ryan81 - Contact COMCheck support. By the way the software does not permit the default IECC glass U-values to be used. Would you like to mention that also?
When I contacted COMCheck support in 2010 because I could not get a building to pass using the 2006 IECC prescriptive values, they told me COMCheck determined compliance by the "trade-off" method, not the "prescriptive" method. As a result of my inquiry, they also then altered the COMCheck software to correct for some faults (in the energy code, I think).
Here is the string of emails. I have not wrapped my head around it completely, but I think it says the IECC was screwed up. (I changed this text to
green.) It is very possible that it is messed up again. I replaced my name with "Mech" and the support personnel names with "COMCheck Support.
" I changed the text to Bold to show where COMCheck support mentions the trade-off method and also where they said they would alter the software.
Notification of Issue Change
Issue: | [On-Line Form] IECC minimum values used, COMCheck fails design |
Issue Number: | xxxxx |
Description:
Entered on 12/27/2010 at 09:50:21 PST (GMT-0800) by COMCheck Support:
Mech,
Please note that I modified COMcheck to deal the the issue described in this email
thread.
You should now be able to enter the 'prescriptive' values for your project and get a
passing compliance.
You will need to download and install COMcheck 3.8.1 again. The build version with
the fix for this issue is "3.8.1.3".
The build version you are using is found by clicking Help->About COMcheck and looking
in the top right pane of that screen.
Let me know if there are any ongoing issues.
COMCheck Support
COMcheck Software Support
Entered on 12/16/2010 at 11:43:57 PST (GMT-0800) by COMCheck Support:
Mech,
I've had another conversation with one of our energy code engineers about this problem.
We decided to resolve it (hopefully once and for all) by calculating the required
U-factor using the prescriptive R-values for cavity and continuous insulation instead
of fetching the required U-factor from a table directly.
This is inconsistent methodology that we have tried to avoid but it is so obviously
wrong in the code language that we feel justified in taking this approach.
I will notify you when I have a new release of COMcheck out on the website.
COMCheck Support
COMcheck Software Support
Entered on 12/15/2010 at 13:25:46 PST (GMT-0800) by COMCheck Support:
Mech,
First off, you should note that COMcheck does not show compliance by the
'prescriptive' method. It determines compliance by the 'trade-off' method.
And COMcheck applies the "U-factor" requirements set forth by the energy code.
Regrettably, and I mean that seriously, the IECC code committees, for metal building
roofs, assigned requirement U-factors that couldn't be matched with the proposed
U-factor table values. You'd have to look closely at the code language of 2006 IECC
and ASHRAE 90.1-1999 and 2004 to see how this plays out.
More specifically, your project fails using the 'prescriptive' values because the
roof requirement U-0.041 is based on the "Filled Cavity with Thermal Space Blocks"
criteria (see Description and Reference columns in 2006 IECC, page 31, Table
502.2(2), Roof = R-19+R-10). But the proposed U-factor is based on the ASHRAE 90.1
criteria called "Standing Seam Roofs with Thermal Spacer Blocks, Double-Layer,
R-10+R-19", and in the ASHRAE Table A2.3 (page 81), a R-29 (R-10 + R-19) proposed
insulation is equivalent to U-0.052. So on this basis alone the proposed U-factor is
not meeting the required U-factor. And if you look at that ASHRAE table you'll also
note that you never can get the Double Layer criteria to convert to U-0.041.
This is
a serious fault in the 2006 IECC energy code.
So in order to make this project pass you have to add wall and roof insulation above
and beyond the code 'prescriptive' requirements to an extent that the walls make-up
(i.e., trade-off) for the roof shortfall. One example of this is to enter R-30 walls
and R-35 roof insulation values.
Alternatively, you could visit with your code official to explain the problem and
hopefully obtain a clearance from him/her.
Or don't use COMcheck but instead find a prescriptive compliance tool/worksheet to
show compliance.
Or, change your metal building roof to a "Other Metal Building Roof" then enter a
U-factor that you and your code official recognize as an acceptable U-factor for your
building. The 'prescriptive' U-factor would be 0.041. When I tested this last option
I noticed that there is a bug in COMcheck when specifying Other Metal Building Roof
while the energy code is 2006 IECC and the climate zone is '7'. The bug was that the
software would revert the "Other Metal Building Roof" to a metal building standing
seam type roof. This bug didn't affect the requirement you would face but it does
prevent you from simply entering a U-factor for the Other Metal Building assembly.
So I fixed this bug and recompiled COMcheck and have posted the fixed version out on
our website for you to download. The fixed version will have a 'build version' number
3.8.1.2. You can find the build version you are currently working with by clicking
the Help-About COMcheck menu option then look in the upper right hand pane. Note that
he main version number will remain as 3.8.1.
Sorry, that's the best explanation I give.
COMCheck Support
Entered on 12/07/2010 at 14:51:40 PST (GMT-0800) by Mech:
I was curious if anyone was able to determine the answer to my
questions?
Thanks,
Mech
Entered on 11/12/2010 at 09:17:26 PST (GMT-0800) by Mech:
Attached is the data file.
On a side note, the building fails by 3% with perimeter insulation.
Without the perimeter insulation, it only fails by 2%.
Sincerely,
Mech
Entered on 11/12/2010 at 08:57:51 PST (GMT-0800) by COMCheck Support:
Mech
Can you forward me your data file to review further.
Entered on 11/10/2010 at 14:46:12 PST (GMT-0800) by Mech:
Priority=3
Status=Open
COMCheck 3.8.0
Project is located in Superior, WI, Zone 7 per the 2006 IECC.
I input values for a metal building with a 1,738 sqft standing seam metal roof with R29 cavity insulation, 3,248 sqft of wall area with R26 cavity insulation, 149 ft slab perimeter insulated to R15, and no doors. I used the minimum values required by the Energy Code, but the building fails by 2%. Why does COMCheck fail the building with minimum Energy Code values? Did I enter something incorrectly?
Thank you for your assistance.
Attachments: ProcessBldg#2.cck
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