Simulation Detailed Results
The main Display options
are in the bottom left of the screen. They allow you to control the content
of the Detailed data and also the Display style.
The 'Analysis' tab has detailed simulation results (displayed as a line
graph by default).
See also the Analysing Simulation Results Tutorial
For more on how the output is calculated see: Calculation
of DesignBuilder Output from EnergyPlus Report Variables.
Environmental/Comfort Output
- Air Temperature
- the calculated average temperature of the zone air.
- Radiant Temperature
- the (area * emissivity) weighted average of the zone inside surface temperatures.
- Operative Temperature
- the mean of the zone air and radiant temperatures.
- Outside Dry-Bulb Temperature.
- Relative Humidity
- the calculated average relative humidity of the air.
- Fanger PMV - Fanger
Predicted Mean Vote calculated according to ISO 7730.
- Pierce PMV ET -
the Predicted Mean Vote (PMV) calculated using the effective temperature
and the Pierce two-node thermal comfort model.
- Pierce PMV SET -
the Predicted Mean Vote (PMV) calculated using the 'Standard' effective
temperature and the Pierce two-node thermal comfort model.
- Pierce Discomfort Index
(DISC) - the Discomfort index calculated using the Pierce two-node
thermal comfort model.
- Pierce Thermal Sens. Index
(TSENS) - the Thermal Sensation Index (PMV) calculated using the
Pierce two-node thermal comfort model.
- Kansas Uni TSV -
the Thermal Sensation Vote (TSV) calculated using the KSU two-node thermal
comfort model.
- Discomfort hrs (summer
clothing) - the time when the zone is occupied that the combination
of humidity ratio and operative temperature is not in the ASHRAE
55-2004 summer
clothes region.
- Discomfort hrs (winter
clothing) - the time when the zone is occupied that the combination
of humidity ratio and operative temperature is not in the ASHRAE
55-2004 winter
clothes region.
- Discomfort hrs (all clothing)
- the time
when the zone is occupied that the combination of humidity ratio and operative
temperature is not in the ASHRAE 55-2004 summer or winter
clothes region.
More on Comfort Analysis...
Fabric and ventilation
- Glazing -
the total heat flow to the zone from the glazing, frame and divider of
exterior glazing excluding transmitted short-wave solar radiation (which
is accounted for in Solar Gains Exterior Windows
below).
For windows without
an interior shading device this heat flow is equal to:
+ [Convective heat flow to the zone from
the zone side of the glazing]
+ [Net IR heat flow to the zone from zone
side of the glazing]
– [Short-wave radiation from zone transmitted
back out the window]
+ [Conduction to zone from window frame and
divider, if present]
Here, short-wave radiation is that from lights
and diffuse interior solar radiation.
For windows with
an interior shading device this heat flow is equal to:
[Convective
heat flow to the zone from the air flowing through the gap between glazing
and shading device]
+ [Convective heat flow to the zone from
the zone side of the shading device]
+ [Net IR heat flow to the zone from the
zone side of the glazing]
+ [Net IR heat flow to the zone from the
zone side of the shading device]
– [Short-wave radiation from zone transmitted
back out the window]
+ [Conduction to zone from window frame and
divider, if present]
- Walls - Sum of heat gains to the zone
from external wall inner surfaces.
- Roofs - Sum of heat gains
to the zone from external roof inner surfaces.
- Ceilings - Sum of heat gains
to the zone
from ceiling inner surfaces.
- Floors - Sum of heat gains
to the zone
from internal floor inner surfaces.
- Floors (ext) - Sum of heat gains
to the zone
from external floor inner surfaces (e.g. floor
in cantilevered space, roof eaves etc, not ground floors).
- Ground floors -
Sum of heat gains
to the zone from ground floor inner surfaces.
- Partitions
- Sum of heat gains
to the zone from internal partition inner surfaces.
- Doors and Vents
- Sum of heat gains
to the zone from door and vent inner surfaces.
- External Infiltration
- heat gain through air infiltration (non-unintentional air entry through
cracks and holes in building fabric) when using Scheduled
natural ventilation option.
- External Natural Ventilation
- heat gain due to the entry of outside air through natural ventilation,
as defined on the HVAC tab, when using Simple
natural ventilation option.
- Internal Natural Ventilation
- heat gain from other zones due to air exchange through open internal
windows, doors, vents, holes and virtual partitions. This output also includes the thermal impact of any Interzone Airflow paths.
- External Mechanical Ventilation
- heat
gain due to the entry of outside air through the air distribution system.
You can
exclude mechanical ventilation from the cooling design calculations by
unchecking the 'Air Distribution On' Model Data.
- External Air - heat
gain due to the entry of outside air through external windows, vents,
doors, holes and cracks when using Calculated
natural ventilation option.
- Mixing Air - heat
gain due to the entry of inside mixing air through internal windows, vents,
doors and holes when using Scheduled
natural ventilation option.
Note: Surface conduction data for Walls, Roofs,
Ceilings, Floors, Partitions and Doors and Vents represents the heat conduction flow just
below the surface of the construction and so includes all surface
heat transfer mechanisms (convection, long and short-wave radiation).
Airflow
- Mech Vent + Nat Vent +
Infiltration - The sum of outside
air (in ac/h) flowing into the zone through:
- The HVAC air distribution system +
- Infiltration +
- Natural ventilation +
- Airflow through earth tubes (mechanically or naturally driven)
Note: You will usually see a small difference in air changes per hour (ac/h) between the sum of mechanical and natural ventilation and infiltration values you entered on in model data and the values reported in simulation results. This is caused by the method used to calculate and report ac/h in EnergyPlus. ac/h is reported including consideration of the air density and the exact values displayed will depend on the density of the outside air being introduced into the building relative to the density of the zone air. Cooler air is of course more dense than warmer air. More specifically, the design volume flow rate entered in ac/h is converted to mass flow (kg/s) during the simulation using the current outdoor air density. The simulated mass flow rate is then reported back out in indoor air density (for infiltration and natural ventilation) or EnergyPlus standard air density for HVAC system outside air, neither of which will ever (or extremely rarely) match the outdoor air density. So, the ac/h outputs will never exactly match the inputs. The difference between input and reported ac/h will normally be less than +/- 10%. At times when the outside air is cooler than inside there will be an underestimate of ac/h and when it is warmer there will be an overestimate. The difference between input and output values is in proportion to the difference in inside and outside air temperature.
Internal Gains
- Task Lighting -
heat gain due to task lighting.
- General Lighting -
heat gain due to general lighting.
- Miscellaneous -
heat gain due to miscellaneous equipment.
- Process - heat gain
due to process equipment.
- Catering - heat
gain due to cooking.
- Computer and Equipment
- heat gain due to computer and other IT-related equipment.
- Occupancy - sensible
gain due to occupants. Please
note that this can vary depending on the internal conditions. With
very high temperatures the sensible gain can drop to zero with all cooling
effects taking place through latent heat transfer.
- Solar Gains Exterior Windows
- (used
to be called 'Transmitted solar gains'). Short-wave
solar radiation transmission through all external
windows. For a bare window, this transmitted radiation consists of solar
radiation passing through the glass and diffuse radiation from solar reflected
from the outside window reveal, if present. For windows with a shade,
this transmitted radiation is totally diffuse (shades are assumed to be
perfect diffusers). For windows with a blind, this transmitted radiation
consists of beam + diffuse short-wave radiation that passes between the
slats and diffuse radiation from beam-to-diffuse reflection from the slats.
The heating effect of solar radiation on opaque roofs and walls is accounted
for in the Roofs and Walls fabric heat conduction data. Solar
re-reflected back out of the external window and transmitted through interior
windows is not subtracted.
- Solar Gains Interior Windows
- Total
beam + diffuse solar radiation transmission through interior
windows. Requires the 3-Full interior
and exterior solar model option to be
set.
- Zone Sensible Cooling
- is the overall sensible cooling effect on
the zone of any air introduced into the zone through the HVAC system.
It includes any 'free cooling' due to introduction of relatively cool
outside air and the heating effect of any fans present. Cooling always
shows as a negative heat gain in the results. It
is therefore not the same as a cooling coil energy delivery when
mechanical ventilation is involved. It
is best thought of as the overall HVAC cooling contribution to the zone heat balance.More on this below.
- Zone Sensible Heating
- is the overall sensible heating effect of any air introduced into the zone through
the HVAC system including any 'free heating' due to introduction of relatively
warm outside air and the heating effects of fans. It
is therefore not the same as a heating coil energy delivery when
mechanical ventilation is involved. It
is best thought of as the overall HVAC heating contribution to the zone heat balance. More on this below.
Surface heat gain data refers to heat transfer from the inside surface
of the building elements to the zone.
Note: taken
together the Internal gains and
the Fabric and ventilation data
above give an approximate Zone Heat Balance, i.e. the data represents all
of the heat flows into and out of the zone.
Technical Note
It is important to understand when looking at the Zone heat balance
data that the values do not necessarily add to exactly to zero. Factors which have a bearing on this are:
- Solar radiation values reported by EnergyPlus
are gross values and do not account
for the radiation re-reflected back out of internal and external windows.
EnergyPlus tracks solar radiation in full detail but does not report all
of the calculated values. It is not currently possible to generate net solar radiation gains from EnergyPlus.
- Also bear in mind that solar and some internal gains are mostly radiative gains and find their way into the fabric whereas the cooling is to the air. In thermal modelling terms it is not possible to make a simple heat balance of heat which is added to different parts of the thermal network.More specifically, heat transfer gains between the zone and the surfaces
cannot be added directly to ventilation gains because they are to different
'points' in the zone heat balance (surface heat transfer is to the 'rad-air'
point and ventilation is to the 'air' point).
- Minor EnergyPlus inaccuracy in reporting of conduction
through window frames causes a minor error (~1%) in Glazing heat gain
reported values. This does not affect the rest of the simulation, it is
just in the Glazing heat gain report.
- There are issues such as heat conduction through walls, floors, roofs etc and diurnal storage of heat in thermal mass, especially in thermally massive buildings to take into account. When doing heat balances make sure to view data over a reasonable period (> week) to avoid such thermal storage issues.
System Heat Flows
These heat flows are plotted on the System Energy axes:
- Zone Heating - energy
supplied by local room heaters and reheat coils to maintain room internal
heating temperature setpoint temperature when using Detailed HVAC data.
- Radiant + Convective Heating - energy provided by heated floors to the floor construction. Check the Ground Floors and Internal Floors zone heat balance outputs to see the heat transfer from the floor to the zone itself.
Total Cooling is the rate at which total energy (sensible
and latent) is removed from the mixed outside and return air stream in
order to bring the mixed air stream to the specified
temperature and humidity ratio of the supply air stream. Total Cooling also includes any cooling energy provided by radiant cooling systems. - Sensible Cooling is the rate at which sensible energy is removed
from the mixed outside and return air stream in order to lower its temperature
to the specified temperature of
the supply air stream. Any energy needed for moisture addition or removal
is ignored.
A common question from new users
"What is the difference between Zone Sensible Heating/Cooling (on the Heat Balance graph) and Zone Heating, Sensible/Total Cooling (on the System Energy graph)?" The Zone Sensible Heating is the heating effect of the HVAC system action on the zone heat balance, or in other words, the heating effect of introducing air that is warmer than the zone air. Likewise Zone Sensible Cooling is the cooling effect of the HVAC system on the zone. Note that these are not always directly related to heating and cooling coil energy delivery, especially because of the effect of free cooling from outside air. So for example even if there is no cooling coil operational at a particular time, the Zone Sensible Cooling output on the Heat Balance graph can be high due to introduction of relatively cooler outside air into the space through mechanical ventilation. These Zone Sensible Heating/Cooling outputs will also include a component due to fans (if operational) which will tend to warm air that moves through it. The Zone Heating data in the System energy graph is the energy provided by zone heating equipment such as reheat coils and radiators/baseboard units. Likewise Sensible and Total Cooling report the sensible and total energy transferred by cooling coils to the air stream.
- Zone Heating - energy
supplied by local room heaters and reheat coils to maintain room internal
heating temperature setpoint temperature when using Detailed HVAC data.
- Preheat - energy
supplied by preheat coils to temper the outside air before it enters the
outside air mixing box when using Detailed HVAC data.
- AHU Heating - energy
supplied by the AHU heating coil when using Detailed HVAC data.
- Chiller Load - cooling energy supplied by the chiller.
- Total Cooling -
at building level: sensible +
latent cooling transfer to the supply air from the AHU cooling coil +
any single zone unitary and fan coil units in the building. At zone
level: sensible + latent cooling transfer to the supply air from
a single zone unitary or fan coil unit. Note that any differences between Total Cooling and Chiller Load outputs are typically caused by the thermal inertia of the water in the chilled water loops. These differences will be most noticeable for data at hourly and sub-hourly intervals.
- Sensible Cooling -
sensible only cooling transfer from the cooling coil to the supply air.
Latent coil heat can be calculated as the difference: Total
Cooling - Sensible Cooling.
- Heat Recovery Sensible
Cooling - the sensible
cooling rate of the supply air by the heat exchanger. This rate is determined
using the supply air mass flow rate through the heat exchanger unit, the
supply air inlet and outlet conditions, and the specific heat of the inlet
supply air. A positive value is reported if the supply air is cooled by
the heat exchanger, else the rate is set to zero.
- Heat Recovery Total Cooling
- the total cooling rate
of the supply air by the heat exchanger. This rate is determined using
the supply air mass flow rate through the heat exchanger unit, and the
enthalpy of the supply air entering and leaving the unit. A positive value
is reported if the enthalpy of the supply air is decreased by the heat
exchanger, else the rate is set to zero.
- Heat Recovery Sensible
Heating - the sensible
heating rate of the supply air by the heat exchanger. This rate is determined
using the supply air mass flow rate through the heat exchanger unit, the
supply air inlet and outlet conditions, and the specific heat of the inlet
supply air. A positive value is reported if the supply air is heated by
the heat exchanger, else the rate is set to zero.
- Heat Recovery Total Heating
- the total heating energy added
to the supply air by the heat exchanger.
Building Level Only
Fuel breakdown
The data for fuel consumption for building level broken down by end-use:
Fuel totals
Total fuel consumption for building, data available at building level
only:
- Electricity -
total building electricity consumption.
- Gas - fuel consumption total
building gas consumption.
- Oil -
total building or oil consumption.
- Solid -
total building solid fuel consumption.
- Bottled gas
- total building gas consumption.
- Other fuel consumption
- total consumption of all other fuels.
CO2 emissions
Total carbon dioxide emission for building, data available at building
level only:
- CO2 emissions
- total CO2 emissions mass. This is calculated from fuel consumption totals (above) and the fuel emission factors for the region.
Site Weather data
Weather data stored at the site level and derived from the hourly weather
file:
- Outside
Dry-Bulb Temperature
- Outside
Dew-Point Temperature
- Direct
Normal Solar
- Diffuse
Horizontal Solar
- Wind
Speed
- Wind
Direction
- Atmospheric
Pressure
- Solar
Altitude
- Solar
Azimuth
Note: Although
Site weather data is stored at the Site level, it can be displayed at
Building, Block, Zone, Surface and Opening levels too.
Hourly and Sub-Hourly Results Times
The times on the x-axis for hourly and sub-hourly results refer to the time at the end of the period. So for example hourly results data for 10am refers to the period 9am to 10am.
Note also that the x-axis times in the results refer to "standard" time without any daylight saving correction applied and not the "clock" time used in schedules. This means that when viewing gains results (for example) in the summer periods with an hour of daylight saving time applied you will see the gains starting an hour earlier than in the winter.
Time values that appear in schedules refer to clock time and, while the gains would be simulated as starting at the same (clock) times as defined in the schedules in summer and winter, you may see what at first sight seem like discrepancies between scheduled start/end times and outputs until you consider the points above.