<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:arial,helvetica,sans-serif;font-size:10pt"><div>Hi Jen,<br>I agree. That does sound fishy. Generally, I do not use the DCV control feature within Trace to calc my energy savings from DCV. Some LEED reviewers have questioned using it as well. It's not that the algorithm is not correct its just that applying it to a real project can be tricky and require some level of judgment that the software doesn't know about. Similarly, I rarely use the ASHRAE 62 calc capabilities in Trace to simulate that calc. Except of the simplest of situations the calc can be thrown off very easily. One room can throw off the whole calc, so some judgment and adjustment is needed ....in my experience, it frequently take more time to comb through the calcs to figure out which spaces are throwing off the calc than to estimate the savings
via other means. I still estimate both with in Trace so it doesn't count as an exceptional calculation for LEED but I don't use Trace's built in routines to do it.<br><br>For DCV, based on the occupancy schedules for the spaces with DCV, I calc and make an adjusted OA schedule for those spaces. This is actually a lot less work and easier than it sounds.<br>Similarly, for the ASHRAE 62 calc, I do it on a spreadsheet and then force that cfm value at the system level in Trace (System level, Options Tab, Advanced options button). If you have a VAV system that needs an ASHRAE 62 calc and you are using DCV in some spaces, then you will need to adjust the system level OA schedule to reflect the DCV. <br><br>You can check to see that the program is bringing the correct OA cfm and adjust the schedule as needed by reviewing the cfms via the View Reports, Analysis tab, Graph Profiles and Energy button. Once there, In the view menu,
turn on the "settings" menu and switch to the "table" view. Then you can navigate the settings on the left side of the screen to get Trace to display the cfms of the AHU/system(s) in question. (You could also use this viewing feature to review what Trace did with the OA cfm when you used the automatic DCV and/or ASHRAE 62 calc within Trace to help find clues as to what's going on and if indeed Trace is simulating those features and the OA cfm correctly). <br><br>Again, the manual adjusted schedules and forced cfm method may sound difficult and like a lot of work, but it's not really. Once you do it once, you're done. And, it gives you a confidence level that Trace is simulating the OA cfm correctly. <br><br>Hope that helps.<br>Julia<br></div><div style="font-family: arial,helvetica,sans-serif; font-size: 10pt;"><br><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma"
size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> Jen Redington <redington@vitetta.com><br><b><span style="font-weight: bold;">To:</span></b> trace-users@lists.onebuilding.org<br><b><span style="font-weight: bold;">Sent:</span></b> Mon, August 30, 2010 8:15:32 AM<br><b><span style="font-weight: bold;">Subject:</span></b> [Trace-users] Demand Controlled Ventilation<br></font><br> <style> <!-- p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in;margin-bottom:.0001pt;font-size:10.0pt;font-family:Arial;} a:link, span.MsoHyperlink {color:blue;text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {color:purple;text-decoration:underline;} span.EmailStyle17 {font-family:Arial;color:black;font-weight:normal;font-style:normal;text-decoration:none none;} _filtered {margin:1.0in 1.25in 1.0in 1.25in;} div.Section1 {} --> </style> <div class="Section1"> <p class="MsoNormal"><font color="black" face="Arial"
size="2"><span style="font-size: 10pt; color: black;">I am doing an energy model for LEED and added demand controlled ventilation to several spaces in both the design and baseline models. This doubled my energy cost savings for the project. The space heating gas use went down 25% in the design model but doubled in the baseline model. I can’t see any reason why the baseline energy use would increase, and the savings in the design case seem a little unrealistic since DCV is only being used in some spaces. Any ideas what could be wrong? Any one else have any similar issues?</span></font></p> <p class="MsoNormal"><font color="black" face="Arial" size="2"><span style="font-size: 10pt; color: black;"> </span></font></p> <p class="MsoNormal"><font color="black" face="Arial" size="2"><span style="font-size: 10pt; color: black;">Thanks,</span></font></p> <p class="MsoNormal"><font color="black" face="Arial" size="2"><span
style="font-size: 10pt; color: black;"> </span></font></p> <p class="MsoNormal"><font color="black" face="Arial" size="2"><span style="font-size: 10pt; color: black;">Jen Redington</span></font></p> <p class="MsoNormal"><font face="Arial" size="2"> </font></p> </div> </div></div> </div></body></html>