Retrotec USACE - Manual (Page 117)

Appendix A A3
Categorizing buildings by the age of construction is useful, because it can help
to group buildings with similar envelope and mechanical designs and provide
clues to typical values related to missing data. The age of construction also
allows for an understanding of the current technologies within the building.
As an important aspect of building portfolio analysis is deciphering the cur-
rent state of energy effi ciency within a building, it is necessary to compare the
specifi cations of a building at its given state with the state of the art in techno-
logical advancement.
If a single Canadian building is classifi ed in an archetype that includes a
construction date prior to 1950, then estimations of building envelope proper-
ties and mechanical systems can be made. For example, a pre-1940s building
may have a typical wall U value of 0.8 W/m
2 × C, but when compared to a more
modern building a typical wall U value could be closer to 0.2 W/m 2 × C. By this
simple comparison it can be seen that insulating the walls of a pre-1950s build-
ing would help bring energy consumption characteristics in line with current
building standards.
The diffi culty in using a single archetype for grouping is that there are vari-
ous possible fl uctuations in building design within a given archetype. Buildings
of the same age may vary widely in terms of volume of conditioned space, oc-
cupancy, schedules, and HVAC systems. For these reasons, for larger building
portfolios, it is necessary to create subgroups within each primary archetype.
Multicategory archetypes combine several building characteristics and
may consist of two or more combinations. Using age, size, and location as a
base for all categories is a good starting point for establishing this grouping
strategy. Furthermore, incorporating scheduling, fuel sources, and heating/
cooling system types will allow for a true understanding of multiple building
comparisons to be made.
A.2.2 Method(s) for Determining the Energy Consumption
of Buildings
There are at least two approaches for determining the energy consumption of
the building portfolio. The fi rst approach is to review all energy bills for the
past three to fi ve years in order to establish a trend. If the buildings’ energy
consumption is available in a database, then analyzing the energy consump-
tion of the buildings can be straightforward. However, such an approach is
limited, as it cannot predict the effects of ECMs on the energy consumption.
The second approach includes the use of building modeling tools such as En-
ergyPlus or FEDS to estimate the energy reduction due to ECMs.