Domestic Hot Water (DHW)

Activity tab in model data


DHW Consumption rate

In DesignBuilder the amount of DHW consumed is considered to be a function of the activity in the zone. For example, there is a demand assumed to arise from the occupants of an office for activities such as washing hands and washing up cups. This demand is associated with the office rather than the toilet or tea room. Thus the demand from each space needs to be assigned to a DHW system even if the system itself is not present in the space.


The effect of hot water consumption (hot water taps, showers etc) on building energy use can be included in your thermal model by switching on DHW on the HVAC tab.


The data on this tab defines the hot water consumption rate in each zone as l/day/m2 data (gal/day/ft in IP units). The DHW consumption data is only used if DHW is selected on the HVAC tab.


The DHW consumption rate is the amount of water used over a whole day per floor area. The consumption should be entered for the day of the year having the most consumption. For example in an office it might the consumption over a typical work day. You should not enter an average rate over the year including reduced rates on weekends etc.


Note: If you have DHW consumption data in l/person/day format you can convert to the l/m2-day format used in DesignBuilder by multiplying it by occupant density (people/m2).


With Simple HVAC, the hot water generation system is defined under DHW on the HVAC tab.


Note: This DHW consumption data is also used in Detailed HVAC with the default 1-Simple HVAC Detailed HVAC Activity data setting.