The Passiv Report

Passivhaus first, then LEED

LEED can be a great addition to commercial construction projects, but if you don’t address energy performance, you can’t call your building “green”.  

We founded Passiv Science to help teams across North America repeat the success we’ve had at Structures Design/Build in delivering market rate high performance Passivhaus (aka ‘Passive House’) buildings.

But why the focus on Passivhaus? Why not LEED?

It’s not an either/or question (see “Passivhaus vs. LEED – A False Dichotomy.”) Our Passivhaus projects nearly always qualify for LEED certification and as green building professionals we’re trained in both certifications. Each of our Certified Passive House Consultants (CPHCs) is also a LEED Accredited Professional.

Passivhaus and LEED are complementary. Passivhaus brings a laser-like focus on building performance that guarantees both transformational energy efficiency and building durability. But by design, Passivhaus doesn’t address broader sustainability concerns like stormwater management, urban design, bike racks and the like. LEED, on the other hand, does address those broader concerns, but it can be inexact, even weak with energy performance. LEED certified buildings can actually perform below energy code, something unheard of in Passivhaus construction.

Because it casts a wide sustainability net, LEED can be a great option to consider. But our feeling is that if you don’t address building energy performance first, you can’t call a building “green” or guarantee its durability. So we say, “Passivhaus first, then LEED.”

A key distinction of Passivhaus is that it’s a physics-based, holistic building analysis method.  While both Passivhaus and LEED employ energy modeling to predict the energy performance of buildings, any energy performance prediction method is subject to the old adage: “garbage in, garbage out.”  Very few buildings that use LEED energy modeling find that actual performance falls on the predicted line. Passivhaus, on the other hand, hits the prediction time and time again.

An energy model is made up of one part knowledge, one part experience, one part art and one part voodoo. The issues with the accuracy of all energy modeling software is the combination of:

  1. Knowledge and experience of the modeler of both the program algorithmic assumptions and energy modeling in general.
  2. Translation of the model into the design drawings.
  3. Field implementation of those designs.
  4. Commissioning and testing of the systems (including the envelope).
  5. Education of the users as to the behavioral assumptions made in the model.
  6. Ongoing performance monitoring to keep both the users aware of their behavioral effect on the energy consumption the building and the building manager abreast of the system performance to ensure systems are working as designed.

This is where Passivhaus’ laser-like focus comes in handy. Passivhaus’ raison d’etre is energy performance. The Passive House Planning Package is unrivaled in its ability to predict the energy use of high performance building designs. Certified Passive House Consultants are trained to go deep with their energy modeling and the implementation of their high performance construction detailing in the field. And the Passivhaus community routinely implements verification and monitoring of completed projects to ensure actual performance meets expectations.

So the “math” is simple: superior energy model + tenacious modelers + focused field implementation + verification and monitoring = predictable performance.

LEED can be a great addition to green building projects. But if you want a building that performs well, performs as predicated, and will last a very, very long time, then “Passivhaus first.”

– Adam

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