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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Interesting! First, Sunayana, are you sure you should be using
<i>2013</i> App G/PRM? Even if the local energy code specifies ASHRAE 2013, LEED v4 uses ASHRAE 90.1-2010. And if utility programs are involved, there is usually some restriction on fuel switching. But that’s just bureaucratic detail.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">For the purposes of actually determining operating costs of
<i>realistic</i> alternative systems, it’s not clear the standard (or most BEM software) is addressing this adequately. In larger multi-unit buildings, it is probably
<i>not</i> practical to duplicate your proposed electric DHW system (in-unit, tank or instant), using gas, because all these heaters would require multiple flues, etc. So a REAL alternative is a central DHW heater with recirculation. That recirculation typically
has considerable loop losses, which the PRM <i>seems</i> to have directed us to ignore. However if you read the text carefully, this restriction (G3.1.3.6) targets circulating fluids used for space conditioning.
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-indent:.5in"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">(“G3.1.3.6 Piping Losses (<i>Systems 1, 5, 7, 8, and 11</i>). Piping losses shall not be modeled in either the proposed or baseline
building designs for hot-water, chilled-water, or steam piping.”) <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">However, the DHW language seems ambiguous on this point. In any case, central DHW loop losses are sometimes close to the actual DHW use energy. So the real
cost penalty of gas vs. electric may not be as large as it appears from a simple ratio of utility cost/Btu. California’s T24 compliance software, though based on E+, has developed a much more rigorous approach to DHW calculations that at least considers piping
losses in multi-family residential applications, along with researched draw profiles. The program passes off the DHW energy calculations to CSE (California Simulation Engine) for multi-family residential DHW. Perhaps more accessible, a recent paper “Strategy
Guideline: Proper Water Heater Selection” (<a href="http://www.nrel.gov/docs/fy15osti/63880.pdf">http://www.nrel.gov/docs/fy15osti/63880.pdf</a>) includes a broken link to
</span><span style="font-size:11.5pt">MultiFamily_Central_DHW_EvaluationTool_v1.0.xlsx.
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">You might try contacting the authors or Bldg America to see if you could get a copy. Output illustrated in the report is pasted below.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">If the project really can’t take the energy cost penalty caused by electric vs. gas DHW, and if the space heating uses HW boilers, there are systems that combine
the DHW and HW piping; essentially the HW coils are supplied with potable water. This reduces the cost of piping and boilers in the building compared with separate DHW and HW. It does seem to penalize the efficiency of the heating side a bit, as the “HW” return
temperature is often not as low as it would be for HW only. <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">A related item for all to consider is that new gas tank type condensing DHW heaters are being rated at efficiencies of up to 99%. However, this is at a test
condition which is rarely duplicated in reality (large flows of 60F inlet water). In any recirculating DHW system, the inlet T is usually much warmer, and in other cases, the draws are smaller and intermittent. Particularly the former reduces efficiency. That
effect is considered in eQ and E+ models of HEATING condensing boilers, but not in the eQ DHW heater representation. So just plopping 1.01 into the “HIR” field of an eQ DHW heater is not realistic. (I’m not sure if E+ could be set up to represent this correctly
or not.)<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I think there is some fodder here for LEED CIRs, ASHRAE Interpretations, proposed changes to the PRM, or direct questions to a code official or utility program
manager. In addition to the never-ending battle to have simulation software that provides reasonable representations of building components and operation!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Good Luck,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Fred<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">Fred Porter, BEMP, LEED</span></b><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">©</span></b><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:black">
AP<o:p></o:p></span></b></p>
<p class="MsoNormal" style="margin-bottom:2.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#7F7F7F">Principal Engineer<o:p></o:p></span></p>
<p class="MsoNormal" style="margin-bottom:2.0pt"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#7F7F7F">Sustainability Services<o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#005DAA">NORESCO<o:p></o:p></span></b></p>
<p class="MsoNormal"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif";color:#807F83"><a href="http://www.noresco.com/"><span style="color:blue">www.noresco.com</span></a></span><span style="font-size:9.0pt;font-family:"Calibri","sans-serif";color:#807F83"><o:p></o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:8.0pt;font-family:"Calibri","sans-serif";color:#7F7F7F"><o:p> </o:p></span></b></p>
<p class="MsoNormal"><img border="0" width="770" height="233" id="Picture_x0020_1" src="cid:image002.jpg@01D2521D.BA6D4C20"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> Bldg-sim [mailto:bldg-sim-bounces@lists.onebuilding.org]
<b>On Behalf Of </b>Sunayana Jain via Bldg-sim<br>
<b>Sent:</b> Friday, December 09, 2016 10:36 AM<br>
<b>To:</b> Angelica Walsh via Bldg-sim<br>
<b>Subject:</b> [External] [Bldg-sim] Multi-Family DHW<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">All,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">We are working on an energy model of a high-rise multi-family building in the New Jersey climate zone. This project will be using high efficiency in-unit electric water heaters
(0.95 EF) for DHW requirements.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">As per the latest code (ASHRAE 90.1-2013 Appendix G), baseline DHW system for a multi-family building has to be a gas storage water heater. As I understand, there will be a significant
energy cost penalty for using electric fuel versus natural gas in the design for DHW.<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Has anyone encountered similar situation?<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thanks,<o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="color:#17109C">Sunayana Jain CEM, LEED AP BD+C<br>
Sustainable Buildings & Operations Project Manager </span></b><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="color:#4F6228">Sustainable Solutions Corporation</span></b><o:p></o:p></p>
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