<font size=2 face="sans-serif">Hi John,</font>
<br>
<br><font size=2 face="sans-serif">I have attempted to answer your questions
from the two emails copied below starting with the email from Tuesday.</font>
<br>
<br><font size=2 face="sans-serif">Tuesday Email:</font>
<ol>
<li value=1><font size=2 face="sans-serif">Yes. Note that for VAV systems
it may be sufficient to set the block airflow in the Create Systems - Advanced
window.</font>
<li value=2><font size=2 face="sans-serif">The VAV box will still modulate
assuming the Clg VAV min in the VAV control section of the Create Rooms
- Airflows window is set to less than 100%, as it is in the screen shot
that you provided.</font>
<li value=3><font size=2 face="sans-serif">Assuming the pretend building
you are referring to is the ASHRAE 90.1 Appendix G Baseline alternative,
than you should not manually change these cfms to match the design. Instead,
the Baseline airflow is required to be autosized based on a 20 degree delta
t between the design cooling supply air temperature (set both the Cooling
Supply Max and Min values in the Create Systems - Design Temperatures window)
and the design cooling setpoint for the spaces served by the system. Note
that the Main Cooling coil capacity units on the Create Systems - Heating
and Cooling Coil Overrides window should be set to % of Design Cooling
Capacity instead of % of Design Capacity by Adjusting Airflow.</font>
<li value=4><font size=2 face="sans-serif">Enter the scheduled pump motor
values.</font>
<li value=5></ol><font size=2 face="sans-serif">Wednesday Email:</font>
<ol>
<li value=1><font size=2 face="sans-serif">I normally set the Baseline
model outdoor airflow manually by setting Apply ASHRAE Std62.1-2004/2007
field to No and entering the average ventilation airflow per square foot
into the Cooling and Heating ventilation inputs. I calculate the ventilation
airflow per square foot by taking the total design outdoor airflow associated
with each Baseline system and dividing by the sum of the floor area of
the spaces served by that Baseline system. The only issue you may run into
is if you have a system with a minority of rooms with a high percentage
of OA to SA ratio and by averaging the OA over every room served by that
system you end up with a lower VAV minimum for those outlier rooms, but
this is conservative, therefore the reviewer shouldn't have a problem with
it.</font>
<li value=2><font size=2 face="sans-serif">In response to your side note:
You should make sure that your Proposed Case model reflects the design
and that the Baseline Case model has constant ventilation airflow independent
of the hourly supply airflow of the VAV system. Note that to get TRACE
to model constant OA in a VAV system, the Fixed return / outside air dampers
box located in the Advanced Options sub-window of the Create Systems -
Options window must be unchecked. Also, if the design has a fixed % of
OA (such as the 30% mentioned in your email), ensure that the minimum 62.1
required ventilation is still supplied during the minimum expected VAV
box position during the course of the annual simulation to comply with
Section 5.4 of ASHRAE 62.1-2007.</font>
<li value=3><font size=2 face="sans-serif">You could do that, or see my
response to question #1 above.</font>
<li value=4></ol><font size=2 face="sans-serif">I hope that helps and good
luck!</font>
<br><font size=2 face="sans-serif">Alex</font>
<br>
<br><font size=2 color=#3f803f face="Arial"><b>Alex N. Chapin</b></font>
<br><font size=2 color=#5f5f5f face="Arial"><b>Sustainability Program Engineer</b></font>
<br><font size=2 color=#5f5f5f face="Arial"><b>SRI Green Building Certification,
LLC</b></font>
<br><font size=2 color=#5f5f5f face="Arial">300 Northpointe Circle • Suite
304</font>
<br><font size=2 color=#5f5f5f face="Arial">Seven Fields, PA 16046 • USA</font>
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<p><tt><font size=2>Date: Tue, 29 Jul 2014 15:39:04 +0000<br>
From: "Eurek, John S NWO" <John.S.Eurek@usace.army.mil><br>
To: "trace-users@lists.onebuilding.org"<br>
<trace-users@lists.onebuilding.org><br>
Subject: [Trace-users] Air Flows (UNCLASSIFIED)<br>
Message-ID:<br>
<E777FD5A41D3B04A83296213737A85D70DC51048@EIS-MB0503CPC.eis.ds.usace.army.mil><br>
<br>
Content-Type: text/plain; charset="us-ascii"<br>
<br>
Classification: UNCLASSIFIED<br>
Caveats: NONE<br>
<br>
I use trane trace to get the loads. Then I select equipment, but I do not
use the cfms trace provides.<br>
<br>
Examples from trace:<br>
Stair well 7 cfm. (The unit I selected has only went down to 200 cfm)<br>
Storage room 12 cfm (I provided 50 cfm)<br>
And I round up other areas such as corridors and offices.<br>
<br>
The leed reviewer says the values in the model and in the design do not
match.<br>
<br>
Do I need to go back through my trace file and enter the air flows I used
in my design?<br>
The main system is an AHU with VAV boxes. If I go into each office and
enter the airflows to match the drawings, will the program use that airflow
at 100% or will the VAV box still modulate?<br>
<br>
Will I need to go through the pretend building and also manually change
the cfms to match the design? Or should I use the values trace spits out?<br>
<br>
Also, a comment was that the pumps (and air handling unit) in the model
did not match the model. I calculated that there would be 40 feet
of head in the system, but I selected (and scheduled) a pump that provides
a minimum of 60 feet of head. Do I need to enter in the scheduled values
or the values I calculated?<br>
<br>
<br>
<br>
Classification: UNCLASSIFIED<br>
Caveats: NONE</font></tt>
<br>
<br>
<br><tt><font size=2>Date: Wed, 30 Jul 2014 16:37:44 +0000<br>
From: "Eurek, John S NWO" <John.S.Eurek@usace.army.mil><br>
To: "trace-users@lists.onebuilding.org"<br>
<trace-users@lists.onebuilding.org><br>
Subject: [Trace-users] Outside air (UNCLASSIFIED)<br>
Message-ID:<br>
<E777FD5A41D3B04A83296213737A85D70DC561D3@EIS-MB0501WPC.eis.ds.usace.army.mil><br>
<br>
Content-Type: text/plain; charset="us-ascii"<br>
<br>
Classification: UNCLASSIFIED<br>
Caveats: NONE<br>
<br>
For Air Handling Units with VAV boxes Trace calculates the air flows based
on loads and outside air requirements.<br>
<br>
I haven't looked into the program code, but I have noticed that changing
interior loads changes the amount of outside air in the system.<br>
<br>
This makes sense to me since, if the AHU is operating at 30% outside air
and a room needs more air for cooling, the total amount of outside air
for the building would change.<br>
<br>
When I model the pretend building, it has different insulation, causing
different energy demands, causing different air flows, causing different
outside air values.<br>
<br>
How do I get the two outside air values to match?<br>
<br>
[On a side note, the outside air values shown on the report give the worst
case outside airflow, it wouldn't mean that the baseline and pretend buildings
will have identical outside air flows for the total 8760.]<br>
<br>
Do I go into the pretend building model and manual enter the outside air
cfm for each room to make it match the proposed building?<br>
<br>
John Eurek<br>
<br>
<br>
Classification: UNCLASSIFIED<br>
Caveats: NONE</font></tt>