[BLDG-SIM] Energy Cost Budget (ECB) Method & LEED

Varkie Thomas Varkie.Thomas at som.com
Mon May 17 10:27:44 PDT 2004

When comparing standard design based on ASHRAE ST90 and a proposed
design for LEED points under "Optimize Energy Performance" using the ECB
method, can the fuel types in both cases be made the same?  Does STD90
ECB method require natural gas equipment to be used for the standard
design if it produces lower energy costs?  
For example, three years ago, gas prices were at a record high and
electricity was relatively cheaper.  So a building was designed based on
all electric equipment.  The proposed design saved about 30% in energy
usage per year and about the same in cost over the standard design
(electric or gas).  
Gas prices have since dropped significantly. The proposed design still
saves about 30% in energy compared to standard design.  The energy cost
of the proposed all-electric design is now higher if it is compared to
the standard design based on current natural gas rates.  Can the
proposed electric design be compared to the standard model that also
uses all-electric equipment for LEED points? 
On page 63, Table 11.4.3A, Budget System Descriptions of ASHRAE
Std90-2001, System-1 is VAV with parallel fan-powered boxes and electric
resistance heating (electric) and System-2 is VAV standard boxes with
hot water heating using fossil fuel boiler (gas).  If the proposed
design used System-1 (electric) then can the standard be System-1
although System-2 will use less energy and also cost less?
In comparing energy costs, does LEED consider the difference in source
energy efficiency between gas and electric?  What about long-term
reliability?  Electricity can be generated using a variety of fuels
including nuclear, whereas natural gas resources are limited and the
costs will therefore increase in the future with diminishing supplies.  
Is the purpose of the Energy "Cost" Budget method to reduce the energy
demand based on TOU rates?  Is the comparison between standard and
design for LEED points based on conditions at the time of design or at
the time of occupancy? Does ECB consider future fluctuating gas and
electric rates?  Shouldn't there be a LCCA comparison of energy costs of
standard and proposed design using the DOE/FEMP future escalation rates?
Is it realistically possible to save over 60% in energy costs over STD90
design without using renewable energy such as PV-panels and GSHP?
Varkie Thomas
Skidmore, Owings & Merrill LLP
Tel: 312-360-4467 (direct)

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