DesignBuilder EnergyPlus simulations can generate extensive data on environmental conditions within the building and resultant occupant comfort levels. The following comfort-related output is available:
The Discomfort hrs data above is equivalent to ASHRAE 'unmet load hours'.
The above data can be displayed at all time increments. In addition, air, radiant and operative temperatures can be displayed as distribution curves (below).
You can find more detailed information about Fanger, Pierce and Kansas State University Thermal comfort prediction algorithms in the EnergyPlus Background Section.
The Mech Vent + Nat Vent + Infiltration data is the sum of fresh air delivered through the HVAC system, infiltration and natural ventilation outside airflow in air changes per hour (ac/h). When used together with the other environmental output it can be very useful in checking for occupant discomfort.
Note 1: It is possible to display comfort data for occupied periods only by selecting 2-Just occupied periods as Zone environmental and comfort reports on the Output tab of the simulation options dialog. This option applies to all data described in this Comfort Analysis help section.
Note 2: Comfort data are not generated when the Gains data model option is set to Lumped. This is because in EnergyPlus the request for comfort calculations is made in the 'PEOPLE' statement and this is not used with Lumped gains.
The comfort data listed above is calculated for blocks using floor area weighted averages of the zones in the block. For example:
Block average Air temperature (Ta) = (A1 x Taz1 + A1 x Taz2 + A3 x Taz3 + ...) / (A1 + A2 + A3 + ...)
Where:
An is floor area of zone n,
Tazn is the air temperature of zone n
There is one exception, Mech Vent + Nat Vent + Infiltration, which is calculated in a similar way but using volume-weighted averages, i.e. using zone volumes instead of floor areas in the above equation.
Building data is calculated in the same way but including all blocks.
if the Include unoccupied zones in block and building totals and averages option is not set then unoccupied zones are not included in the above equation.
Note: if all zones in the block/building are unoccupied and the option is not set the denominator is zero and an error message is shown and results are deleted.
If you requested Temperature distribution data prior to the simulation, you can generate temperature distribution curves showing 'hours at', 'hours below' and 'hours above' temperature levels in 1°C temperature intervals during the occupied period. Bins include data for the labelled temperature through to that temperature + 1°C, so for example, the bin labelled '12°C' holds data for all temperatures in the range 12°C <= T < 13°C.
To view temperature distribution data set the Interval option in the Display Options panel to Distribution and the Data option to Comfort. This data can be useful for getting an overview of the levels of comfort (or otherwise) provided by the building over time. The results can be compared with benchmark comfort criteria.
For example, CIBSE provides recommended benchmark summertime peak temperatures and overheating criteria as follows:
Offices, schools, dwellings (living areas) should have no more than 1% of the annual occupied hours over operative temperature of 28°C. Bedrooms in dwellings should have no more than 1% of the annual occupied hours over operative temperature of 26°C.
UK DfES Building Bulletin BB87 recommends an allowable overheating criteria of 80 occupied hours in a year over and air temperature of 28°C.
Note 1: Temperature distribution data is only available at zone level.
Note 2: This data is not available when using Lumped gains model option as the data is tied in with the EnergyPlus 'People' data set and this is not generated for Lumped gains.
Note 3: This data is not available if the 1 time step per hour option is selected
Example Temperature Distribution Output
The Discomfort hours data is based on whether the humidity ratio and the operative temperature is within the region shown in ASHRAE Standard 55-2004 in Figure 5.2.1.1. For these outputs the operative temperature is simplified to be the average of the air temperature and the mean radiant temperature. For summer, the 0.5 Clo level is used and, for winter, the 1.0 Clo level is used. The graphs below are based on the following tables which extend the ASHRAE values to zero humidity ratio.
In some cases you may find a large number of discomfort hours for a particular zone even though the air temperature in the space is within normal ranges. If this happens you should check:
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You can also determine distributed comfort levels using CFD Comfort Calculations.