User manual

FAQ for CBECC-Res 2013
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3. Will we be able to model other shading devices soon?
Not any time soon. ASHRAE Window Attachment (used in CBECC-Res) does not use SHGCs and only
has bug screens. At some future time when rules and programming can be developed, the ability to
model advanced systems such as operable exterior shades may be added.
4. Do I really need 6 surfaces in every zone?
Yes. You can add interior surfaces if necessary.
In the future, we’ll try to add a more detailed explanation to this FAQ, but for now here’s a basic
explanation: CBECC-Res uses very advanced modeling algorithms. The program sets up a radiant
network without knowing the detailed geometry of every surface and object in the building by using
a very clever algorithm that approximates zones as spheres. In order for the algorithm to work
mathematically it needs at least 6 surfaces that can be resolved into a box (but there is no box
involved in the calculation). There are also several other ways this algorithm can fail mathematically,
including if the area of one surface is larger than the total area of all the other surfaces (which also
cannot be resolved into a box).
When we started testing CBECC-Res (particularly when we added garages) we kept getting
complaints from testers who getting generic crash message and they couldn't see anything
wrong. We tried to improve things by the very simplistic 6 surfaces filter, which catches a majority of
the problem cases.
FAQS POSTED ON NOVEMBER 20, 2013
1. I’m concerned about the speed of run times in CBECC. Is there a reason we cannot have an option to
run CBECC-Res with reduced weather to speed up the processing time?
This could create unexpected consequences and the CEC does not have the staff resources to study
any such consequences. As an alternative, CBECC-Res will soon have a "batch processing" function,
which will allow users to set up a series of runs to launch without any user requirements between
runs. With this option, and a global reduction in analysis run time, users should be able to be
productive with their time.
2. Regarding Zonal Control, if I specified the building meets zonal control criteria under the building tab,
why is there also a check box on the cooling system screen?
This check box is to enable modeling the exception for zonally controlled systems with a bypass duct
to only meet 150 CFM/ton. The 150 CFM/ton (an energy penalty) does not have to be verified by a
HERS Rater, however any level higher than 150 CFM/ton for a zoned system and any if you want to
include a bypass duct and not meet 350 CFM/ton.
3. What are the watermarks that could potentially appear on the CF1R and how can I get it to change?
A recent change will result in one of two potential watermarks on the PDF of the CF1R. First is for
certified software with a valid “signature” (security check), the watermark will read “This Certificate
of Compliance is not registered” and second is for submissions using an open source ruleset that
does not provide a certified key (security check) which will read “Not useable for compliance. For
example, if the authenticity of the software cannot be verified, or if the PDF was manually
generated from the tools menu rather than as a part of the compliance analysis, the second
watermark will appear.