[Greenbuilding] The role of PV in achieving NZE

Wed Jan 26 16:45:49 CST 2011

Yes, oops, huge deal, 15 is purchased in PH (but you can't count PV) not including solar and interior gains. However it is not based on the same floor area. The basement is only counted as 60 per cent, the tank area and all walls are subtracted as are stairwells and such. 
So for the riverdale house I would estimate PH would consider it not 234 but more like 150 so the heating demand would not be 33.7 but more like 50 plus. Hence with normal solar and internal gains it would be well over 15. 
It occurs to me you could game the PH system and use solar hotwater to provide a good chunk of heat (like you do) rather than a PV run GSHP (which you can't count) and so you might actually make it under 15. For those NZE homes that don't use Solar water for space heat my previous analysis holds. 

PS are there publically available reports recording actual performance of the house yet?

Sent from my BlackBerry®

-----Original Message-----
From: Gordon Howell -- Howell Mayhew Engineering <ghowell at hme.ca>
Sender: greenbuilding-bounces at lists.bioenergylists.org
Date: Wed, 26 Jan 2011 14:53:10 
To: <greenbuilding at lists.bioenergylists.org>
Reply-To: Green Building <greenbuilding at lists.bioenergylists.org>
Subject: [Greenbuilding] The role of PV in achieving NZE

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

_______________________________________________
Greenbuilding mailing list
to Send a Message to the list, use the email address
Greenbuilding at bioenergylists.org

to UNSUBSCRIBE or Change your List Settings use the web page
http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org