ENERGY STAT: THE AVERAGE ENERGY STAR CERTIFIED BUILDING USES
35% LESS ENERGY AND CAUSES 35% FEWER GREENHOUSE GAS EMISSIONS THAN SIMILAR BUILDINGS.
Understanding Zero Energy Buildings
➙There’s more to verifying zero energy buildings than just noting that renewable
energy production offsets annual con-
sumption requirements. The definition of “zero
energy” differs between regions and organizations,
creating confusion over exactly which buildings
have truly earned the moniker.
A new report by the DOE, A Common Definition
of Zero Energy Buildings, seeks to bring building owners, FMs, government agencies and other
stakeholders onto the same page regarding zero
energy targets. “A commonly accepted definition
and corresponding methods of measurement would
also have a significant impact on the development
of design strategies for buildings and help spur
market uptake of such projects,” the DOE adds.
To properly determine which buildings qualify
as zero energy, the research team had to answer
What is the site boundary? This represents a
meaningful boundary of all areas that are func-
tionally part of the building. This is usually the
property boundary, but could be restricted to just
the building boundary if the on-site renewables are located
within its footprint. The site boundary must include the point
of utility interface and encompasses all on-site renewables, all
energy that is delivered to the building or exported from it, and
all energy consumption and production within the building.
How is energy accounted for and measured? Certifying a
zero energy building requires a thorough understanding of all
energy delivered to the building and exported to the grid on an
annual basis. “A zero energy building may only use on-site renewable energy in offsetting the delivered energy,” the report
explains. “Renewable fuels delivered to the site boundary are
not included in this term because they are treated as delivered
energy to the building. For example, wood chips or biofuel harvested on-site would be considered on-site renewable energy,
while wood or biofuel delivered to the site would not.”
How is source energy calculated? “Most building managers are familiar with site energy, the amount of energy
consumed by a building as measured by utility meters,” the
report explains. “Site energy … does not tell the whole story of
impacts from resource consumption and emissions associated
with energy use.” Site energy consumption is an especially
poor metric for buildings with multiple energy types, on-site
generation or co-generation units,” the report explains.
To determine the full impact of all energy use, all types of
energy must be converted into equivalent units of raw fuel
consumed in generating one unit of energy that is consumed
on-site. The report offers a source energy conversion factor so
that all sources from imported grid electricity to natural gas,
steam, and water can be factored into zero energy accounting.
To learn more about how buildings qualify as zero energy,
12 FREE INFO: Circle 108 on Reader Service card or Buildings.com/freeinfo
DEFINING THE SITE BOUNDARY is the first step in determining whether a building’s net
zero energy claim is accurate.