4.15.2012
How Passive House Makes Net Zero Energy Homes A Reality
Posted by http://baosol.blogspot.com/
Learn more about Passive House on RM-PH.com
If you have lived off-the-grid for awhile like I have, you
may also find the newly found interest in net zero building a bit amusing. Most
of those who tout NZE do so from the luxury of a grid safety net, and those who
want to go "off-grid" are typically more motivated, I think, for a
spiritual or political purpose than the technical or environmental challenge.
They never actually move to the cabin in the mountains or the yurt in the
plains, or take the experience to fullest and design a stand alone system. But
now the next thing is being served up in the form of Net Zero Energy living, a
rather Zen-like approach to a built environment where one takes nothing out and
ask for nothing in return.
The exciting thing is that technically speaking NZE is
actually not too hard. What you need is a really, really big roof. The average
home consumes just shy of 40 kWhs of electricity a day which very roughly
equates to a 10kW solar system. At 10 watts a square foot you have a 1000
square feet of glass and silicon on the roof should be enough for an average
house. Yikes(!) basically a very big shed roof covered in $50,000 or so dollars
to make NZE a reality. I think I am probably low balling these numbers but they
give the picture. Builders got smart and started lowering their home energy use
as well to make NZE a reality, but let's face it, a really good home now is
considered 30% better than code, and we really haven't talked about all the
crap plugged in. So now the trend of NZE homes is looking at a upgraded house
shell still with a big ol' honken solar array. The market message is if you
want NZE it's going to cost you. Most folks are like me who could not afford
anything near that, so I put up a tiny array and worked really hard at making
sure I did not need the energy in the first place. Actually it wasn't hard to use
1/10th the average energy.
In the past year I have been working with group developing
Rocky Mountain Passive House and while it took me a while to get to Passive
House here I wanted to make the point that it's not about making energy that
really counts for net zero energy consumption, it's about not needing it in the
first place. That is what passive is all about. We cut 90% of all energy out of
the equation which means that the building needs a much, much (much) smaller PV
array. The size depends on how much energy the occupant uses to be fair, but we
aim to give the project a real head start to NZE.
The dollar equation is even better. While a Passive House
costs more than an average house to build for now, a NZE Passive House cost
less than a comparable NZE project, and you get your upgrades for free (like
some cheesy sales pitch). Think of it as opportunity savings: getting
incredible windows and doors and a state-of-the-art envelope which equals
comfort and craftsmanship for less money than plucking it down for a stack of
PV on a roof, which frankly is not really a lifestyle enhancement. Get rid of
the HVAC equipment costs and up-keep and the savings are durable and long term.
While your spiritual or philosophical needs for low impact housing is met -
http://rm-ph.com/about-the-passive-house-standard/comfort/ your actual
comfortand budget is taken care as well. With Passive House your roof's solar
collection potential is now available to feed things like an electric car you
buy in a couple years, which makes your overall energy and environmental impact
dramatically improved as well as future proofing your energy needs. Passive
House makes the potential of a good energy citizen a reality, reducing the
demand to a trickle and providing a genuine potential for eliminating dirty
energy from your life both technically feasible and long term affordable.
Net Zero Energy (or if you prefer Zero Energy Building) can
be measured in a handful of ways depending on what you include: embodied
energy, equipment life span, line loss from energy supply, simple net-meter
measuring. For instance if your meter says '0′ net energy consumption for the
year this will not account for line loss or inefficiencies at the energy source
like the coal plant, so the devil of what is reality is in the details.
Producing energy onsite is not a panacea either; it typically is overused when
system thinking is not applied and a market driven by products takes over.
Don't get me wrong, I love photo-voltaic technology because it is solid state,
will last longer than your roof and is utterly dependable. I have been off-grid
for 16 years and no, it is not NZE as I use wood for heat and propane for hot
water and cooking. For that you really need to be a good citizen and feed the
grid (just without the extra mortgage).
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