Solar hot water

[George]

OK boys and girls, I'm confused about solar hot water (SHW) vs solar
electricity (PV) in regards to PHPP calculation (2007 PHPP version
05-05-09)

My question: Why does SHW reduce PE Value but PV does not reduce PE
Value? Is PH philosophically opposed to one form of on site solar
generation vs another? Details:

SolarDHW tab
line 12 solar collector area, if I change it from zero (no SHW) to 24
ft2 (a 30-tube vacuum array), then line 24 solar contribution to
useful heat changes from 0 to about 4000 kBTU/year. So far so good.

PE Value tab
line 15 DWH Production, the above SHW change results in a change here
from 6.2 to 3.2 kBTU/ft2/year for this 1369 ft2 TFA house. That means
line 96 Total PE Value changes from 44.1 to 36.6 kBTU/ft2/year, which
means this house would not certify as PH (exceeds 38.0 for PE) without
the SHW array.

PE Value tab
line 107 Planned Annual Electricity Generation, if I change from zero
(no PV) to 3000 kWh/year (a 3 kW array), line 110 Conservation by
Solar Electricity changes from zero to 15 kBTU/ft2/year, as it
should. But line 96 Total PE Value does not change.

So I can reduce PE Value with SHW but not with PV. What is with that?


George Ostrow
VELOCIPEDE architects inc

[Martha Rose]

My understanding is that they don't want the PV to let you off the hook of good energy efficient design. In Passive House eyes, the PV is to get you to either true net-zero or positive-zero.

 

Anyone else want to add to this?

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[David Posada]

I don't recall any specific explanation for this.

 

I can see George's point that you could build two versions of the same house - one with PV, one with SHW - and the SHW would be a PH and the PV one would not, even with a non-grid tied system. I'm sure we could find other examples of distinctions like this that seem arbitrary - seems like they are inevitable anytime you have codes, standards, or rating systems.

 

I can imagine one rationale, though:  

Solar hot water systems convert  solar energy into a form that can most practically be used on site, and used fairly immediately, so it is more consistent with the notion of "passive," site-specific, low-energy strategies, whereas PV produces a form of energy that is easily transferred to the grid.

 

One's demand for hot water is also typically less than one's demand for electricity,  so you're less likely to "get off the hook" as Martha says with a big SHW system as you might with an big PV system.  

 

You might also draw an analogy to a local barter-based currency vs. converting everything into dollars...

 

That's my impression of the possible reasoning.

 

David Posada

GBD Architects

[Hayden Robinson]

I’ve never dealt with this issue myself. But I’ve overheard similar conversations before, and my (only partially informed) understanding is the same as Martha’s.

 

Hayden Robinson Principal

hayden robinson architect

206.691.3445

www.haydenrobinson.com

 

From: passive...@googlegroups.com [mailto:passive...@googlegroups.com] On Behalf Of Martha Rose
Sent: Wednesday, December 15, 2010 12:54 PM
To: passive...@googlegroups.com
Subject: Re: Solar hot water

 

My understanding is that they don't want the PV to let you off the hook of good energy efficient design. In Passive House eyes, the PV is to get you to either true net-zero or positive-zero.

[Rob Harrison AIA]

On Dec 15, 2010, at 12:28 PM, George wrote:

So I can reduce PE Value with SHW but not with PV.  What is with that?

If you could count PV toward the specific heat limit, and/or primary energy limit, then almost any building could be certified as a PH if it fit the air-tightness criterion. Take a building that conserves say 50% more energy than typical, add enough PV and you could make that happen. I think Dr. Feist's intention was to make Passive House first about the building envelope and design, rather than just slapping expensive technology onto a mediocre building. 

~Rob

 

Rob Harrison AIA :: Certified Passive House™ Consultant

HARRISON architects

1402 Third Avenue  Suite 515

Seattle, WA  98101-2120

206.956.0883

http://twitter.com/#!/robharrisonAIA

http://harrisonarchitects.com/

lyrical sustainable design

[George]

Thanks for all the feedback, though it was mostly speculation as to the rationale, and still leaves me unsatisfied.  I think I will post this question to PHIUS and check the blogs to see if there is an official PH position on this issue.

As for "getting off the hook," a couple thoughts:

1. domestic water heating has nothing to do with building envelope/space heat demand, just with PE.
2. every PH still has to achieve 4.75 kBTU/ft2/year maximum space heating demand, in addition to PE criterion and airtight criterion, so unlimited PV or SHW will not make a mediocre house a PH all by itself.
3. if the house is radiant heated or otherwise uses solar heated water to provide space heat and not just domestic hot water then it could slap on a massive SHW array to artificially reduce the PE value for space heat (boiler covered fraction could be 100%) and DHW which would then allow inefficient appliances/lighting.

Presuming one is not trying to game the system by compensating for inefficient design with excessive PV or SHW, it seems somewhat arbitrary to me to allow SHW but not PV.  All houses are likely to require at least some electricity and hot water, so who cares which device you use to harness the sun to provide those energy needs on site?  The issue for both is seasonal sizing and storage, especially in Seattle's climate, as well as high first cost.  I feel that homeowners and their designers should have flexibility with system choice without a PH penalty.

[Sam Hagerman]

According to Katrin, in a conversation I had with her about this very issue, Rob is exactly right. 

The intent is to discourage "crappy" buildings made PH compliant by being air tight and having large PV installations.

Further evidence of the value optimization at the core of the PH apple.  Like a few other important base concepts it is not overtly articulated but rather tacit and only evident by observation of initially confusing results.

You still get the slight benefit of .7 value factor, no?  PHPP Planning Package 2007, p. 166.

Thank goodness for the community/hive-mind!

Sam

For further muddy water:

http://www.passivehouse.us/bulletinBoard/viewtopic.php?f=12&t=99

http://www.passivehouse.org.nz/forum/viewtopic.php?id=39&p=1

These links are thanks to Skylar but definitely look at the second one where Graham Irwin wrestled this out, ad infinitum, with the NZ folks about a year ago.  While there was no clear "bright-line" answer, the discussion is fascinating. 

In my humble opinion it further emphasizes the "optimization" that should be the engine of PH.  To save the world we need to work together to remove the "luxury" price tag from the passive house construction.

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[George]

Sam,

Thanks for the direct reference from Katrin Klingenberg, which is
tantamount to policy. I disagree that crappy buildings with large PV
systems are bad whereas crappy buildings with large SHW systems are
good, but if I want a PH certification I have to play by PH rules.

The link to the New Zealand discussion is yet another example of the
debate and confusion over CO2e impact at the point of use depending on
fuel choice. Months ago I suggested to Alex Wilson that EBN do a
feature article on this topic. I will prod him again.

As for 0.7 factor, I only have PHPP 2004 manual which ends at page
160, so I am not sure what you mean. On Electricity tab, if I change
cells AG7 and AI7 (Energy Carrier for Space Heating and DHW) from 2.7
(electricity mix) to 1.1 (natural gas) or 0.7 (electricity PV), there
is no change in PE Value tab cell E96 (Total PE Value). On PE Value
tab, if I change cells G26 or G38 from 2.7 to 1.1 or 0.7 similarly
there is no change in Total PE Value. Am I missing something obvious?

George Ostrow
VELOCIPEDE architects inc

On Dec 16, 7:50 pm, Sam Hagerman <s...@hammerandhand.com> wrote:
> According to Katrin, in a conversation I had with her about this very issue,

> Rob is *exactly* right.

>
> The intent is to discourage "crappy" buildings made PH compliant by being
> air tight and having large PV installations.
>
> Further evidence of the value optimization at the core of the PH apple.
> Like a few other important base concepts it is not overtly articulated but
> rather tacit and only evident by observation of initially confusing results.
>
> You still get the slight benefit of .7 value factor, no?  PHPP Planning
> Package 2007, p. 166.
>
> Thank goodness for the community/hive-mind!
>
> Sam
>
> For further muddy water:
>
> http://www.passivehouse.us/bulletinBoard/viewtopic.php?f=12&t=99
>
> http://www.passivehouse.org.nz/forum/viewtopic.php?id=39&p=1
>
> These links are thanks to Skylar but definitely look at the second one where
> Graham Irwin wrestled this out, ad infinitum, with the NZ folks about a year
> ago.  While there was no clear "bright-line" answer, the discussion is
> fascinating.
>
> In my humble opinion it further emphasizes the "optimization" that should be
> the engine of PH.  To save the world we need to work together to remove the
> "luxury" price tag from the passive house construction.
>
> On Wed, Dec 15, 2010 at 3:42 PM, Rob Harrison AIA <
>
>
>
> r...@harrisonarchitects.com> wrote:
> > On Dec 15, 2010, at 12:28 PM, George wrote:
>
> > So I can reduce PE Value with SHW but not with PV.  What is with that?
>

> > If you *could* count PV toward the specific heat limit, and/or primary

> > energy limit, then almost any building could be certified as a PH if it fit
> > the air-tightness criterion. Take a building that conserves say 50% more
> > energy than typical, add enough PV and you could make that happen. I think
> > Dr. Feist's intention was to make Passive House first about the building
> > envelope and design, rather than just slapping expensive technology onto a
> > mediocre building.
>
> > ~Rob
>
> >     Rob Harrison AIA :: Certified Passive House™ Consultant
> > HARRISON architects
>
> > 1402 Third Avenue  Suite 515
> > Seattle, WA  98101-2120
> > 206.956.0883

> >http://twitter.com/#!/robharrisonAIA<http://twitter.com/#%21/robharrisonAIA>
> > *http://harrisonarchitects.com/*

>
> > lyrical sustainable design
>
> >  --
> > You received this message because you are subscribed to the Google Groups
> > "Passive House Northwest" group.
> > To post to this group, send email to Passive...@googlegroups.com.
> > To unsubscribe from this group, send email to

> > PassiveHouseN...@googlegroups.com<PassiveHouseNW%2Bunsu...@googlegroups.com>
> > .

[graham]

This is my, by now, fairly well researched assumption:

1) A solar thermal system produces energy that is used to directly
offset energy consumption by the building in question. PV, in most
circumstances, produces power when the building least needs it (at
least in a heating climate.) As such, you cannot offset the source
(primary) energy requirement with PV generated electricity, unless you
can demonstrate that this power actually offsets consumption by the
building at the time the electricity is produced. Otherwise, it is a
carbon offset, which is exactly how PHPP treats it. If you can show
that the PV system offsets energy consumption at time of production,
you can use a PE factor of 0.7 for that portion of the site (final)
energy consumption, as opposed to the standard electricity PE factor
of 2.7. This can be a substantial reduction in the source energy use.

2) To echo some earlier comments, it is worth remembering that the
heating and cooling demand limits are not consumption limits, they are
inherent characteristics of the building itself. The rationale behind
this is that the building should last a very long time, so it should
have an inherent level of performance, regardless of what equipment is
installed in or on it at present.

Cheers,
Graham

> > > PassiveHouseN...@googlegroups.com<PassiveHouseNW%2Bunsubscribe@go oglegroups.com>

[Rob Harrison AIA]

Thank you Graham. Makes perfect sense. I knew there was a rational reason in there trying to get out. 

Rob

Rob Harrison AIA :: Certified Passive House™ Consultant

HARRISON architects

1402 Third Avenue  Suite 515

Seattle, WA  98101-2120

206.956.0883

http://twitter.com/#!/robharrisonAIA

http://harrisonarchitects.com/

lyrical sustainable design

To unsubscribe from this group, send email to PassiveHouseN...@googlegroups.com.

[James]

Okay, I admit that I have enjoyed this exchange gentlemen....you might
be a geek if....

On Dec 18, 11:04 pm, Rob Harrison AIA <r...@harrisonarchitects.com>
wrote:

> Thank you Graham. Makes perfect sense. I knew there was a rational reason in there trying to get out.
>
> Rob
>
> Rob Harrison AIA :: Certified Passive House™ Consultant
> HARRISON architects
>
> 1402 Third Avenue  Suite 515
> Seattle, WA  98101-2120

> 206.956.0883http://twitter.com/#!/robharrisonAIAhttp://harrisonarchitects.com/

[George]

OK, makes sense. Thanks for the lucid explanation. PH indeed has a
bias and it is understandable. We could then debate the merits of
energy offset local to a single building vs carbon offset for the
planet as a whole and so forth. But that is somewhat beyond the scope
of PH.

Still problematic with SHW in Seattle is the huge seasonal variation
with supply vs the relatively constant demand for heated water. So
like a broken clock that is right twice a day, a certain size SHW
system is balanced only twice a year, and the rest of the year it does
not produce energy that is used to directly offset energy
consumption. Until such time that renewables comprise more than a
tiny fraction of electricity generation, grid tied PV always offsets
fossil fuel use year round at the utility scale.

It is interesting to note that our PH meets the space heat demand
criterion (4.75) and has a best-of-class base load package (heat pump
water heater serving low flow fixtures, better than Energy Star
appliances, all CFL/LED lighting, and minimized plug loads). Yet if
fueled with electricity only, no natural gas, it cannot meet the PE
criterion (38). So need to either slap on an absurdly large SHW array
or bring in a gas meter to get PH certified, even though neither makes
practical sense for this project. Given the site location, gas simply
won't happen, so PH is "forcing" the addition of an oversized SHW
array.

I suppose the other way to reduce PE is to reduce space heat demand,
but it would be my assumption that if the 4.75 criterion is met,
enough has been done with the envelope. But perhaps not. Having not
done multiple PHs, I don't have a sense of how best to adjust this
one.

This house is 1369 ft2 TFA, intended for occupancy by 4 people (PHPP
assigns 3.6 people). So not an overly large single family house nor
overly capacious per person. The lesson here may be to assure natural
gas service or off the grid PV before attempting a PH. I don't know
the details of what the 4 already certified WA and OR PHs did for fuel
source (Bilyeu, Everhart, Whitmore, Giampietro). Time to find out.

George Ostrow
VELOCIPEDE architects inc

On Dec 18, 7:25 pm, graham <gra...@essentialhabitatconsulting.com>
wrote:

[Martha Rose]

George,

 

I say, don't sweat the brand label and do your best in a way that makes the most sense.

 

I know this statement is slanderous amoung this group, but let's be reasonable!

 

Spec builder logic,

 

Martha

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[Hayden Robinson]

Martha,

Thanks for your input. No statements should be considered slanderous in this discussion. We’re talking about technology, not religion or ideology. Any thoughtful idea should be welcomed. The best ones will rise to the top.

Hayden

 

Hayden Robinson Principal

hayden robinson architect

206.691.3445

www.haydenrobinson.com

 

From: passive...@googlegroups.com [mailto:passive...@googlegroups.com] On Behalf Of Martha Rose
Sent: Monday, December 20, 2010 9:42 AM
To: passive...@googlegroups.com
Subject: Re: Solar hot water

 

George,

[Martha Rose]

Thanks Hayden,

 

The idea of building plus zero is so cool and prestigious that of course we all want to go there. I say yes to all of the paths.

 

Martha

[Albert Rooks]

With Martha's highly rational comment in mind as an overall reality check…

The interesting "nerd" question is how much more in envelop improvements (below the already excellent 4.75) would it take to bring the the PE in line? And how would it compare in cost and sanity to the (quoting George) absurdly large SHW array? This is not the only time this situation will come up. Dan is in the east on vacation so it might be a few days b4 we find out what his DHW source is. There is no project page for his or Blakes on Linda Whaley Passive House Projects US page, so I guess we'll have to wait and hear from the "artists" themselves. Both projects are kinda urban so I'm betting there is "gas" involved.

Albert.

Albert Rooks

The Small Planet Workshop 

by WestCoast Associates Inc.

albert...@mac.com

Tel: (360) 951-1492

www.smallplanetworkshop.com

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[graham]

George,

I take exception with some of the conclusions you've drawn from this
discussion.

First, Passive House does not have a "bias" per-se, for solar thermal
over PV. Passive House is fundamentally intended to produce buildings
with very low source energy consumption (thereby low global warming
impact) in the most cost effective way possible. IM(H)O, it is rather
well configured in that regard. It is a "stubborn" standard, but that
is one of its essential strengths. It is also an impressive and
rigorous standard - if it weren't, why would anyone care (at least
without much more marketing!!!) If you want more flexible recognition,
options abound, and no one is requiring you to seek PH certification.
As I've explained, you can use PV to offset source energy (via a lower
PE factor) for the energy that is produced and used to directly offset
the building's energy consumption, you just don't get source energy
reduction for energy that flows into the grid.

Are far as net-metering goes, the concept of "net zero" is only
tangibly connected to reality in terms of the customer's utility bills
(and that arrangement is more determined by utility company policies
than environmental concerns) - beyond that it's really a carbon offset
scheme. There's absolutely nothing wrong with that (and PHPP
acknowledges the carbon reduction of a PV system) but one can also
offset carbon by building a home near public transit and/or work,
riding a bike, planting trees, eating vegetarian food, etc., etc. In
that realm, I don't think that PV is even close to the most cost
effective approach for carbon offset. See the McKinsey report for more
details: http://www.mckinsey.com/clientservice/sustainability/pdf/Impact_Financial_Crisis_Carbon_Economics_GHGcostcurveV2.1.pdf

The trouble is that utilities do not recognize that "a kWh saved is a
kWh earned" in terms of the cost structure, incentives for PV, etc.
This is a fundamental distortion of the market, and it has the effect
of encouraging a rather expensive, inefficient approach to carbon
reduction (PV) at the expense of a rather cheap, effective approach
(efficiency.) The situation is even more acute in Germany, where PV
produced electricity is purchased from the utility at a high rate, and
there is no limit on the amount one can receive (you can actually make
money on the PV system, not just zero your annual utility bill.)

Passive House was not intended to "save the world." It is cohesively
focused on producing buildings with very low global warming impact (a
GREAT HELP in saving the world, BTW) but it does not pretend to direct
human behavior in broader terms. As such, it is quite well focused,
objective, and fundamentally and rigorously based in science. I like
that very much, as I want help from PH designing great buildings. The
endless other questions in life I will reach my own conclusions on,
through various means of my choosing.

Anyhow, enough of my "sermon," as Hayden might argue. Back to physics:

The issue you are describing stems from the fact that grid supplied
electricity is quite "dirty" from a carbon emissions standpoint, so
consuming the same quantity of site energy of natural gas (for
example) compared to electricity is beneficial, since the total carbon
emissions are lower. That said, an all-electrical house is a laudable
IM(H)O goal for the long term, and often there is an impediment to
natural gas use that is project specific. Some day (I hope) we will
have a renewable energy grid with very efficient all-electric
buildings connected. That's the real answer IM(H)O. The clean grid's
in the works too, at some level, but we're here to talk about the
consumption side.

So, what to do? You hint at the solution in your latest email. The key
is to avoid jumping to conclusions about what is best, and use the
tools in a methodical manner to discover a quantified, cost optimized
solution. Some thoughts:

1) I would first look at the heating demand of the building. Yes, you
have reached a very low level by meeting the Passive House standard,
but how hard would it be to lower that, and how costly? This is
actually part of the PH design process (page 30 in my older PHPP
manual, a flowchart labeled "Input sequence (residential building)."
One optimizes the shell first, then the primary (source) energy, then
iterates back through the shell optimization is necessary. So, on to
the next step!!! ;-) Katrin built the Smith house as an all-electric
building with electric resistance heat and lowered the heating demand
to approximately 50% of the PH standard. All of my PH designs are
subjected to an exhaustive (exhausting???!!!) process of PHPP cost
optimization to be sure that I've picked all the low hanging fruit, PH
Standard #'s aside. You can buy a lot of insulation for the cost of PV
or solar thermal panels, and the shell represents a "permanent
payback" that pays back twice (once in energy not consumed, secondly
in renewables not required.) The concept that the heating demand of 15
kWh/m2.a is the cost optimal solution in all climates and in all
projects is one that needs to be verified, IM(H)O, outside of Central
Europe and perhaps in perpetuity. Even if that is the average point
for cost optimization, do you want to be on the high or low side of
the average when building your project?

In your email you speak of the difficulty and cost in providing space
heating with solar thermal - that stems from the fact that you're,
essentially, trying to use the sun to make up for the fact that
there's not much sun!!! ;-) It may very well be that the solar thermal
system would be pushed well beyond the point of diminishing returns
and cost effectiveness with the heating demand and backup system that
you've designed - it certainly is with conventional buildings. I dare
say it would be even worse for PV, if you were trying to provide the
heating energy at time of use that way. So, how do you make up for the
fact that the peak demand for heating comes at a time of low
insolation? 1) Move the building to somewhere with higher winter
insolation or, 2), lower the heating demand!

I would also scrutinize my mechanical system. You mention a heat pump
water heater. Where does this device obtain its heat? If it is from
within the shell, it is cooling the building more than it is heating
the water. You make no mention of the heating system, but I'm guessing
this is electric resistance by the difficulty you're having. Have you
looked at heat pumps? Perhaps a system that does hot water and space
heating using outdoor air? These systems have a similar curve to solar
thermal if you have foggy, cold winters, but it would help you
immensely.

That took WAY too much time, and there's no congenial beer drinking
afterwards!!! ;-)

Happy Holidays,
Graham

[George]

Thanks for the feedback. A couple responses:

1. PH is a wonderful program that will bring much more energy
efficient buildings to the world. It has certainly improved my design
practice in that way. I love PH, I just have a quibble with the way
they treat PV and SHW differently.

2. Net zero, like PH, is a succinct and appealing if somewhat
arbitrary target towards the overall goal of significantly reducing
energy use. So far there are 4 certified PH in WA and OR (that I know
of) and only 1 net zero house in WA and OR (that I know of) despite a
dozen attempts (that I know of). So net zero is not easy, and it
raises the bar in a good way. In theory you could add huge PV arrays
to offset wasteful consumption, but none of the net zero projects I
know of have taken that approach. They are all about demand
reduction, same as PH.

3. I consider all fossil fuels "dirty." You should see some of the
horrific photos of natural gas well fields that Jeremy Smithson
presented at Solar Washington meeting in Dec 2010. Sure, some fossils
have lower carbon count than others, but that only makes them
relatively better. And carbon content is just one piece of the fossil
fuel usage picture. Think (Persian) Gulf War or Gulf (of Mexico) Oil
Spill, for example.

4. The carbon content of electricity at the point of use, as opposed
to the point of generation, is in my time-limited research not really
known. Seattle City Light can claim carbon neutral generation, but
the computer I am using right now in Seattle is likely powered at
least in part by burned coal.

5. Some carbon offsets may be easier or less costly than others, but
in my opinion we need to do ALL of them NOW. By the time everybody
acknowledges that climate change is real, is human caused, and
requires a dramatic change in how we live on this planet, it is going
to be too late to reverse the damage.

6. For the Carnation PH, we improved the envelope a lot using PHPP as
a guide (overhang bigger by 6", R40 vs R38 in walls, etc.). Our
approach was envelope first, power plant second, appliances third, and
then renewable generation fourth. This house is struggling for four
reasons I can think of: 1) it is designed for 4 people (for resale,
ugh) but only 2 people will live in it, so it is physically bigger
than it really ought to be, 2) it is crawl space instead of slab on
grade, 3) it is one story instead of two story so its floor and
ceiling exposed to the atmosphere is double compared to the exposed
exterior wall, 4) it is all-electric. You do the best you can with
the owner's design brief and priorities.

7. For the Carnation PH, we went with an HRV (likely Zehnder) for most
of the space heating with a 2kW electric resistance booster heater
(the proverbial hair dryer). For water heating, we went with a heat
pump water heater (likely Rheem) located in the enclosed but not
insulated and not heated garage, so it is not sucking space heat to
warm water.

8. I am not a CPHC nor have I taken the course, so I could be missing
something, no doubt about it. But I got paid consulting on this
project from two CPHCs so I believe that what we are missing likely
comes from our collective relative inexperience with designing PH for
the Pacific Northwest, not from a lack of understanding of the
concepts or the minutae of the PHPP calcs.

9. I truly appreciate your input. I hope to present this house as a
case study at PH Seattle meeting and let others weigh in, too.

George Ostrow
VELOCIPEDE architects inc

On Dec 21, 11:58 am, graham <gra...@essentialhabitatconsulting.com>
wrote:

> details:http://www.mckinsey.com/clientservice/sustainability/pdf/Impact_Finan...

[George]

I got responses from the 4 certified PH in WA and OR about source fuel
mix, as follows:

Salem, Rue Evans PH (Bilyeu)
Is an all-electric house. Installed a 40 tube SHW which PHPP says
will provide 80% of annual water heating. Without the SHW, this house
just exceeds the 38 PE limit.

Portland, Everhart PH (Everhart)
Urban site with gas already connected to house. For the remodel to a
PH, disconnected the gas from the furnace and fireplace, now gas used
only for water heating, range, oven, and clothes dryer. No SHW,
though may add in the future.

Seattle, Courtald Place PH (Whitmore)
Wanted to do an all-electric house, ran into the PE limit when
applying the 2.7 multiplier, so connected to natural gas since an
urban site. Also used SHW to get under the PE limit.

Seattle, Mini B PH (Giampietro)
All electric house but with a 10 tube evacuated SHW array. PHPP says
it will provide 50% of annual water heating. Without the SHW, this
house would exceed the 38 PE limit.

I will also copy Bilyeu's comment about "oversized" SHW:
"I am aware of the myth that is perpetuated by the flat-panel
proponents that too much heat is generated in the summer, but it isn't
an issue in reality. We've been putting in evacuated systems for ~5
years now without any issues. The particular system that we use also
has overheat protection built into each tube, but worst case scenario
you would need to replace then glycol more frequently if you
continually overheated things -- nothing will overpressure or
explode...."


I am going to sign off on this thread for now. I have to get back to
paid work.

George Ostrow
VELOCIPEDE architects inc

On Dec 20, 6:24 pm, Albert Rooks <albert.ro...@mac.com> wrote:
> With Martha's highly rational comment in mind as an overall reality check…
>
> The interesting "nerd" question is how much more in envelop improvements (below the already excellent 4.75) would it take to bring the the PE in line? And how would it compare in cost and sanity to the (quoting George) absurdly large SHW array? This is not the only time this situation will come up. Dan is in the east on vacation so it might be a few days b4 we find out what his DHW source is. There is no project page for his or Blakes on Linda Whaley Passive House Projects US page, so I guess we'll have to wait and hear from the "artists" themselves. Both projects are kinda urban so I'm betting there is "gas" involved.
>
> Albert.
>
> Albert Rooks
> The Small Planet Workshop
> by WestCoast Associates Inc.

> albert.ro...@mac.com
> Tel: (360) 951-1492
>
> www.smallplanetworkshop.com

[Dan Whitmore]

Great discussion everyone. Here's my thoughts.

I suspect the most cost effective work-around for meeting the Primary
Energy requirement in an all-electric PH without needing massive Solar
Hot Water is what the Bileyu, Fairview and Smith Houses used: a heat
pump w/ a very good Coefficient Of Performance. I haven't installed
one yet and it seems counter-intuitive to use a mini-split with air
conditioning capacities around here, yet their efficiencies will
directly offset the 2.7 PE hit. When designing the heating system for
the Courtland PH and attempting all- electric, I worked with a heat-
pump water heater with heating coil in the ventilation system. I was
unable to find an affordable heater with good enough COPs.
(Integrating one heat source for two living units made mini-splits
akward/even more expensive.) I got fairly close and probably could
have achieved it, but the budget wouldn't allow the huge SHW array
necessary. Since gas is readily available in the neighborhood, I used
that as a fall-back. With gas I was able to eliminate the need for a
SHW array but still achieve a PE of 37 kBTU/ft2 yr.

For me this is an acceptable compromise, especially since the
mechanical system is shorter-lived than the structure. I hope the
expensive condensing gas water heater (AO Smith Vertex, 96% efficient)
will last for 15 if not 20 years, but it will need replacement sooner
than nearly every other major component in the building. The system is
also designed for adaptation.

Thanks for listening - Dan Whitmore, Black Bird Builders

[Hayden Robinson]

Regarding the use of heat pumps in attached, unconditioned spaces: Is it
counterproductive to be creating a thermal buffer (the attached garage) and
then locating an air conditioner in it (the heat pump), thereby increasing
the delta T between the house and garage? Or am I over thinking this?

Hayden Robinson Principal
HAYDEN ROBINSON ARCHITECT
206.691.3445
www.haydenrobinson.com

[Eric Storm]

Thanks everyone for the continued thinking on all this.

 

Based on what I found in a few different projects, I think George's 3rd point below (surface to volume ratio) is probably the largest culprit.  I realize you have to work with what you are given.  I had a client whose design was never (!) going to reach PH standards because the house shape wasn't compact enough.  I tried all kinds of things, but the shape remained the single largest influence in that design.  All I could say to the client was, do the best you can but it won't reach PH.

 

So while there are many things to try, at some point a single design decision, or more often a combination of them, will become the limiting factor.  It may or may not be a critical one that prevents reaching the PH standard.  If it is, you just have to decide how firm that design decision is and how important PH is for the project.

 

My two cents.

 

Eric Storm

 

 

George wrote on Tuesday, December 21, 2010 1:45 PM:

6.     ...     This house is struggling for four

[Eric Storm]

I suppose I should have added why I didn't think the other reasons were as likely to be the main issue.

1) Larger houses TEND to pass PHPP more easily (all other things being equal).

2) Crawl spaces are often insulted to higher levels than slabs, and so should not be the problem.

4) All-electric is not itself likely the issue but rather how the electricity is used.  Resistance heating does use a lot.  More and less efficient appliances and lighting can also add up.

 

I am not making any definitive claims here, just personal observations.  I'd love to hear what others have found in their modeling of different projects.

 

Eric Storm

 

 

From: George

Sent: Tuesday, December 21, 2010 1:45 PM

6.  .....  This house is struggling for four

[graham]

We should do what we can to address climate change, but we cannot
afford to do everything - we need to do what is most cost effective.
You are right to be concerned about the cost effectiveness of a solar
thermal system (or any efficiency measure) as every measure has
diminishing returns. Rather than look at PHPP as being "biased"
against PV, perhaps look at what the software is saying as a reality
check. Essentially what it is telling us is that "if you wish to
design a building with very low source energy consumption (Passive
House) and you wish to use an dirtier energy source to heat it (grid
supplied electricity) you need to use less of it on site." That's an
objective reality. I think that under these circumstances, you may
well find that additional insulation to lower the heating demand is
cheaper than either a larger solar thermal system or a PV system -
shredded newspaper is pretty cheap, relatively speaking.

In terms of how PH treats renewable energy, I do not see an
inconsistency. If you install a solar water system, you offset the
site energy demand for heating or hot water with it, and assign the
pump electricity consumption to the "auxiliary electric" sheet. If you
install a PV system, you offset site electricity usage by assigning a
PE value of 0.7 to whatever consumption the PV system covers. The
excess is recognized as a carbon offset, which is exactly what it is.

As for PV net metering, I do not have an issue with the carbon offset
aspect of it, but with the fact that it is quite misleading to people.
Trying to supply our society with renewable energy is a VERY, VERY
difficult challenge, and "net-zero energy" via grid-tied PV is not a
solution, it is a obfuscation. There are only two problems - night and
winter!!! In terms of a societal strategy for carbon reduction,
rooftop PV is not even close to the most cost effective solution in
most locations.

Take a look at this map (http://www.solar-catalog.com/info/
insolation_solar_namer.html) and tell me why we as a society should
subsidize PV installations in Seattle (or for that matter, most of the
US.) Inyokern, CA is where it's at! The same PV panels in Inyokern
will generate 7.66/3.57 = 2.15 times as much energy than in Seattle on
a yearly basis. As a society, we should make rational decisions about
the most cost effective path to sustainability. In most situations we
are not at a high enough level of building performance to make the
switch to PV from efficiency cost effective. Again, this is not the
case for consumers on a project by project basis, but that is because
the market is distorted away from the fundamental fact that the most
immediate and effective source of renewable energy is efficiency.
Check this out: http://public.shns.com/node/43594 To meet current US
energy needs with solar, we need to cover 1.7% of the country. Not
much? That's about the same area as all the paving in the US!!!
(61,000/3,790,000 = 1.6%) Source: http://answers.yahoo.com/question/index?qid=20070719230638AAVVZR0

To paraphrase my "favorite curmudgeon" Nobel-prize-winning physicist
Ernest Rutherford, "We don't have much money, we're going to have to
think!!!"

PV and solar hot water ARE fundamentally different. Heat is relatively
easier to produce, easier to store, but harder to transport.
Electricity is harder to generate and store but easier to transport.

Back to work,
Graham

[tombalderston]

what a great discussion -

In terms of the carbon emissions and all electric - basically
electric demand is still exploding in most of the country and the grid
is more or less all one - or at least I think about three around the
US.

my two cents is if you are going to use electricity thermally use a
heat pump, though I don't think it really matters in PH's you should
see the bills on some of the existing homes I audit - 35,000 KWH/
year! Even after talking with Jeremy and seeing his Fracking slides
I think Nat gas has a place.

In terms of priority though, what we may need the most is to have the
house charge the car. Alaska is running out, and we in the NW are
on track to become some of the prime consumers of Tar sands Gasoline
from Alberta, where every gallon is made with 3 times the CO2
Emissions.

I like "winning the oil endgame" by Mr Lovins... Nat Gas is a
valuable transition fuel but most of it should move to co generation
and fueling vehicles. Perhaps we could convert our beloved belching
ferries to it. I don't really like any fossil fuels but I am still
reccomending swithching electric water tanks to thankless gas wherever
possible. The NW grid power is essentially 30% coal and another big
chunk Nat Gas to electric delivered at very low efficiency.

Set me straight George!