[Bldg-sim] Percent Energy Savings

[Andy hoover]

The highlighted yellow and that entire paragraph nail it for me.  It results
in showing/taking the most effective steps to decrease energy usage which
should be the objective, regardless of percentage.  Percent savings is
always very very subject to manipulation.

 

Andy  

 

Andy Hoover

Principal

The BEST Consultant, Inc.

Office: 678-200-7648

Fax:678-827-0574

Cell: 678-793-1159

 

www.thebestconsultant.com

 

 

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Varkie C Thomas
Sent: Wednesday, March 04, 2009 11:04 AM
To: Varkie C Thomas
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Percent Energy Savings

 

I received a few responses to this message from outside the USA sent
directly to me.  Below is the message again with some additional points in
red.  The sections highlighted in yellow is from one of the responses


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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Varkie C Thomas
Sent: 2009-03-03 18:26
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Percent Energy Savings

 

ASHRAE Std90 for the baseline is already stringent and specifies the
commonly used systems & plants based on building type and size.  Based on
the CCGT building, high percentage energy savings for LEED certification can
be achieved with low-rise buildings with a high exposure to floor surface
areas to locate PV panels, high but efficient glass to wall area for
day-lighting, the use of GSHP (which requires a large site area which may
not be available in city blocks), and low common energy consuming systems in
baseline and proposed which increases "percentage" energy savings.  

 

A school building is low-rise, is low in process loads (increases % savings)
and is high in occupancy ventilation which allows for air-to-air heat
recovery. It operates only during the day increasing the impact of
day-lighting. It is closed in summer, reducing the annual cooling load and
increases the impact of solar heating during the rest of the year in cold
climates.  So it is possible to achieve zero energy usage.  

 

The choices are limited in the case of inner city high-rise buildings.
Today's high-rise office building design tries to maximize the glass
percentage which increases the impact of day-lighting.  The glass could have
PV properties with a very small overall efficiency of converting light to
110V electricity.  The ASHRAE Std90 baseline for Systems and Plants for such
a building is considered normal design.  UFAD and other options are not
typical.  The proposed envelope has to offset the 40% Window-Wall-Ratio
specified by ASHRAE.  If the office building envelope is used for a hospital
or hotel, which operate 8760 hours/year, then the percent energy savings
will go down.  

 

High percent energy savings does not therefore necessarily mean a better or
optimized designed building in terms of the client's interests.  Percent
energy savings should therefore not be the criteria for energy efficient
building design.  It should be based on Energy Conservation Measures (ECM)
used for the given building that are more energy efficient compared to
ASHRAE Std90 for the given building type and size which usually results in
increased first costs. The ECMs are going to be different for different
types of buildings in different locations.  If the ECM used is
inappropriate, then the client pays a price for the high percent energy
savings.

 

In my opinion the way to express energy efficiency would be energy per unit
area.  Occupancy per unit area has to be defined for different types of
buildings (office, hotel, retail, hospital, etc.) and energy efficiency
should also take into account location based on HDD & CDD.  Energy per
Person will account for overall energy efficiency of buildings &
transportation when designing sustainable townships.

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