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.
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
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.
inking two distinct building sets together allows greater flexibility in modeling complex building geometries or uses. Linked buildings are designed to model two buildings that share a common wall or are stacked on top of one another. Specifying that the buildings are linked directs FEDS to automatically (based on the geometry information for each building) determine the wall area (or roof/ceiling area) that is shared, and thus not exposed to exterior conditions. It essentially calculates the portion of each buildings shell that is an adiabatic surface (i.e., does not experience conductive heat transfer) and does not receive solar gains. It uses this information in load calculations to appropriately account for the impact of the buildings being connected. There are some rules, however, that must be satisfied in order to link building sets. First, both sets must contain the same number of buildings so that a direct one-to-one linking is achieved. Second, both sets must have the solar normalization turned off (calculate solar gains by facing direction). Also, FEDS currently does not model cantilevered buildings so for top/bottom linking, the N/S and E/W lengths of the top building must not be greater than the corresponding lengths of the bottom building.
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.
Prototype buildings in FEDS are modeled as basic rectangular blocks, with the actual geometry calculated based on the total floor area, number of floors, floor-to-floor height, and aspect ratio. However, additional geometries can be modeled by using the linked building approach or through the advanced geometry inputs, which allow modification to underlying parameters including window/wall/roof/floor areas and conditioned air volumes.
The advanced geometry inputs allow for more flexibility in modeling non-standard building geometries compared to the linked building approach. When accessing the advanced geometry inputs, the user may specify or alter a number of geometric parameters for each zone of the building to customize the resulting model. For example, the exterior wall areas and window areas can be specified for the north, east, south, and west sides of each zone. Additionally, roof, floor, footprint areas, exterior perimeter length, and conditioned air volume can be specified for each zone. These adjustments provide users with the ability to model a number of more complex geometries, such as individual parts of a strip mall complex or varying window fractions for different sides of a building, with greater accuracy than through other means. The option can be accessed via the button on the regular geometry inputs screen.
Solar normalization is used when the orientation of a single building is unknown, does not align with N/S/E/W directions, or when there are multiple buildings of differing orientations in a building set. It can be used to avoid biasing the solar gains calculation by normalizing the exterior wall, window, and roof areas, such that the resultant loads are roughly the average of two buildings: one with an east/west orientation and one with a north/south orientation. FEDS can be set to "ignore facing directions" to use solar normalization.
The aspect ratio is used to define the geometric orientation of the buildings in a building set. It is a ratio of length to width and is calculated by dividing the typical north-facing length by the typical east-facing length.