CABO's MEC (1992, 1993,
1995)
Regulatory
requirements:
The
1992 and 1993 CABO Model Energy Codes required that U-factors
for fenestration products be rated, certified and labeled in accordance
with NFRC 100. In the absence of NFRC rated U-factors, a table
of U-factors for different window types with a limited number
of options was provided.
In
the 1995 version, a requirement for Solar heat Gain Coefficient
SHGC) was added. Fenestration products must be tested and documented
by the manufacturer in accordance with NFRC 200 or utilize a default
rating.
In
addition, maximum air leakage rates were referenced for various
window products in accordance to different association standards.
Prescriptive
Requirements
All
three versions of the CABO-MEC established fenestration performance
requirements based on fenestration area (expressed as a percentage
of the gross wall area) and climate zone. The Model Energy Code
established nineteen climate zones and provides tables for each
zone for both single family and multi-family buildings. The 1992
and 1993 versions set fenestration U-factors anywhere from no
requirement to less than 0.35. The 1995 version used the same
prescriptive packages and climate zones and introduced requirements
for SHGC ranging from no requirement to less than 0.40. Credit
was given for overhangs providing shading to windows.
A
trade-off option was provided using an equation to evaluate the
impact of any change to the prescriptive approach had on the overall
thermal performance of the building envelope. For xample, more
window area could be used, but only if additional insulation was
provided for the ceilings, walls, floor or foundation.
Unglazed
doors did not have to meet any thermal requirements as long as
they were limited to 5% of the wall area. Skylights only had to
meet minimum U-factor requirements, but were limited to 3% of
the roof area.
System
or Design Requirements
The
CABO's Model Energy Code offered an alternative compliance path
called the Software Approach. A computer program, MEC-CHECK, was
developed by the federal government to provide an automated approach
for trade-offs and incorporate additional features to make CABO's
MEC more flexible. This software is free from the federal government
and is available on the web at:
http://www.energycodes.gov/
.
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