If your going to use the coefficient method you shouldn't use 1/20th of the ACH50 as the base infiltration. It is supposed to be an average value for typical exposure etc. You could use the BLAST eqn but you will need to adjust the inputs. I'd suggest looking at the pressure drop across the house at the peak wind condition and see what the Pa difference is across the windward and leeward walls. Assume a linear drop with pressure from your ACH50 value and pull out the "basic infiltration" from that.<div>
<br></div><div>I agree that 1ACH@50Pa is challenging with standard practice construction. The average new home in NZ without anything special is about 6ACH@50Pa. That said, two weeks ago, I witnessed a blower door test of a passive house (1st time builder) that was less than 0.3ACH@50Pa the first time we turned on the blower door. This was the first time this builder had attempted an "airtight" house - after fixing a few oversights it was at 0.26ACH@50Pa. The structure was designed to be sealed properly and he used ProClima's tapes and membranes. If you build a SIP house it is also likely to be under 1ACH50 without trying too hard. <br>
<div><br></div><div><br><div><div>Jason Quinn<br>+64 21 1846 911<br></div>
<br><br><div class="gmail_quote">On Tue, May 28, 2013 at 8:00 AM, <span dir="ltr"><<a href="mailto:bldg-sim-request@lists.onebuilding.org" target="_blank">bldg-sim-request@lists.onebuilding.org</a>></span> wrote:<br>
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<br>Today's Topics:<br>
<br>
1. Modelling Infiltration for Low Energy Houses (Hayes Zirnhelt)<br>
2. Re: Modelling Infiltration for Low Energy Houses (Shaun Martin)<br>
<br><br>---------- Forwarded message ----------<br>From: Hayes Zirnhelt <<a href="mailto:hzirnhelt@hotmail.com">hzirnhelt@hotmail.com</a>><br>To: "<a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a>" <<a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a>><br>
Cc: <br>Date: Mon, 27 May 2013 09:40:13 -0700<br>Subject: [Bldg-sim] Modelling Infiltration for Low Energy Houses<br>
<div><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 }<u></u><u></u></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"><u></u> <u></u></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<u></u><u></u></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<u></u><u></u></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<u></u><u></u></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">
</p><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, <a href="http://M.A.Sc" target="_blank">M.A.Sc</a><u></u><u></u></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<u></u><u></u></p>
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</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></p></div></div></div> </div></div>
<br><br>---------- Forwarded message ----------<br>From: "Shaun Martin" <<a href="mailto:smartin@shaunmartinconsulting.com">smartin@shaunmartinconsulting.com</a>><br>To: "'Hayes Zirnhelt'" <<a href="mailto:hzirnhelt@hotmail.com">hzirnhelt@hotmail.com</a>>, <<a href="mailto:bldg-sim@lists.onebuilding.org">bldg-sim@lists.onebuilding.org</a>><br>
Cc: <br>Date: Mon, 27 May 2013 11:39:03 -0700<br>Subject: Re: [Bldg-sim] Modelling Infiltration for Low Energy Houses<br><div lang="EN-CA" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Hi Hayes,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">The ZoneInfiltration:EffectiveLeakageArea approach in E+ might give you better results as it is tailored for residential buildings. It accounts for stack, wind and sheltering better than the ZoneInfiltration:DesignFlowRate method, which is used more for larger building models. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Regardless of the method, the bigger problem is the infiltration schedule. You could start with the schedules they have in eQuest. The operation of the HRV will affect the infiltration schedule. And, on larger buildings, of course, infiltration in core zones can be set to zero.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">On a 600m3 house, ACH50 = 1.0 is roughly 166 L/s. This is about 55 L/s at 10Pa, and translates to an effective leakage area of about 0.45 cm/m2. These are what I would use as design numbers. From experience, ACH50 = 1.0 (even 1.5) is a challenging target to reach and can’t be reached unless you use a blower door during construction. <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Hope this helps,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d">Shaun<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"> <u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><div><div style="border:none;border-top:solid #b5c4df 1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> <a href="mailto:bldg-sim-bounces@lists.onebuilding.org" target="_blank">bldg-sim-bounces@lists.onebuilding.org</a> [mailto:<a href="mailto:bldg-sim-bounces@lists.onebuilding.org" target="_blank">bldg-sim-bounces@lists.onebuilding.org</a>] <b>On Behalf Of </b>Hayes Zirnhelt<br>
<b>Sent:</b> Monday, May 27, 2013 9:40 AM<br><b>To:</b> <a href="mailto:bldg-sim@lists.onebuilding.org" target="_blank">bldg-sim@lists.onebuilding.org</a><br><b>Subject:</b> [Bldg-sim] Modelling Infiltration for Low Energy Houses<u></u><u></u></span></p>
</div></div><p class="MsoNormal"><u></u> <u></u></p><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif"">Hi,<u></u><u></u></span></p><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif""><u></u> <u></u></span></p>
</div><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif"">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.<u></u><u></u></span></p>
</div><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif""><u></u> <u></u></span></p></div><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif"">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).<u></u><u></u></span></p>
</div><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif""><u></u> <u></u></span></p></div><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif"">EnergyPlus's basic infiltration model can adjust the infiltration rate for delta T and windspeed, using the following formula:<u></u><u></u></span></p>
</div><div><p class="MsoNormal"><span style="font-family:"Calibri","sans-serif""><u></u> <u></u></span></p></div><div><div><p class="MsoNormal">Infiltration = I_design * {A + B (T_zone - T_outdoor) + C*windspeed + D*windspeed^2 }<u></u><u></u></p>
</div><div><p class="MsoNormal"> <u></u><u></u></p><p class="MsoNormal">The big question I have is what coefficients should be used? EPlus provides three suggestions: <u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">1. coefficients from BLAST:<u></u><u></u></p></div><div><p class="MsoNormal"><u></u> <u></u></p></div><div><div><p class="MsoNormal">A = 0.606, !- Constant Term Coefficient<u></u><u></u></p>
</div><div><p class="MsoNormal">B = 0.03636, !- Temperature Term Coefficient<u></u><u></u></p></div><div><p class="MsoNormal">C = 0.1177, !- Velocity Term Coefficient<u></u><u></u></p>
</div><div><p class="MsoNormal">D = 0; !- Velocity Squared Term Coefficient<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">2. coeffs from DOE: 0, 0, 0.224 (windpeed), 0<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">3.Default: 1,0,0,0 which means a constant ACH with no modification.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">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.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">For a relatively tight house this seems like an unrealistic value to me, but I do not have much to compare it against.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Thanks,<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Hayes<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><div><p class="MsoNormal">
Hayes Zirnhelt, <a href="http://M.A.Sc" target="_blank">M.A.Sc</a><u></u><u></u></p></div><div><p class="MsoNormal">EcoOptimal Building Energy Analysis<u></u><u></u></p></div><div><p class="MsoNormal"><a href="mailto:hayes@eco-optimal.ca" target="_blank">hayes@eco-optimal.ca</a><u></u><u></u></p>
</div><div><p class="MsoNormal"><a href="http://www.eco-optimal.ca/" target="_blank">www.eco-optimal.ca</a><u></u><u></u></p></div><div><p class="MsoNormal">T: 778.961.0086<u></u><u></u></p></div></div></div></div></div></div>
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