Interesting post, John.<div><br></div><div>I'm afraid I need clarification on a few points.</div><div><br></div><div>If I understand correctly, in PH you can't increase the amount of total kWHs available by adding a solar PV array beyond the energy allotment specified by 120kWh/m2/yr. To me, this makes some sense because it avoids the examples of very inefficient houses compensating by installing enormous solar PV arrays.</div>
<div><br></div><div>But if one had an all-electric house and the exact amount of electricity allowed by the area formula (i.e. <span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12.8571px; border-collapse: collapse; ">120 kWh/m2/yr) were produced on-site using PV, wouldn't that that be more of a 1:1 source energy/site energy, and allow the full 120kWh/m2/yr? That would seem sensible. Or is PH not that sensible?</span></div>
<div><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12.8571px; border-collapse: collapse; "><br></span></div><div><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12.8571px; border-collapse: collapse; ">Hopefully I have expressed my question clearly. I look forward to a response.</span></div>
<div><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12.8571px; border-collapse: collapse; "><br></span></div><div><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12.8571px; border-collapse: collapse; ">Rob</span></div>
<div><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 12.8571px; border-collapse: collapse; "><br></span></div><div><br><div class="gmail_quote">On Sun, Jan 9, 2011 at 5:44 PM, John Straube <span dir="ltr"><<a href="mailto:jfstraube@gmail.com">jfstraube@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">No, Bob, PH is both smarter and dumber than that.<br>
The energy metric is based on source energy: that is energy that feeds an electric plant, or the gas used to transport and compress natural gas.<br>
So if you house was all electric, it would be limited to 42 kWh/m2/yr because the electricity grid in Germany requires 2.7 units of energy for every unit of electricity (this is 3.35 in the United States, but the PHIUS uses the ratio for the German power grid: no I am not making this up).<br>
This is what PH uses, as does the Department of Energy.<br>
The other thing is that your 1500 square foot house, would not be 139 square meters, as you need to subtract walls and stairwells and a few other things. So your house would become 105 or 110 m2. Yeah, I know, odd.<br>
Net effect is you would be allowed to use 4000-4500 kWh/yr if an all-electric house. This could be 2500 kWh/yr of electricity and 5000 kWh/yr of natural gas energy (170 therms). You can use passive solar and active heating or air/water, but not active generation of electricity.<br>
For a family of four, 2000 kWh of electricity and 170 therms of gas is no mean feat.<br>
<br>
The easy way to meet the 120 kWh/m2/yr source energy is to build a larger house. If you house was say 4000 sq ft (about 3000 sq ft measured by PH) you could use 6000 kWh of electricity and 680 therm of gas, which is about half (50%) the energy the average current house uses in the US, and about 30% less than a new code built home of your size.<br>
<div><div></div><div class="h5"><br>
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<br>
On 2011-01-09, at 5:47 PM, Bob Waldrop wrote:<br>
<br>
> ----- Original Message ----- From: John Straube<br>
> >area based energy metric (120 kWh/m2/yr)<br>
><br>
> This is the standard for the passive haus? Hmmm, for a 1500 sq ft house (1500/10.76 = 139.4 sq meters, times 120 = 16,728 kwh/yr, we do better than that with our amateur redneck extreme green house.<br>
><br>
> Bob Waldrop, OKC<br>
><br>
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</div></div><div class="im">Dr John Straube, P.Eng.<br>
Associate Professor<br>
University of Waterloo<br>
Dept of Civil Eng. & School of Architecture<br>
<a href="http://www.buildingscience.com" target="_blank">www.buildingscience.com</a><br>
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