User manual

FAQ for CBECC-Res 2013
11
FAQS POSTED ON NOVEMBER 21, 2014
1. There is still a watermark on my Existing+Addition CF1R, but no HERS measures. What am I doing
wrong?
The first recommendation is to see if you have modeled AC Charge (refrigerant charge) as “Verified”
(even on an existing system or a “no cooling equipment” system this can trigger HERS). If so, change
it to “Not Verified” and this should solve the problem.
2. With regard to whole house fans, the CBECC-Res User Manual says the attic ventilation
requirement is 1 square foot for every 1,000 CFM of whole house fan air flow, but the prescriptive
requirement is 375. Which requirement is correct?
The requirement is 1 ft
2
for every 375 CFM of whole house fan air flow. The Standards are part of a
rulemaking so any time there is a requirement in the Standards, it is the requirement that must be
followed. Since the standard design is based on the prescriptive requirements (including Section
150.1(c)12), if a person chooses to model a whole house fan, the prescriptive criteria apply. CBECC-
Res is modeling the correct ventilation requirement. The software user cannot modify this value.
The User Manual will be updated as soon as possible.
3. Can I model a single family residence with more than three stories in CBECC-Res?
Yes, since all single family buildings regardless of height are low-rise residential, you can use CBECC-
Res for compliance (the three-story limit does not apply to Occupancy Group R-3). The program
input is limited to 3 stories to avoid any confusion on the part of users.
4. If I am modeling an existing+addition, how do I handle a radiant barrier installed for the addition
only? [Replaces Question #6 from 10/20/14]
Beginning with version 3b, you can model a second attic zone over the addition that has a
construction that includes a radiant barrier. If, as mentioned in the October 20 Question 6, you are
not upgrading the existing building to install a radiant barrier, this is the correct way to model that
condition.
5. When modeling multi-family buildings, are there any new details I should be aware of?
Beginning with version 3b, the reporting for multi-family dwelling units is modified to accommodate
the needs of HERS Raters. This means every dwelling unit is identified on the CF1R. Since the
program makes associations with the HVAC system and the dwelling unit automatically, we
recommend using very short names for the heating, cooling, distribution, and fan system names in
the Dwelling Unit Types. Otherwise when the program combines these names it could quickly run
out of available space in the fields on the CF1R (this recommendation is also noted in the User
Manual, Section 5.6).
6. When I model my existing duct location it triggers a HERS requirement. Is that something that can
get fixed?
It is a known issue. In the meantime, since the ducts are existing, put them in another location (if
there is an attic, this is commonly referred to as a default location).
FAQS POSTED ON OCTOBER 20, 2014
1. Are there any tips to help me find what is causing a watermark on an addition that should not
have a watermark?