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

Jason Glazer jglazer at gard.com
Tue May 18 10:38:37 PDT 2004


Figure 11.4.3 and Table 11.4.3.a in ASHRAE Standard 90.1 
Section 11 together show that the heating energy source for 
the proposed design and the energy cost budget building 
should be the same type: electric resistance is compared 
against electric resistance, heat pumps against heat pumps, 
and fossil fuel is compared against fossil fuel.  This 
approach in the Standard is intended to be "fuel neutral" 
and not penalize any fuel selection during the building 

A proposed design using multizone commercial building using 
a cooling system with a cooling tower maps to an energy 
cost budget using Figure 11.4.3 as System 1, VAV with 
parallel fan powered boxes with electric resistance.

As far as the use of Section 11 in LEED, I know that they 
have other provisions so you should review those carefully, 
my comments are related to Standard 90.1 only.

Trying to answer some of your other questions. ECB's 
purpose is a fair treatment of designs that don't meet all 
of the prescriptive sections of the standard but exceed 
requirements in other sections. It is not demand oriented 
at all but energy cost oriented.  ECB uses actual utility 
tariffs that are approved by the adopting authority. In the 
case of LEED, that would be USGBC.  TOU may or may not be 
acceptable, ask USGBC. Fluctuations in rates are a reality 
but I would suggest the rates that would be submitted are 
in affect when the application is submitted. No LCCA 
analysis is need since ECB is just looking at matching 
annual energy costs for a single year. 

I would be very suspicious of 60% savings over 90.1 unless 
some very significant investment is made in energy 
efficiency in the building.  I may be possible without 
PV/renewables but it would be difficult.

Hope this helps


On 17 May 2004 at 13:27, Varkie Thomas wrote:

> 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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Jason Glazer, P.E.  jglazer AT gard DOT com  847 698 5686
GARD Analytics - http://www.gard.com/
1028 Busse Highway, Park Ridge, IL 60068
Building Energy Simulation and Analysis
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