heating and increased system losses due to poorly adjusted flow temperatures have also been identified in many monitored projects.
+Away from these ideal concepts, actual project experiences are often disillusioning. The functions in building automation are not always satisfactory and, especially in Passive House buildings, often aren't adapted to the requirements of energy-efficient operation. For example, there is almost a conflict with traditional approaches in the area of ventilation systems with heat recovery. The commonly used bypass control targeting a specified supply air temperature of e.g. 20 °C, regardless of the other boundary conditions in the building and time of year leads to unnecessary ventilation losses on mild winter days and wastes a cooling potential in the summer. Balanced operation and adherence to planned operating times are central to overall efficiency, but are not always successfully realised. Unintentional summer heating and increased system losses due to poorly adjusted flow temperatures have also been identified in many monitored projects.
 A frequent point of disagreement with users as well as with the requirements for efficient operation is the control of shading systems when they are operated without regard to the season and individual preferences.
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 The frequently encountered parallel structure of partial automation systems of the various trade disciplines usually does not produce satisfactory results because the exchange of information between the subsystems is incomplete or even non-existent. For example, a shading system cannot react to the room temperatures or heating operation, or a ventilation system cannot reduce heat recovery at the right time in spring.
-In addition, commissioning is also made more difficult since several usually quite different systems have to be understood, operated and optimised. The availability of data for operations monitoring is accordingly just as limited and spread over several sources. Simply the collation of data alone is a challenge.
+In addition, commissioning is also made more difficult since several usually quite different systems have to be understood, operated and optimised. The availability of data for operations monitoring is accordingly just as limited and scattered across several sources. Simply the collation of data alone is a challenge.
 It is therefore expedient to set up a single, cross-discipline automation system. The thermal condition (more of which later) of the building can provide a useful parameter for the coordinated control and regulation of building functions.
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 In non-residential Passive House buildings, there is a favourable response with very little influence on energy consumption due to deviations. Extending the daily usage times has hardly any noticeable influence on the energy consumption. Nevertheless, setback periods outside of the times of use with back-up operation/standby mode at 17-18°C is effective to a smaller extent and can be useful given the typically long downtimes of non-residential buildings. The accordingly slightly higher heating load must then be taken into account; guidance on this is given in AkkP 51.
-Seasonally different control schemes of shading equipment is necessary in order to enable solar heat gains in the winter and to avoid overheating of rooms in the summer. A threshold value of approx. 150 W/m² (global radiation) on the façade plane is a reasonable guideline.
+Seasonally different control schemes of shading equipment is necessary in order to allow solar heat gain in the winter and to avoid overheating of rooms in the summer. A threshold value of approx. 150 W/m² (global radiation) on the façade plane is a reasonable guideline.
 Demand-based control of lighting installations can save significant amounts of electrical energy if these have a low auxiliary energy demand, including that for standby mode. This can support, but cannot be a substitute for, attentive building planning for a high degree of daylight autonomy and optimised specialist lighting planning.
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 A similar process should be followed in reversed order at the approach of autumn and winter.
-In efficient buildings, the customarily used outdoor temperature is not a suitable basis for estimating processes inside the building. A dynamic model-based approach which takes into account all influences of the weather (especially outdoor temperature and solar radiation) in addition to the usage-related heat gains etc. is very complex and too rigid for changes in use. However, the building itself continuously integrates all influences in the temperature of the deep building mass (concrete core temperature). This represents a suitable (low-pass) filter for the more strongly fluctuating room temperatures, and provides clear indications of the long-term development.
+In efficient buildings, the customarily used outdoor temperature is no longer a suitable basis for controlling the heating or estimating processes inside the building.
+A dynamic model-based approach which takes into account all influences of the weather (especially outdoor temperature and solar radiation) in addition to the usage-related heat gains etc. is very complex and too rigid for changes in use.
+However, the building itself continuously integrates all influences in the temperature of the deep building mass (concrete core temperature). This represents a suitable (low-pass) filter for the more strongly fluctuating room temperatures, and provides clear indications of the long-term development.
 This kind of control concept, based on directly measured concrete core temperatures, was successfully implemented in the FOS/BOS Erding school project and extensive monitoring was carried out with funding by the DBU (German Environment Foundation, Project Number 26170/02). The control concept proved to be very successful; the concrete core temperatures from a larger number of rooms were averaged and the thermal condition of the building was determined from the average temperature. By defining thresholds and hystereses, it was possible to switch automatically between heating, neutral and cooling mode:
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 |Cooling: night-time ventilation|≥ 23,5 (23,4)|
-Any short-term alterations in the operating status were excluded due to the inertia of the building's thermal mass. Conversely, it was possible to respond automatically to unusual weather or usage phenomena such as late cold spells or increased internal heat gains without problem.
+Any unwanted short-term alterations in the operating status were reliably avoided due to the inertia of the building's thermal mass. Conversely, it was possible to respond automatically to unusual weather or usage phenomena such as late cold spells or increased internal heat gains without problem.
 ==== Determining the thermal condition from measured room temperatures ====
-Determination of the thermal condition from direct measurement of the concrete core temperature has proved to work well, but this measurement is relatively laborious because it requires an additional number of sensors which must be set up, maintained, calibrated and evaluated. However, the thermal condition for a room can be calculated with sufficient accuracy on the basis of the prevailing room temperature using a simple thermal model of a concrete ceiling.
+Determination of the thermal condition from direct measurement of the concrete core temperature has proved to work well, but this measurement is relatively costly as it requires an additional number of sensors which must be set up, maintained, calibrated and evaluated. However, the thermal condition for a room can also be calculated with sufficient accuracy on the basis of the prevailing room temperature using a simple thermal model of a concrete ceiling.
 {{  :picopen:building_automation.png?700  }}
-In this way, the desired information can be provided easily and cost-effectively. Data from a number of suitable model rooms are averaged and smoothed over a period of 24 hours in order to obtain the thermal condition of the building. The systems can be controlled according to this. In contrast to the approach used for the FOS/BOS Erding, more refined threshold values are defined which could look like this for example:
+In this way, the desired information can be provided easily and cost-effectively, based on data from room sensors that are specified for general control purposes anyway. Data from a number of suitable model rooms are averaged and smoothed over a period of 24 hours in order to obtain the thermal condition of the building. The systems can be controlled according to this figure. Going beyond the approach used for the FOS/BOS Erding, more refined threshold values are defined which could look like this for example:
 ^Mode^24 h average building component temperature ϑThZ [°C] (hysteresis)|
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     D2 = 0.025
     D3 = 0.025
-    D4 = 0.05
+    D4 = 0.025
-    D5 = 0.05
+    D5 = 0.025
     # surface heat transfer coefficient, approx. 5.8 W/(m²K) radiative, convective disregarded as highly depending on direction of heat flow
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 # for control applications best use a 24 hour running mean of t5 / the thermal condition, in order to
-# smooth out the slight diurnal cyle (cycle)
+# smooth out the slight diurnal cyle
 </code>
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 The temperature level in heating systems should be adapted to the demand in order to avoid unnecessarily high heat losses in heat generators and distribution systems, to allow condensation of water vapour from combustion processes, and to increase the coefficient of performance of heat pump systems.
-In intermittently operated non-residential buildings, the heating system is switched to back-up mode at night and on weekends for maintaining a minimum temperature of 17 °C, for example. Effectively, the heating system is switched off for this purpose, since in a Passive House building cools down slowly and does not reach this level within just a weekend. Back-up operation usually only becomes effective on the third or fourth day of interruption of use, i.e. on long weekends or during vacation periods. Heating is then only necessary again for heating up before the start of operations. This intermittent use results in a diurnal dynamic with the highest heating output demand in the early morning, which declines as the day progresses and often reaches a marginal limit around noon. This effect is particularly pronounced in schools and other buildings used by many people, and results from the use-related heat generated by the presence of many people, artificial lighting and computers etc.
+In intermittently operated non-residential buildings, the heating system is switched to back-up mode at night and on weekends for maintaining a minimum temperature of 17 °C, for example. Effectively, the heating system is switched off for this purpose, since a Passive House building cools down only slowly and does not reach this level within just a normal weekend. Back-up operation usually only becomes effective on the third or fourth day of interruption of use, i.e. on long weekends or during vacation periods. Heating is then only necessary again for heating up before the start of operations. This intermittent use results in a diurnal dynamic with the highest heating output demand in the early morning, which declines as the day progresses and often reaches a marginal limit around noon. This effect is particularly pronounced in schools and other buildings used by many people, and results from the use-related heat generated by the presence of many people, artificial lighting and computers etc.
-For optimised operation of the heating system, exactly the required output should be available in each case, just matching the output requirement of the building. A minimised temperature of the medium in each case can significantly influence the coefficient of performance of a heat pump and also reduce fluegas losses in a condensing boiler. Due to the steep increase in Carnot efficiency at low temperature differences of the heat pump process, any improvement here tends to have a significant effect.
+For optimised operation of the heating system, exactly the required output should be available in each situation, just matching the output requirement of the building. A minimised temperature of the medium can significantly influence the coefficient of performance of a heat pump and also reduce fluegas losses in a condensing boiler. Due to the steep increase in Carnot efficiency at low temperature differences of the heat pump process, any improvement here tends to have a significant effect.
-In order to achieve a thermodynamic advantage at the heat generator, the forward flow temperature should not be controlled via return flow addition/mixing. Instead, the generator should always provide only the required temperature. Unless there is a particularly high demand for hot water, decentralised hot water generation with electric instantaneous water heaters is often a favourable solution in non-residential buildings. But even in centralised systems, the heat generator should provide high temperatures only for a short time for hot water generation.
+In order to achieve a thermodynamic advantage at the heat generator, the forward flow temperature should never be controlled via return flow addition/mixing. Instead, the generator should always provide only the required temperature. Unless there is a particularly high demand for hot water, decentralised hot water generation with electric instantaneous water heaters is often a favourable solution in non-residential buildings and avoids a driver for high temperature in the main heating system. But even in centralised systems, the heat generator should provide high temperatures only for a short time for hot water generation.
-The simple and generally established control of the heating medium temperature based on the outdoor temperature using a control curve is not suitable for Passive Houses since due to the high thermal time constant of the system and the large influence of free heat, only a very weak correlation of the heating output with the outdoor temperature remains. Since many heat generators do not have an alternative control option, in the past the only easy possibility here was often a characteristic curve that was as flat as possible and was sufficiently shifted in parallel to provide a quasi-constant flow temperature. Thus the possibilities of adapting to the demand remain unused, of course.
+The simple and generally established control of the heating medium temperature is based on the outdoor temperature using a control curve. It is not suitable for Passive Houses since due to the high thermal time constant of the building and the large influence of free heat, only a very weak correlation of the heating output with the outdoor temperature remains. Since many heat generators do not have an alternative control option, in the past the only easy possibility here was often a setting of the control curve that was as flat as possible and sufficiently shifted up in order to provide a quasi-constant flow temperature. Thus the possibilities of adapting to the demand remain unused, of course.
 {{  :picopen:building_automation_2.png?1000  }}
-In the illustration above, the flow temperature setpoint (red) is controlled quite conventionally according to a characteristic curve based on the mixed outdoor temperature. The correlation with the actually required heating output (orange, right axis) is often inconsistent. In some time periods, the forward flow temperature appears higher than necessary (e.g. regularly in the second half of the week), whereas in the heating-up phases after the interruption of operation at the weekend it is sometimes likely too low.
+In the illustration above, the flow temperature setpoint (red) is controlled quite conventionally according to a control curve based on the mixed outdoor temperature. The correlation with the actually required heating output (orange, right axis) is often inconsistent. In some time periods, the forward flow temperature appears higher than necessary (e.g. regularly in the second half of the week), whereas in the heating-up phases after the interruption of operation at the weekend it is sometimes likely too low.
-If the thermal condition of the building is known, it can be used as an input value for characteristic curve control of the temperature of the medium. This already leads to a much improved correlation with the actual output demand. In its simplicity, this characteristic curve method is certainly not optimal: short-term heat gains, especially from solar radiation, cannot be directly compensated. However, if the heating system is also switched off for the rest of the day when the pump speed falls below a minimum, i.e. when the flow rate is marginal, even this simple approach can work well.
+If the thermal condition of the building is known, it can be used as an input value for the control curve of the temperature of the medium. This already leads to a much improved correlation with the actual output demand. In its simplicity, this improved control curve method is certainly not optimal: short-term heat gains, especially from solar radiation, cannot be directly compensated. However, if the heating system is also switched off for the rest of the day when the pump speed falls below a minimum, i.e. when the flow rate is marginal, even this simple approach can work well.
 {{  :picopen:building_automtation_3.png?1000  }}
-The second figure shows an example of the flow temperature setpoint (red) determined according to a characteristic curve based on the thermal condition (grey). The required heating output is plotted at the bottom in orange, with reference to the Y-axis on the right. Compared to the outdoor temperature-related approach in the previous figure, a significantly improved correlation of the provided system temperature and required heating output can be seen. This already appears quite promising as long as the heating system is switched off during the weekends.
+The second figure shows an example of the flow temperature setpoint (red) determined according to a control curve based on the thermal condition (grey). The required heating output is plotted at the bottom in orange, with reference to the Y-axis on the right. Compared to the outdoor temperature-related approach in the previous figure, a significantly improved correlation of the provided system temperature and required heating output can be seen. This already appears quite promising as long as the heating system is switched off during the weekends.
-Real output-based control that always provides only the minimum forward flow temperature for supplying the critical room is ideal. It must be assessed in each individual case whether the additional effort compared to the characteristic curve method based on the thermal condition justifies the expense. Possibilities here include regulation according to the measured heating surface temperatures, valve positions of the thermostatic valves or the cooling rate of the heating water, which usually requires some additional effort for data logging. The upturn in electronic data collection and transmission offers far-reaching new possibilities here, which should, however, always be evaluated against the background of reliable functioning over decades.
+True output-based control that always provides only the minimum forward flow temperature for supplying the critical room is ideal. It must be assessed in each individual case whether the additional effort compared to the characteristic curve method based on the thermal condition justifies the expense. Possibilities here include regulation according to the measured heating surface temperatures, valve positions of the thermostatic valves or the cooling rate of the heating water, which usually requires some additional effort for data acquisition. The upturn in electronic data collection and transmission offers far-reaching new possibilities here, which should, however, always be evaluated against the background of reliable functioning over decades.
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-==== Regulation of the supply air temperature ====
+==== Control of the supply air temperature ====
 Conventional buildings or even existing buildings with a lower standard of insulation in which ventilation only takes place with cold outdoor air via windows are thermally 'unstable' and cool down to uncomfortable temperatures within a few hours as soon as the heating is switched off or breaks down.
-On the other hand, buildings are generally thermally 'inert' due to their large mass, i.e. heating-up processes, for example after window ventilation or after a night-time setback can therefore only be realised with time constants of a few hours, even in old buildings. For this reason, the room temperature must be maintained at a specified setpoint, e.g. 21°C, with the help of possibly complex control algorithms.
+On the other hand, buildings are generally thermally 'inert' due to their large mass, i.e. heating-up processes, for example after window ventilation or after a night-time setback can therefore only be realised with time constants of a few hours, even in old buildings. For this reason, the room temperature must be maintained at a specified setpoint, e.g. 21°C, with the help of possibly complex control algorithms. Overshooting of the temperature is particularly problematic for control algorithms: if the heating output is increased linearly (proportional controller) depending on the difference between the room temperature and the setpoint, then after reducing and switching off of the heat output, the room temperature will usually rise above the setpoint and 'overshoot'. Additional integral or differential control components may also only inadequately prevent overshooting. This problem is well known in control engineering and is described in detail in the relevant textbooks, so it will only be briefly mentioned here. In buildings and with regulation of the room temperature, another control task arises when additional disturbance variables with possibly shorter time constants have to be taken into account, for example when window ventilation or a ventilation system (without heat recovery or with poor heat recovery) brings cold air into the room. Frost protection of heating coils must also be realised internally via adequate control in ventilation units with air heaters. Such control tasks can be solved with nested control loops (cascade control). An example of cascade control: the room is heated via heating surfaces. In addition to controlling the room temperature depending on the extract air temperature, it is also possible to directly observe the disturbance variable supply air temperature from the ventilation system. The supply air temperature controller with a temperature sensor in the supply air duct can directly affect additional heating of the supply air and thus correct cooling down in the room faster than would be possible with the extract air room temperature controller, which would only control the heating surfaces when the extract air temperature had dropped accordingly.
-Overshooting of the temperature is particularly problematic for control algorithms: if the heating output is increased linearly (proportional controller) depending on the difference between the room temperature and the setpoint, then after reducing and switching off of the heat output, the room temperature will usually rise above the setpoint and 'overshoot'. Additional integral or differential control components may also only inadequately prevent overshooting. This problem is well known in control engineering and is described in detail in the relevant textbooks, so it will only be briefly mentioned here.
-In buildings and with regulation of the room temperature, another control task arises when additional disturbance variables with possibly shorter time constants have to be taken into account, for example when window ventilation or a ventilation system (without heat recovery or with poor heat recovery) brings cold air into the room. Frost protection of heating coils must also be realised internally via adequate control in ventilation units with air heaters.
-Such control tasks can be solved with nested control loops (cascade control). An example of cascade control: the room is heated via heating surfaces. In addition to controlling the room temperature depending on the extract air temperature, it is also possible to directly observe the disturbance variable supply air temperature from the ventilation system. The supply air temperature controller with a temperature sensor in the supply air duct can directly affect additional heating of the supply air and thus correct cooling down in the room faster than would be possible with the extract air room temperature controller, which would only control the heating surfaces when the extract air temperature had dropped accordingly.
-However, it turns out that these control concepts often deal with control tasks that are either not needed in Passive House buildings or even contradict the Passive House concept. In a Passive House building, ventilation with high-quality heat recovery ensures that the supply air is kept at a comfortable temperature ≥ 17°C all throughout. In addition, in Passive House buildings the internal heat sources (IHG) can contribute to heating of the rooms to an appreciable extent. Furthermore, the room temperature within the range of 20 to 25°C is defined as comfortable. This means that if the room temperature is within this range, neither heating nor cooling is required. It is well known from monitored projects that many users find a temperature of 22°C to be optimal.
+However, it turns out that these control concepts often deal with control tasks that are either not needed in Passive House buildings or even contradict the Passive House concept. In a Passive House building, ventilation with high-quality heat recovery ensures that the supply air is kept at a comfortable temperature ≥ 17°C all throughout. In addition, in Passive House buildings the internal heat sources (IHG) can contribute to heating of the rooms to an appreciable extent. Furthermore, the room temperature within the range of 20 to 25°C is considered as comfortable. This means that if the room temperature is within this range, neither heating nor cooling is required. It is well known from monitored projects that many users find a temperature of 22°C to be optimal.
-Assuming this, the above example shows that a simple control system for supply air post-heating, which keeps the supply air temperature at a constant T<sub>Zuluft</sub> = 21°C  is not suitable for a Passive House building:
+Assuming this, the above example shows that a simple control system for supply air post-heating, which keeps the supply air temperature at a constant T<sub>SUP</sub> = 21°C is not suitable for a Passive House building: With the thermally well-insulated building envelope and especially airtightness and the heat recovery ventilation system for the Passive House building, building characteristics exist which basically keep the room temperature and thus thermal comfort in indoor spaces at a constant level. The thermal inertia of the building is so great that short-term, spatially limited temperature fluctuations, e.g. due to a rare open window are quickly buffered away. If there are radiators the supply air in the Passive House building does not need to be heated any further apart from the frost protection pre-heating described above. The minimal supply air temperature of 17°C is sufficient and in this way good use can be made of the temporary IHG and solar heat gains ('free heat'). However, if the supply air is always (expensively) kept at 21°C, this often leads to undesirable overheating of the rooms, which the users may ventilate away via windows unless the heat recovery is already automatically regulated in the unit. In both cases, however, the use of free heat is prevented and the Passive House concept is counteracted.
-With the thermally well-insulated building envelope and especially airtightness and the heat recovery ventilation system for the Passive House building, building hardware exists which basically keeps the room temperature and thus thermal comfort in indoor spaces at a constant level. The thermal inertia of the building is so great that short-term, spatially limited temperature fluctuations, e.g. due to a rare open window are quickly buffered away.
-If there is a surface heating system, then the supply air in the Passive House building does not need to be heated any further apart from the frost protection pre-heating described above. The minimal supply air temperature of 17°C is sufficient and in this way good use can be made of the temporary IHG and solar heat gains ('free heat'). However, if the supply air is always (expensively) kept at 21°C, this often leads to undesirable overheating of the rooms, which the users may ventilate away via windows unless the heat recovery is already automatically regulated in the unit. In both cases, however, the use of free heat is prevented and the Passive House concept is counteracted.
-The control task must therefore be defined differently and is even much easier in a Passive House building: the comfortable range is T<sub>Room</sub> = 20 to 25°C or possibly 22 to 25°C if desired by the users, e.g. in nursing homes. A (temporary) increase in the room temperature within this range due to free heat can be acceptable and is usually even desired. This is because heat gains during the day can and should be deliberately stored in the building mass. Over-sensitive regulation is not only costly, but is usually also counterproductive: thus (in winter) the bypass function of the heat recovery system must not be activated under any circumstances in order to keep  T<sub>Supply air</sub> at 21°C, and cooling must not be used at all.
+The control task must therefore be defined differently and is even much easier in a Passive House building: the comfortable range is T<sub>Room</sub> = 20 to 25°C or possibly 22 to 25°C if desired by the users, e.g. in nursing homes. A (temporary) increase in the room temperature within this range due to free heat can be acceptable and is usually even desired. This is because heat gains during the day can and should be deliberately stored in the building mass. Over-sensitive regulation is not only costly, but is usually also counterproductive: thus (in winter) the bypass function of the heat recovery system must not be activated under any circumstances in order to keep T<sub>Supply air</sub> at 21°C, and cooling must not be used at all. Instead of a fixed value for the supply air temperature, the room temperature should therefore be observed as a control variable in the Passive House building. In non-residential buildings, the extract air temperature or a suitable average value obtained from both can also be used. Of course, very high IHG must be considered and controlled separately for zones with special uses. The thermal condition of the building may provide information as to whether gains from free heat are desirable or should be avoided at a given time. If this is not available, T<sub>outdoor air</sub> < 16°C (comfort criterion) for more than 7 hours per day may serve as an alternative criterion for winter operation with full heat recovery. If a purely calendar based solution is to be implemented (which cannot respond to unusual weather conditions, but is usually correct), a decision can be made based on the monthly mean values of the outdoor air temperature [AkkP 44]. A similar approach is also conceivable based on measured weather data using a moving monthly average.
-Instead of a fixed value for the supply air temperature, the room temperature should therefore be observed as a control variable in the Passive House building. In non-residential buildings, the extract air temperature or a suitable average value obtained from both can also be used. Of course, very high IHG must be considered and controlled separately for zones with special uses. The thermal condition of the building may provide information as to whether gains from free heat are desirable or should be avoided at a given time. If this is not available, T<sub>outdoor air</sub> < 16°C (comfort criterion) for more than 7 hours per day may serve as an alternative criterion for winter operation with full operation of heat recovery. If a purely calendar based solution is to be implemented (which cannot respond to unusual weather conditions, but is usually correct), a decision can be made based on the monthly mean values of the outdoor air temperature [AkkP 44]. A similar approach is also conceivable based on measured weather data using a moving monthly average.
+It is important to note that the 'winter' period defined above is significantly longer than the heating period in a Passive House building. This is because in the transitional period (around April to May and September to October) with moderate outdoor temperatures, ventilation with HR is important to ensure comfortable supply air temperatures. On the other hand, it may also make sense to activate bypass operation on individual days and hours with T<sub>ODA</sub> > 25°C. Measurement of the temperatures in the fresh air, extract air and exhaust air ducts and a corresponding control mechanism with the control unit of the ventilation unit can be used for this purpose. Again, transparency relating to the algorithm used is important for commissioning and optimisation of operation.
-It is important to note that the 'winter' period defined above is significantly longer than the heating period in a Passive House building. This is because in the transitional period (around April to May and September to October) with moderate outdoor temperatures, ventilation with HR is important to ensure comfortable supply air temperatures. On the other hand, it may also make sense to activate bypass operation on individual days and hours with T<sub>outdoor air</sub> 25°C. Measurement of the temperatures in the fresh air, extract air and exhaust air ducts and a corresponding control mechanism with the control unit of the ventilation unit can be used for this purpose. Again, transparency relating to the algorithm used is important for commissioning and optimisation of operation.
 ===== Shading =====
-Movable shading elements are particularly conspicuous to building users and their (often noisy) movement is often perceived as annoying. In addition, individual preferences of different users must be balanced with operation of the shading adjusted to the season. Well-designed control and regulation is therefore of particular importance for user acceptance and building function.
+Movable shading elements are particularly conspicuous to building users and their (noisy) movement is often perceived as annoying. In addition, individual preferences of different users must be balanced with operation of the shading appropriate to the season. Well-designed control and regulation is therefore of particular importance for user acceptance and building function alike.
+Depending on the [[https://passipedia.org/planning/non-residential_passive_house_buildings/building_automation#concepts_for_automation_in_non-residential_passive_house_buildings|thermal condition]] of the building, solar heat gains are either desirable or to be avoided. Seasonal differentiation (determination of the seasonal operating mode) is therefore absolutely necessary. If solar gains are desired, the movable shading device will normally remain open. However, a possibility for user intervention is urgently required for the reasons mentioned above in order to take into account different preferences or requirements. It has proven effective to allow such user interventions for a limited time and then revert to the automatic signal again. A period of 2-3 hours avoids excessive patronising of users, but also ensures proper building operation.
-Depending on the thermal condition of the building, solar heat gains are either desirable or to be avoided. Seasonal differentiation (determination of the seasonal operating mode) is therefore absolutely necessary. If solar gains are desired, the shading will always remain open. However, a possibility for user intervention is urgently required for the reasons mentioned above in order to take into account different preferences or requirements. It has proven effective to allow such user interventions for a limited time at a time and then to use the automatic signal again. A period of 2-3 hours avoids excessive domination by users, but also ensures proper building operation.
+If solar gains are to be avoided, the shading device is normally closed when a threshold value for irradiation of approx. 150 W/m² (global radiation, ~ 15 kLux) is exceeded on the plane of the façade in question. On the other hand, user intervention is again possible at any time for a limited period of time.
-If solar gains are to be avoided, the shading device is automatically closed when a threshold value for irradiation of approx. 150 W/m² (global radiation, ~ 15 kLux) is exceeded on the façade in question. On the other hand, user intervention is possible at any time for a limited period of time. If automatic operation is deployed again at fixed times then 06:00, 09:00, 12:00 etc. may constitute a reasonable framework.
+If automatic operation is deployed again at fixed times then a schedule of 06:00, 09:00, 12:00 etc. may constitute a reasonable framework.
-It always makes sense to have separate control of the shading devices at least with regard to the storey and orientation. If there is shading of the façades from neighbouring buildings, a critical elevation angle can also be included.
+It always makes sense to split control of the shading devices at least with regard to the storey and orientation. If there is shading of the façades from neighbouring buildings, a critical elevation angle can also be included. Solar position algorithms used in shading controls supply the actual value.
 The selection of a shading system that provides sufficient daylight is an additional planning aspect.
-Regulation should be based on measured values from a high-quality sensor that is calibrated in an appropriate manner. Only then can reliable functioning be expected in the long term. A global radiation sensor (horizontal) is appropriate in case of operations monitoring, the measured values can then also be processed into monthly values for irradiation at that location.
+Regulation should be based on measured values from a high-quality sensor that is calibrated in an appropriate manner. Only then can reliable functioning be expected in the long term. A global radiation sensor (horizontal) is appropriate in case of operations monitoring, the measured values can then also be processed into monthly values for irradiation at that site.
 ===== Sustainable operation =====
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 In the current discussions about the growing importance of building automation, the auxiliary energy demand required for the operation of these systems is rarely mentioned. In this respect a simple measurement of example components shows that a considerable amount of energy is used here.
-A large number of actuators, sensors and automation stations use electrical energy to perform the desired function. The respective power requirements appear to be low at first, many values are just a few watts. However, over the large number of elements the auxiliary energy demand adds up to a considerable amount.
+A large number of actuators, sensors and automation controllers (PLC) use electrical energy to perform the desired function. The respective power requirements appear to be low at first, many values are just a few watts. However, over the large number of elements the auxiliary energy demand adds up to a considerable amount. This effect can also be proved time and again through field measurements and appears as a substantial contribution to the standby power consumption of the building remaining outside the times of use. In a sample of larger non-residential Passive House buildings in Germany, more than 12 kWh/(m²a) was expended for the area in question. This value corresponds roughly to the useful energy consumption for heating energy or half of the use-related electricity consumption in an administrative building. This is therefore an area that must be taken very seriously, and a reduction in the auxiliary energy demand of automation systems seems to be urgently needed.
-This effect can also be proved time and again through field measurements and appears as a substantial contribution to the standby power consumption of the building remaining outside the times of use. In a sample of larger non-residential Passive House buildings in Germany, more than 12 kWh/(m²a) was expended for the area in question. This value corresponds roughly to the useful energy consumption for heating energy or half of the use-related electricity consumption in an administrative building.
-This is therefore an area that must be taken very seriously, and a reduction in the auxiliary energy demand of automation systems seems to be urgently needed.
-Since non-residential buildings are usually operated intermittently, large parts of the automation system can in principle also be switched off during the downtime. This would already result in considerable potential savings.
+Since non-residential buildings are usually operated intermittently, large parts of the automation system can, in principle, also be switched off during the downtime. This would already result in considerable savings.
 Furthermore, a fundamental improvement in the energy efficiency of the building automation components used would also be strongly desirable. The selection of more efficient power supply units that are better adapted to the consumers already holds great potential. The installation of a separate low-voltage network (24 V) in combination with high-quality, well-utilised power supply units is also a helpful approach. The preliminary work on energy labelling carried out within the framework of the Ecodesign process at the EU level has not yet been completed (2023). It remains to be seen whether ambitious specifications can be implemented here. The specifications must be based on a budgeted approach depending on the respective range of functions of a device.
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 |<del> <font inherit/inherit;;inherit;;#ffffff>D</font>  </del> |<del> <font inherit/inherit;;inherit;;#ffffff>1</font>  </del> |
-The measurement of a parameter, calculation of a control loop and output of the control signal, switching of a consumer and digital communication with a network or management and operation level (MOL) can be taken into account here. An evaluation methodology with an emphasis on efficiency that is realistic and easy to use should be developed for this purpose.
+The measurement of a parameter, calculation of a control loop and output of the control signal, switching of a consumer and digital communication with a network or management system (BMS) can be taken into account here. An evaluation methodology with an emphasis on efficiency that is realistic and easy to use should be developed for this purpose.
+The development of smartphones has proved that high processing capacity can be made available when required and that outside these times, extremely energy-efficient operation with battery supply is still possible. The relevant technologies are therefore available and would only have to be adapted for automation stations. For communication in a complex (IP) network and remote configuration of automation stations, significant processing power may be necessary temporarily, while the computation of common control loops has minimal requirements. The periodic collection of measured values is even less demanding.
+==== Switching on electrical loads ====
-The development of smartphones has proved that high processing capacity can be made available when required and that outside these times, extremely energy-efficient operation with battery supply is still possible. The relevant technologies are therefore available and would only have to be adapted for automation stations. For communication in a complex (IP) network and remote configuration of automation stations, significant processing power may be necessary temporarily, while the computation of common control loops has minimal requirements. The periodic collection of measured values is even less demanding.
+Relays for direct or indirect switching of loads play an important role in the use of electrical energy in automation stations. A continuous flow of current in the magnetic coil (equating to ~0.2…1 W) is necessary for switching on of the operating contact. Since many loads in buildings remain switched on over longer periods of time (e.g. pumps), a significant amount of energy is used here and unwanted heat may also be produced. In contrast, the usual relays are low-cost, reliable and revert into a defined state in case of a power failure. Improved efficiency when using conventional relays is easily possible by lowering the coil current after switching on – simply stopping the magnet keeper/ armature does not require the full current. This can be done flexibly by operating with pulse width modulation (PWM) or even by simply wiring with a serial resistor and a parallel capacitor, which can already save more than 60% of the energy consumption for the relays. The somewhat reduced vibration tolerance is of little relevance for applications in buildings. Another option is to use bistable relays, which are switched by current pulses but then maintain the switched state without current. They are more expensive than the usual, monostable relays, but consistently reduce energy consumption to a minimal amount.
-==== Switching on electrical consumers/loads ====
+Electronic relays (solid state relays) can be switched almost without power and have no moving parts. They also revert to a defined state in the event of a power failure and can change their switching state several times within a second. Even so, they are less interesting for building automation because they have a power loss of a few percent of the load. They therefore convert a considerable part of the switched current into heat and accordingly require a heat sink. Upcoming generations of semiconductors based on silicon carbide are expected to significantly reduce these losses. For long-term switched loads, however, the fundamental advantages of mechanically switched relays remain in place for the time being.
-Relays for direct or indirect switching of loads play an important role in the use of electrical energy in automation stations. A continuous flow of current in the magnetic coil (equating to ~0.2…1 W) is necessary for switching on of the operating contact. Since many loads in buildings remain switched on over longer periods of time (e.g. pumps), a significant amount of energy is used here and unwanted heat may also be produced. In contrast, the usual relays are low-cost, reliable and revert into a defined state in case of a power failure.
-Improved efficiency when using conventional relays is easily possible by lowering the coil current after switching on – simply stopping the magnet keeper/ armature does not require the full current. This can be done flexibly by operating with pulse width modulation (PWM) or even by simply wiring with a serial resistor and a parallel capacitor, which can already save more than 60% of the energy consumption for the relays. The somewhat reduced vibration tolerance is of little relevance for applications in buildings.
-Another option is to use bistable relays, which are switched by current pulses but then maintain the switched state without current. They are more expensive than the usual, monostable relays, but consistently reduce energy consumption to a minimal amount.
-Electronic relays (solid state relays) can be switched to almost without power and have no moving parts. They also revert to a defined state in the event of a power failure and can change their switching state several times within a second. Even so, they are less interesting for building automation because they have a power loss of a few percent of the load. They therefore convert a considerable part of the switched current into heat and accordingly require a heat sink. Upcoming generations of semiconductors based on silicon carbide are expected to significantly reduce these losses. For long-term switched loads, however, the fundamental advantages of mechanically switched relays remain in place for the time being.
 ==== Actuators ====
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 Interconnectivity of building automation components is an essential prerequisite for functioning as a system. The amount of energy used for operation of the connected components (storey distributors/switches etc.) is considerable. Both the investment costs as well as the operating costs for the systems are significant, even though building automation systems have low bandwidth requirements for the most part. It therefore makes sense to integrate the building automation into the physical IP network infrastructure which is already necessary in any case in order to achieve a high level of utilisation of the system instead of having to operate two systems in parallel.
-==== Heat generation ====
+==== Waste heat ====
 Secondary effects also arise with improved efficiency of the building automation components. The lower operating costs with the reduced power consumption are obvious, but planning and execution can also become easier with lower heat loads. Switch cabinets do not have to be ventilated or even cooled, and a more compact design becomes possible. The service life of electronic components is also extended as the surrounding temperature falls.
 The guiding principle for new development could be: "Every circuit should be designed as if it were powered by batteries, and one should learn from mobile devices".
 ==== Measurement uncertainty ====
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 For precise determination of the thermal condition, if it is to be applied for individual rooms or smaller room groups, and for checking the actual energy consumption, a measurement uncertainty of ≤ ± 0.3 K is required for the entire measurement chain in the temperature measurement. The class VDI/VDE 3512 A-TGA (based on a resistance thermometer Class A or AA according to EN 60751) should thus form the standard design, and for special cases an improved class "AA-TGA" (Class AA EN 60751 and improved measurement electronics for only half the measurement uncertainty) should be offered in an easily accessible form (for example for special control tasks in concrete core temperature control).
-High-quality electrodes exhibit low drift with changing ambient temperatures and over the course of time. Nevertheless, all measuring circuits change their characteristics, which is why a ratiometric measurement is to be preferred. A reference resistor is available for this, which can be regarded as almost invariable if the quality is appropriate. The measurement of the platinum temperature detector (RTD) is then always carried out in direct comparison to the reference resistor, all variations in the excitation current or the reference voltage at the AD converter are thus compensated. Measuring bridges for precise monitoring of temperature differences with two platinum measuring resistors can also be a helpful addition to the building automation repertoire.
+High-quality sensors exhibit low drift with changing ambient temperatures and over the course of time. Nevertheless, all measuring circuits change their characteristics, which is why a ratiometric measurement is to be preferred. A reference resistor is available for this, which can be regarded as almost invariable if the quality is appropriate. The measurement of the platinum resistance temperature detector (RTD) is then always carried out in direct comparison to the reference resistor, all variations in the excitation current or the reference voltage at the AD converter are thus compensated. Measuring bridges for precise monitoring of temperature differences with two platinum measuring resistors can also be a helpful addition to the building automation repertoire.
 Even with a high quality of implementation, at least a random check of the measurement uncertainty should be carried out at regular intervals. For this purpose, the organisational prerequisites must be created during planning and execution, such as clarification of responsibility and a budget. For all measured variables within a building automation system, it should be possible to store and edit at least the factor and summand for calibration in a simple and comprehensible manner.
-The same applies for sensors for relative humidity (typical measurement uncertainty ± 2  to 3 %). Particularly high reliability of the measurement usually isn't necessary in Central Europe; nevertheless, excessive deviation should be detected and corrected in time. An aspiration psychrometer or a dew point mirror provide a reasonably reliable reference for this.
+The same applies for sensors for relative humidity (typical measurement uncertainty ± 2 to 3 %). Particularly high reliability of the measurement usually isn't necessary in Central Europe; nevertheless, excessive deviation should be detected and corrected in time. An aspiration psychrometer or a dew point mirror provide a reasonably reliable reference for this. Special care should be taken if CO<sub>2</sub> sensors are used. Inexpensive sensors, such as those used for building automation, always exhibit a considerable drift due to their design. Regular calibration is therefore absolutely necessary in order to maintain the already comparatively large measurement uncertainty of around ±70 ppm and to avoid even greater deviations. If the sensor does not include suitable equipment for automatically carrying out such corrections, it should not be used, since annual recalibration is hardly feasible and very cost-intensive.
-Special care should be taken if CO2 sensors are used. Inexpensive sensors, such as those used for building automation, always exhibit a considerable drift due to their design. Regular calibration is therefore absolutely necessary in order to maintain the already comparatively large measurement uncertainty of around ±70 ppm and to avoid even greater deviations. If the sensor does not include suitable equipment for automatically carrying out such corrections, it should not be used, since annual recalibration is hardly feasible and very cost-intensive.
-Modern CO2 sensors include a mechanism for self-calibration based on the minimum value within a 10-14 day measurement period. By implication this assumes that within such a period the outdoor air concentration occurs due to abundant ventilation without occupants in the room. For common non-residential Passive House buildings with intermittent operation of the ventilation system, this state should occur during the pre-purge phase at the beginning of each day of operations. This mechanism can therefore reliably take effect here, unlike in residential buildings for example, where there is strong dependence on the habits of the respective occupants.
+Modern CO<sub>2</sub> sensors include a mechanism for self-calibration based on the minimum value within a 10-14 day measurement period. By implication this assumes that within such a period the outdoor air concentration occurs due to abundant ventilation without occupants in the room. For common non-residential Passive House buildings with intermittent operation of the ventilation system, this state should occur during the pre-purge phase at the beginning of each day of operations. This mechanism can therefore reliably take effect here, unlike in residential buildings for example, where there is strong dependence on the habits of the respective occupants.
 Irradiation sensors play a special role in Passive House buildings. At present, brightness sensors based on very inexpensive photodiodes are used to control shading systems. A separate diode is provided for each cardinal direction, protected by a simple plastic housing. This technical standard is insufficient and is not reliable over longer periods of time. All individual diodes have slightly different characteristics due to production and also age differently. In addition, the plastic cover becomes cloudy over time, which also causes a permanent change in the characteristics, apart from accumulation of dirt.
-Reliable operation of the shading system cannot be assured on such a basis, and control parameters once set must be adjusted later to compensate for aging/clouding of the sensors. It is also not possible to obtain reliable radiation readings for operational analysis as desired for energy-efficient buildings.
+Reliable operation of the shading system cannot be assured on such a basis, and control parameters once set must be adjusted later to compensate for aging/clouding of the sensors. It is also not possible to obtain reliable radiation readings for operational analysis as desired for energy-efficient buildings. It therefore appears expedient to strive for higher standards of radiation measurement in the future. Calibrated and temperature-compensated PV reference cells with glass covers in combination with a high-quality measuring circuit have the potential to be a low-cost alternative. With such sensors, horizontal global radiation of a sufficient quality is then available for control of shading and operational analysis. From the measured value, the irradiation on randomly oriented surfaces (e.g. façades) can be determined with the aid of a sky model and used as an input value for regulation.
-It therefore appears expedient to strive for higher standards of radiation measurement in the future. Calibrated and temperature-compensated PV reference cells with glass covers in combination with a high-quality measuring circuit have the potential to be a low-cost alternative.
-With such sensors, horizontal global radiation of a sufficient quality is then available for control of shading and operational analysis. From the measured value, the irradiation on randomly oriented surfaces (e.g. façades) can be determined with the aid of a sky model and used as an input value for regulation.
 ==== Durability of the automation system ====
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 ===== See also =====
+[[phi_publications:nr.59_building_automation_for_energy-efficient_buildings|Building automation for energy-efficient buildings]]
 More detailed information can be found [[https://database.passivehouse.com/de/download/product_page/Protokollband59|Protokollband 59 ]] (German)