Custom EPW files may be created by experienced users and imported using the "Import EPW File" option. There is also an option in FEDS version 8 that allows users to view and alter the weather data (e.g., drybulb temperature, relative humidity, atmospheric pressure, and sky clearness). This is presently intended to allow users to make weather adjustments to be used when calibrating a model to conditions for a specific base year. Contact FEDS support for more information.
Yes. FEDS now provides an option to import additional weather station data. An "Import EPW Weather File" feature enables users to access the growing number of weather station data representing many locations globally, as well as more recent records of typical climate data, and even data covering specific time periods or energy modeling scenarios. All data must be in standard EPW file format. Refer to the FEDS User’s Guide for more information.
No. FEDS infers parameters based on the most likely current condition of a building and its equipment. Inferences for an 1820 vintage building will reflect the typical improvements and upgrades that have occurred over time.
Weekday, Saturday, and Sunday hot water consumption values are determined using typical usage rates for a given use-area type, along with the number of occupants and occupancy schedule for each day type. Values are also adjusted according to such parameters as the presence or absence of showers and high efficiency fixtures.
During a month that has been identified as seasonally unoccupied (also referred to as non-operating), FEDS assumes zero occupancy, all lights are off (except exit signs), and the cooling system is shut down. Heating is operated at a reduced level generally for the purpose of preventing the pipes from freezing (temperature kept at low setpoint specified by the unoccupied season thermostat setting). General plug loads are assumed to be non-operational, as are most motors (although this may be overridden by specifying monthly motor load factors).
Unoccupied hours or day types of occupied months are those periods during which there is reduced occupancy of the building. These are referred to as low occupancy periods in FEDS. For a typical commercial facility this might occur during the night and on weekends. A small number of occupants might be present (though less than during normal operating hours), and all energy systems remain active although they may operate at reduced levels. The operation of HVAC, lighting, plug loads, and motors are all controlled by inputs such as thermostat setpoints (enabling temperature setback), ventilation control mode, and utilization/load factors.
Full 24-hour occupancy can be specified for any day type by entering the same start and end hours (except 0 and 2400). For unoccupied day types enter 0 for both start and end times (or leave them blank). Note: if you do not specify occupancy hours, they will remain blank and FEDS will model the buildings as though they are unoccupied (reduced occupancy). Shortcut buttons are available on the standard occupancy inputs screen to make specifying continuously occupied and unoccupied day types easier.
FEDS assumes circulating (or loop) hot water systems serve entire buildings. Specifying a loop system for use-area 1 automatically identifies that it also serves use-area 2. Loop systems that only serve use-area 2 cannot be modeled, and the loop selection box is unnecessary and is disabled.
If the building is newer than the rated life of the equipment in question, then the remaining life is equal to the difference of rated life and building age. If the building is older than the equipment's rated life, FEDS assumes that on average, equipment will be halfway through their life (but users can override this assumption and specify actual equipment vintage). Rated lives vary by equipment technology. Some examples of rated lives used in FEDS are:
envelope components (windows, insulation, etc.) – 40 years
lights – typically 25 years (Although the cost of replacing lamps and ballasts is figured into the analysis based on specific replacement intervals and hours of operation)
boilers – 40 years
furnaces – 20 years
chillers – 20 years
package AC units – 15 years
heat pumps – Air Source/15 years, Ground-Coupled/20 years
motors – 15 years
hot water heaters – electric, 12 years; gas, 10 years; distributed heat pump, 12 years; central heat pump, 15 years
Storage capacity for hot water is calculated using the building type and building's design occupancy. For distributed tank systems, values are rounded up to the next increment of typical tank capacity.
No. If a building (or use-area) has any hot water available users should specify 100% of it is served by hot water. As long as there is hot water available in a space, occupants will utilize it even if it is not immediately accessible. The purpose of having the portion served input is to allow the FEDS user to specify entire buildings (or use-areas) within a building set that do not have any hot water. For example, for a building set consisting of 10 buildings in which two of the buildings have no hot water service, they would enter that two buildings (or 20%) for the portion of buildings in this set that have no water heating.
Choose a weather station that most closely represents the weather at your location. Most times it will be a city in the same state as you, but can be in a neighboring state, or in some instances in another region altogether. When specifying the zip code of the site or building(s), FEDS will recommend a weather station that offers the most similar weather to your location.
FEDS contains a built-in database of building survey data and is able to infer a number of building parameters based on the small set of required inputs provided by the user. For example, FEDS uses information such as building type, location, floor area, and vintage to determine the most likely construction type and geometry. It uses similar information along with heating fuel type and cooling equipment, to determine the most likely heating technology and ventilation system parameters for a building. All inferences enable a user to model buildings without having intimate knowledge of the detailed engineering parameters. The resulting building prototype parameter values are statistically the most likely values based on the limited set of information provided. Of course, all inferred data may be easily overwritten by simply entering (locking) a value in the user interface screens.
FEDS draws upon a number of sources to determine inferable parameter values. Major sources include national building energy consumption surveys such as the Commercial Buildings Energy Consumption, Residential Energy Consumption Survey, large end-use studies such as the End-Use Load and Consumer Assessment Program, ASHRAE handbooks, building and equipment codes and standards, and manufacturers' data and extensive building audit and evaluation experience.
A locked value, in terms of FEDS inputs, is one that the user has entered for an inferable parameter. This indicates to the model that this is a user-entered value and should not be updated (inferred). Clicking on the lock symbol can also lock a currently inferred value. When a value is locked, the lock icon will appear as a latched or closed lock. To unlock a value, simply click the icon again, changing it to an open or unlatched lock. This value will now be inferred the next time inferences are run.
Variable occupancy is an improved approach to the seasonal occupancy option which allows users to specify that certain months are non-operating (e.g., schools may be shut down over summer break). Variable occupancy also offers greater flexibility by allowing users to specify the percent of days within specific months which follow the general occupancy and operation schedule defined in the standard occupancy inputs. One hundred percent indicates the building or use area operates all days of that type during the month according the standard schedule. Zero percent indicates the building (use area) is either non-operating (shut down) or in a low occupancy state (occupied at the low occupancy and equipment use level) for all days of that type during the month. For any value between 0% and 100%, FEDS will multiply that value by the actual number of days of that type in the month and model the resulting number of days (rounded to the nearest whole day) as operating according to the standard schedule. The remainder of the days of that type in the month will be deemed either non-operating or at low occupancy (depending on the selection of non-operating period status type). As a convention, FEDS will model the first X days in the month as occupied and operating to the standard schedule, and the remaining days of that type in the month as non-operating or at low occupancy. The variable occupancy capability provides significant modeling flexibility and is particularly useful in modeling occupancy and building operation that varies within the course of a month, such as for National Guard or Reserve buildings that may only be heavily occupied on certain weekends through much of the year.
Another option for even greater control over building and use-area operation and occupancy (for each hour of the year) is also available. Contact FEDS Support for more information if interested in using this approach.
For distributed tank systems, FEDS assumes commercial tanks are 80 gallons, while residential units are 50 gallons.
FEDS assumes loop (circulating) systems serve an entire building and, therefore, the number of tanks is inferred to be one for each building, regardless of the number of use areas present.
FEDS now offers 1.116 weather station data locations, primarily from a TMY3 and CWEC sources. From this data it derives such information as heating and cooling design day conditions, hourly temperature, clearness, and humidity profiles for a typical meteorological year. See Appendix D of the FEDS User's Guide for more information.
No. All occupancy hours must be specified by the user. Failing to do so will indicate to the model that the building is operating in the unoccupied mode each day during the week.