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Dear John,<br>
I have enjoyed your critiques of PH, your BS (that's Building
Science) Insight articles, your posts here on this forum, as well as
your presentations in SF (San Francisco) this past, oops, last year.
I agree with much of what you have to say, and agree that some some
changes could help make PH more assessable in NA (North America). <br>
I had dinner with Dr. Feist in December which was great and I
had a chance to clarify a few issues. <br>
I was recently elected to the Board of PHCA (Passive House
California) and have been a certified Passive House Consultant since
June, and my invitation to you, and perhaps Joe too to come and talk
to us on a 4th Sunday at Pyramid Brewery in Berkeley still stands.
We could changes meeting dates too to accommodate you.<br>
You have pickup up and understood some of the details better
than some who have been through the training. I have made some
clarifications below as needed.<br>
<br>
On 1/10/2011 7:44 AM, John Straube wrote:
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>As you may know, there are 3 numerical requirements of PH,
with a bunch of recommendations that vary with whom you speak to
(of which I dont think any are required) and what day you speak
to them.</div>
<div>1. 120 kWh/m2/yr of source energy</div>
</blockquote>
This is for your all of your energy at your building site. And using
the U.S. DOE average for source energy conversions need to be
entered replacing the E.U. #'s. And the appropriate #'s for Canada
should also be used.<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>2. 15 kWh/m2/yr of annual space heating demand</div>
</blockquote>
and 15 kWh/m2/yr for space cooling, this and heating are based on
site energy use (as opposed to source energy)<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>3. 0.6 ACH@50 air tightness</div>
</blockquote>
This is a multipoint pressure & depressurization test, and must
pass both, equivalent to our ASTM-E779<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>and you should have a mechanical ventilation system.</div>
</blockquote>
Correct, and wrongly assumed to have to be a balanced HRV or ERV, it
can be exhaust or supply only. If you install a balanced system you
can't have more than a 1Pa delta between rooms (this is a
requirement per Dr. Feist)<br>
<br>
To be Certified, you have to submit plans, pictures & other
documentation showing your project was built as it was modeled in
the PHPP. You have to test the mechanical system and have it
balanced to +/-10%<br>
<br>
A note on square meters, the EU m2 TFA (treated floor area) is a net
usable square footage, it does not include stairs, and is only a %
of other spaces. We typically use a gross exterior floor area, so
without making an an adjustment to the floor areas the #'s can be
off (I made this mistake 3 years ago, before I knew better).<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">You have to meet 120 kWh/m2/yr site energy regardless
of PV. </blockquote>
Correct, end of sentence<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">Sort of. In fact, the PHPP spreadsheet uses a factor
of 0.7 to when calculating the factor for PV: I assume this means
in an all electric house you could use up to 120/0.7= 170
kWh/m2/yr.</blockquote>
No, there is no adjustments to any of the numerical requirements for
PV generate electricity. There has been discussion about a small
house, cold climate, and retrofit modifications, but I am not clear
on if they are official yet and the exact details.<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite"> I do not know why PV is rated this way, since in a
grid interconnected system like PV, the best factor one would
think was possible is 1.0. Anyway, the problem is that the PHPP
software basically ignores the PV generated electricity in its
verification: you can add PV but it does not reduce the energy
accounted for in the 120 number.
<div><br>
</div>
<div>So yes, this limits the size of the PV array and would avoid
very large PV arrays on small houses. That is good. We can
still have largish PV arrays on large houses. </div>
<div>For a large house in Sonoma California, this results in an
absurdly bad house, even if it met the other two requirements of
PH. A 300 m2 house (say 4500 sf) could use 300*120=36000 kWh.
This is a large amount of energy which could be provided by a 28
kW PV array, and render the house net zero. This would meet
PH's 120 requirement. But it may not meet the 15 requirement for
space heating and has nothing to do with the airtightness.
Meeting 15 is easily possible in Sonoma (where heat pumps work
very well). The only hard part is getting 0.6. Of course, in
Sonoma, 0.6 is a pretty stupid measure, since the energy saved
going from 1 to 0.6 is truly trivial. But if you want PH.<br>
</div>
</blockquote>
My rough calculation based on actual output of PV in the SF Bay area
would say it's an 18kW PV system to get to net zero source energy.
Still honking large! Net Zero Site energy would be much smaller, and
net zero Time Dependent Value (California's modified source energy)
would be even smaller. Net Zero is not a trivial pursuit, especially
in large house.<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>
<div>
<div><br>
<div>Sensible economics would reduce the size of PV arrays
on most house, eg if it is cheaper to save energy in a
specific project than it is to produce it, a sensible
design would choose to save energy. This is one of the
requirements that the Building America research program
tries to convey: use the lowest cost means of saving
energy, and every home reaches a point where PV is more
economical than, for example, adding another 2" of foam to
a 12" thick layer under your slab (to pick a favourite
example).</div>
<div><br>
</div>
<div>Now lets look at a small house in a cold climate like
Minneapolis. Say a 1500 sf house plus a basement, which
would have a PH area of maybe 130 m2. Thus we can only
use 15600 kWh of energy of all types, which would be 5770
kWh for an all electric house using the PHPP US values.
This would be hard to do all electric! Also total space
heating demand would be limited to 1950 kWh (=66 therms)
regardless of how this heating demand is met. This is
really hard and kind of crazy to achieve in a cold climate
small house. Meeting this 15 number is what drives many
of the extreme and non-obvious decisions, not so much the
120 number. At least this the case in cold climates and
small houses.</div>
</div>
</div>
</div>
</blockquote>
I think this is why they have considered a cold climate adjustment
to the 15 kWh/m2/yr budget.<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>
<div>
<div>
<div><br>
</div>
<div>For example, I currently live in a medium size house
(1500 sf raised ranch with a fully finished basement) in a
coldish climate (7500 HDD F). I cannot meet the 15 kWh/m2
demand number for space heating, although I could likely
meet the 120 number, and could reduce the blower door
number from 1 ACH@50 to 0,6 ACH@50 by spending another
$5000 or so (I looked at this during the retrofi: the
payback for this option was in the order of 100 years, and
it was 4 times cheaper to use PV to generate the energy
saved than saving it this way). But I could not get
certification if I wanted to because I dont meet the 15
number: I am over twice this with R45 walls, R80 ceiling,
R30 basement walls, triple glazed R6.5 windows, etc.
There is zero benefit to me, society or the environment,
to meet that 15 target but it is required for PH. For a
townhouse in a 5000 HDD F climate in, say Frankfurt
Germany, 15 would be a nice guideline (oh, I guess that is
where PH was developed..) but it still would not matter to
the goals of good buildings like the 120 number does. Oh,
and I heat primarily with wood from my own property, so
the fact that I use more energy for heating is pretty
irrelevant.</div>
</div>
</div>
</div>
</blockquote>
My congratulations to you if you are under the 120 kWh/m2/yr total
source energy budget (without PV) even if you don't meet the 15
kWh/m2/yr heating budget.<br>
<br>
You have achieved an equivalent level of performance, an energy
efficient house, and that's is what we all should be trying to
achieve, no mater what we call it!<br>
<blockquote
cite="mid:2B11A30D-DE7A-40AA-A1D6-C88D4668F48A@civmail.uwaterloo.ca"
type="cite">
<div>
<div>
<div>
<div><br>
</div>
<div>Just some more thoughts.</div>
<div><br>
<div>
<div>On 2011-01-09, at 9:08 PM, Rob Dickinson wrote:</div>
<br class="Apple-interchange-newline">
<blockquote type="cite">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
moz-do-not-send="true"
href="mailto:jfstraube@gmail.com">jfstraube@gmail.com</a>></span>
wrote:<br>
</div>
<br>
<br clear="all">
<br>
-- <br>
"I still find each day too short for all the
thoughts I want to think, all the walks I want to
take, all the books I want to read, and all the
friends I want to see." — John Burroughs (1837-1921)
American naturalist, writer<br>
<br>
</div>
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<div style="font-size: 14px;">Dr John Straube,
P.Eng.</div>
<div style="font-size: 14px;">Associate Professor</div>
<div style="font-size: 14px;">University of Waterloo</div>
<div style="font-size: 14px;">Dept of Civil Eng.
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