Location tab on model data at Site level
Location tab on model data at Site level
The Site precipitation data is used to describe the amount of precipitation on all Green roof surfaces over the course of the simulation. Precipitation includes both rain and the equivalent water content of snow. Precipitation is not yet described well enough in the usual building weather data file. So this object is used to provide the data using Schedule objects that define rates of precipitation in meters per hour. A set of schedules for site precipitation have been developed for USA weather locations and are provided with EnergyPlus in the data set called “PrecipitationSchedulesUSA.idf.” The user can develop schedules however they want. The schedules in the data set were developed using EnergyPlus’ weather file (EPW) observations and the average monthly precipitation for the closest weather site provided by NOAA. EPW files for the USA that were based on TMY or TMY2 include weather observations for Light/Moderate/Heavy rainfall, however most international locations do not include these observations. The values were modeled by taking the middle of the ranges quoted in the EPW data dictionary. The assumed piecewise function is shown below.
| Amount | Light | Medium | Heavy |
| m/h | 0.0125 | 0.052 | 0.1 |
The values were inserted on hour by hour basis for the month based on the observations. Then each month was rescaled to meet the average precipitation for the month based on the 30-year average (1971-2000) provided by the NOAA/NCDC. Therefore, the flags in the EPW file match the precipitation schedules for the USA. Note that summing the average monthly precipitation values will not give you the average yearly precipitation. The resulting value may be lower or higher than the average yearly value. Once the typical rainfall pattern and rates are scheduled, the Site Precipitation data provides a method of shifting the total rainfall up or down for design purposes. Wetter or drier conditions can be modelled by changing the Design Annual Precipitation although the timing of precipitation throughout the year will not be changed.
Magnitude of total precipitation for an annual period to be used in the model. Value selected by the user to correspond with the amount of precipitation expected or being assumed for design purposes. The units are in meters. This field works with the following two fields to allow easily shifting the amounts without having to generate new schedules. Units are m/yr or ft/yr
The schedule that describes the rate of precipitation. The precipitation rate schedule is analogous to weather file data. However, weather files for building simulation do not currently contain adequate data for such calculations. Therefore, EnergyPlus schedules are used to enter the pattern of precipitation events. The values in this schedule are the average rate of precipitation in meters per hour. The integration of these values over an annual schedule should equal the nominal annual precipitation.
Magnitude of annual precipitation associated with the rate schedule. This value is used to normalize the precipitation.
The Site Roof irrigation data is used to describe the amount of irrigation on all Green roof surfaces over the course of the simulation. You can define time-varying irrigation data using a maximum irrigation value and a schedule. There is also an option to apply some intelligence to the irrigation system to avoid over-watering the green roof.
Defines the way irrigation water is supplied. Select from:
Maximum rate of irrigation per hour. Units are m/h or ft/h.
The schedule defining the operation of the irrigation system. A schedule value of zero means the irrigation is switched off and a value of 1 means that the Max irrigation rate is used.