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<body class='hmmessage'><div dir='ltr'>Hi,<div><br></div><div>I've created a detailed multi-zone model of a low energy home in Canada in EnergyPlus. I am looking at the peak heating load results and finding that the infiltration predicted seems quite high. I'd be interested to hear how other building modellers are approaching infiltration, and any general thoughts anyone has on this situation.</div><div><br></div><div>The model is based on the design - the house has not been constructed yet, but it is assumed that an ACH@50pa rating of 1 can be achieved. EnergyPlus has a simple infiltration modelling option, where the air leakage can be input as ACH@ regular pressure (I've assumed this is equal to 1/20 = 0.05).</div><div><br></div><div>EnergyPlus's basic infiltration model can adjust the infiltration rate for delta T and windspeed, using the following formula:</div><div><br></div><div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Infiltration = I_design * {A + B (T_zone - T_outdoor) + C*windspeed + D*windspeed^2 }<o:p></o:p></p></div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><o:p> </o:p></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">The big question I have is what coefficients should be used? EPlus provides three suggestions: </p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">1. coefficients from BLAST:</p></div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p></div><div style="font-family: Helvetica; font-size: medium; "><div><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">A = 0.606, !- Constant Term Coefficient<o:p></o:p></p></div><div><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">B = 0.03636, !- Temperature Term Coefficient<o:p></o:p></p></div><div><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">C = 0.1177, !- Velocity Term Coefficient<o:p></o:p></p></div><div><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">D = 0; !- Velocity Squared Term Coefficient</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">2. coeffs from DOE: 0, 0, 0.224 (windpeed), 0</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">3.Default: 1,0,0,0 which means a constant ACH with no modification.</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">The BLAST coefficients seemed to be the best to me because I think wind and temperature difference should be accounted for and there should always be some basic infiltration. However, using these coefficients at the peak heating load condition (delta T ~ 40C, windpeed = 27 km/hr) the infiltration rate is tripled from the base 0.05 ACH, and the total load from infiltration equals 2.2 kW, which is the largest component of the heating load.</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">For a relatively tight house this seems like an unrealistic value to me, but I do not have much to compare it against.</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Thanks,</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Hayes</p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><br></p><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">Hayes Zirnhelt, M.A.Sc<o:p></o:p></p></div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">EcoOptimal Building Energy Analysis<o:p></o:p></p></div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><a href="mailto:hayes@eco-optimal.ca" style="color: blue; text-decoration: underline; ">hayes@eco-optimal.ca</a><o:p></o:p></p></div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; "><a href="http://www.eco-optimal.ca/" style="color: blue; text-decoration: underline; ">www.eco-optimal.ca</a><o:p></o:p></p></div><div style="font-family: Helvetica; font-size: medium; "><p class="MsoNormal" style="margin-top: 0cm; margin-right: 0cm; margin-left: 0cm; margin-bottom: 0.0001pt; font-size: 12pt; font-family: 'Times New Roman', serif; ">T: 778.961.0086</p></div></p></div></div></div> </div></body>
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