ASHRAE Journal - February 2014 - 68

COLUMN ENERGY MODELING
Jared A. Higgins

New 90.1 and Modeling
BY JARED A. HIGGINS, P.E., MEMBER ASHRAE

Every three years I look forward to the release of the newest version of ASHRAE/
IES Standard 90.1. As an engineer by trade, I always check the new building envelope requirements, mechanical system efficiencies, and reductions in lighting
power. Additionally, as an energy modeler, I always turn to Normative Appendix
G to see what is going to change for the performance rating method. Needless to
say, there are plenty of changes that have occurred since the 2010 version.
I would say that the 2004 version of Standard 90.1 was
the beginning of when a large number of professionals
became involved with energy modeling. There were several changes that occurred in the 2007 version including
the baseline building vertical fenestration percentages,

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calculating the baseline building HVAC supply fan power,
and airside economizer requirements. However, there
was not a big change between the 2007 and 2010 versions.
The main changes were the values for roof solar reflectance and thermal emittance, adding two additional baseline HVAC systems for heated and ventilated-only storage
buildings, and defining the requirements when using
purchased chilled water and hot water or steam. Now,
with the release of the 2013 version, once again there are
several changes. The highlights are summarized below:
Baseline Vertical Fenestration Area now has a table
that defines the amount of glazing to be modeled in the
baseline building. However, there are only certain types
of buildings listed. If a building type is not listed, then
the glazing is distributed in the same amount as the proposed building or the maximum allowed in the technical section, whichever is less. Additionally, the proposed
building has multiple building types in the design; the
percentages in the table shall match each building type.
Skylight modeling requirements are now defined for
the baseline building.
Distribution Transformers are now required to be
modeled in both the proposed and baseline buildings.
This is only applicable when low-voltage dry-type distribution transformers in the proposed design exceed the
efficiency listed in the table in the technical sections. If
the transformers only meet the efficiency requirements,
they need not be modeled.
Jared A. Higgins, P.E., leads the mechanical engineering and energy services group for
Parkhill, Smith, & Cooper, Lubbock, Texas. He is an ASHRAE certified Commissioning
Process Management Professional.

ASHRAE Journal - February 2014

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