NET ZERO ENERGY, REALLY???

May 29, 2014

I suppose a blog is as good a place as any to get out your pet peeves.  One of mine is the “Net-Zero Energy” label on buildings that are still in design.  As I write that, I am thinking “Oh crickey, I bet I am guilty of that.”  Yes, I may have gotten sloppy myself writing project descriptions and didn’t properly qualify what Net-Zero energy means.  If you ever catch me doing it, tell me!

Here’s why it matters…a building cannot BE net-zero energy until after it is fully operational for four seasons.  During design, a building can be “modeled to be Net-Zero Energy” or  “Net-Zero Energy Capable” or “Net-Zero on a Wing and a Prayer” BUT it is not ACTUALLY net-zero until you have a year of data to back it up.  Our first net-zero energy project was the development of two residences (for twins no less) in 2006…these were actually, um, negative-energy (?) projects because the sisters received checks back from the utility.  We then had a Quaker meeting house verified as Net-Zero Energy.  We recommend Net Zero Verification through International Living Future Institute.

Architects don’t like to say it and clients sure don’t like to hear it but design is based on A LOT of assumptions.  How many iPhones will you be plugging in?  How cloudy will it be in January?  How will those new German windows really perform?  How disciplined are you going to be about night flushing in the swing seasons?  For this reason, if you want a net-zero guarantee, you have to overdesign.  If you want a ‘shoot for’ net-zero, you can cut the design closer to the bone.  In all cases, owners have to get on board with the net-zero program which means paying serious attention to operations.  In a net-zero building, you don’t just live in it—you sail it.

Wait, wait, what about modeling??  Doesn’t that predict what is net-zero?  Modeling is an excellent tool for making decisions based on relative information (this orientation is about 10% better than that one) rather than absolute information (this orientation will save you exactly 1000kW per year).  Through modeling, you can show how a building is net-zero energy capable based on a series of assumptions.  If any of those assumptions is incorrect or changes, then the facility is no longer net-zero.

This is a meaty topic so let me summarize in bite-sizes:

  1. No building is net-zero until verified.  Check out this resource.
  2. Modeling is a useful design tool and supports informed decision-making.  However, it does not provide absolute data and cannot realistically guarantee specific utility usage.
  3. Buildings don’t use energy, people do.  So, operations are a key part of the equation!

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