[Greenbuilding] The role of PV in achieving NZE

Wed Jan 26 15:53:10 CST 2011

Hello John:

a) Thanks for your comments.  I am appreciating the GBL list and the 
people expressing their expertise.  I wasn't wanting to be 
obstructing... but I felt that Ross used a few hot words that I 
suggest needed to be challenged.  That's why I addressed my comments 
to him directly, rather than comment on the expertise of people on 
the list generally.  I apologise for being derogatory.  I should have 
been clearer.

b) Re the Riverdale NZE house energy consumption, as viewed on page 7 
of its profile 
<http://www.riverdalenetzero.ca/Riverdale_NetZero_house_--_project_profile.pdf> 
.
    ----- May I suggest that it is important to clarify what the term 
"energy use" means.  The PassivHaus standard is NOT 15 kWh/year/m2 of 
space heating, but rather it is 15 kWh/year/m2 of net energy 
consumption for space heating from the grid (if I am understanding 
correctly) -- a biiiiig difference.  The PassivHaus net energy 
consumption is net of its internal gains and passive solar gains 
(please provide any correction on this).
    ----- The RNZ house uses 33 kWh/year/m2 of space heating -- this 
is how much energy passes out through the house envelope regardless 
of where the energy is source.  The RNZ space heating is provided by 
a number of factors, as shown on the profile:  this includes internal 
electricity gains, internal people gains and passive solar.  So the 
net space heating requirements for RNZ are: Space heating incl fans = 
33.65 kWh/m2 plus mechanical ventilation = 2.02 minus usable passive 
solar space heating = 6.88 (37% is useable) minus useable internal 
gains = 4.13 (25% is useable), minus active solar space heating = 
9.57 giving a net space heating requirement of 15.08 kWh/year/m2.
    ----- How would a PH house do this same type of accounting in 
order to achieve 15 kWh/year/m2?
    ----- So may I suggest that an apples and apples comparison be made.
    ----- I can't imagine a NZE house being rationally made without 
being at least really close to the PH standard.

c) I agree with you re the Kamloops DreamHome COP...  time will tell, 
I am sure.

I appreciate your viewpoints and challenge.

+Gordon

Date: Wed, 26 Jan 2011 13:58:23 -0500
>From: jfstraube <jfstraube at gmail.com>
>To: Gordon Howell -- Howell Mayhew Engineering <ghowell at hme.ca>
>Cc: Ross Elliott <relliott at homesol.ca>,
>         greenbuilding at lists.bioenergylists.org
>Subject: Re: [Greenbuilding] PassivHaus and NZE comparison
>
>Sheesh Gordon, not sure what you meant by the "the company of facts 
>and knowledge" but I would say there is quite a bit of that on this 
>list.  Sounds kind of derogatory, and yet Ross is one of the "good 
>guys" (eg he is willing to have a rational conversation) and I 
>basically said what you said.
>Most of the "facts" you provided are available to anyone surfing the 
>web and/or talking to CMHC folks.  All of them were built into my commentary.
>
>However, it is not true that NZE homes meet the PH standard.  That 
>is my point.
>I attach a table of 5 of the houses I compared recently at the 
>bottom of this message.
>According to CMHC, the Riverdale Duplex (eg one wall less than a 
>single family house to loose heat) uses 33 kWh/m2/yr.  This is over 
>twice the PH standard, eg no where near the target.  I think the 
>Riverdale house is a exemplary cold climate home, a real step 
>forward.  And that is my point: you met the 0.5, but not the 15 
>heating target and yet use less energy than a PH by about 120 
>kWh/m2/yr. The Ottawa ecoHome fails the 0.6 test and the 15 test, 
>and the GreenDream meets the 7 and fails the 0.6.  (Note the 
>Kamloops gets this low by using a ground source heat pump and using 
>a COP = 5.1, which is crazy, and reality will certainly be closer to COP=3.5).
>The 120 primary target is an arbitrary but sensible target. By beef 
>is the 15 and 0.6 numbers, and the lack of climate response and 
>renewable energy sources.
>
>
>                   Avalon    Riverdale ecohome GreenDream Now
>Location            Red Deer  Edmonton  Ottawa  Kamploops  Toronto
>HDD (18C)               5500    5600    4600    3650    4000
>Floor Area (heated m2) 240      234     310     284     139
>Total Site Energy (ekWh)13094   14391   20646   11031   13475
>Heat Energy (kWh/m2)    23.9    33.7    40.2    7       23.1
>Roof (R)                87      100     60      60      36
>Wall                    70      56      44      44      40
>Window          5       7.3/10  5.7     4.5     5.7
>Basement walls  none    54      40      44      25
>Slab                    60      24      15      20      25
>ACH at 50          0.5     0.5     0.65    0.68    2.6
>PV Installed (kWp)      8.6     5.6     6.2     6.8     2.7
>SHW produced (kWh)      3886    1907    6665    2099    1824
>PV produced (kWh/yr)    9569    6224    8184    9963    2800