AIA ZNE Primer cover image

The American Institute of Architects California Council recently published the Zero Net Energy Primer. I had the privilege of developing the Primer for them under a contract with PG&E. The Primer (if I do say so myself) is a handsome, concise, and accessible guide — a mere 24 pages, including lots of pictures of ZNE homes of all flavors (small, large, single- and multifamily, luxury and affordable). The AIACC’s goal in publishing the document is to ease the task facing California architects with the roll-out of the State’s 2019 energy code (“Title 24”). The new code will go into effect January 1, 2020 and — while it doesn’t quite get us to ZNE — represents a significant advance in residential energy performance, and the first time that homes will be required to install renewable energy systems. (Of course, there will be byes for projects where it’s simply not feasible to install them.) The Primer will, I hope, help architects get a handle on the ZNE requirements ahead of the looming 2020 deadline.

Kudos and many thanks to designer Debra Turner for the engaging design, and to architect Steven Lee for his terrific illustrations.

From Predictability of Energy Use in Homes, Lachut, D., et al. (http://www.cs.usfca.edu/~srollins/pubs/igcc14.pdf)

Lots of people complain about energy models — specifically, how they don’t accurately predict how much energy the occupants of a home (or building) will actually use. This complaint misses the point.

The REAL problem with energy models is that there is widespread confusion about what they can/should be expected to do. Predicting actual energy use for one specific household is not on the list of realistic expectations. Approximating the amount of energy a reasonably large aggregation of households might use? Yes, perhaps, in skillful hands.

The main thing that energy models can and should be used for is to compare the relative effects of different variables on a building’s energy performance, holding constant certain assumptions about the occupants’ usage patterns — which, even in the best circumstances, are fundamentally unknown and must be generalized.

It’s important to remember that a home (except in extraordinarily rare instances) outlives any particular set of occupants and behaviors many times over; those are subject to frequent change. Even one set of occupants will change energy-using behaviors after a time — for example, as toddlers outgrow bathtubs and graduate to shower usage … and then avoid bathing at all … and then evolve to multiple changes of clothing and multiple showers a day (think: soccer and muddy shorts and shoes).

Thus it’s a pointless exercise to attempt a precise fit of behavioral assumptions to a specific set of occupants, or think that we can predict their energy use for any but the most fleeting time period. What we should be doing is designing homes to efficiently serve any household that might reasonably be expected to live there over the life span of those homes.

\With that understanding, and the use of standard occupancy assumptions*, we can certainly use models effectively to compare the relative effects of different features on energy use.

AIBD California Society 2014 Annual Conference, April 2nd – 4th

Enough for today about past events — this one is still on the horizon. Next week, in fact!

In San Bruno, about 2 miles from where I sit as the crow flies, Skyline College’s Solar and Building Science department will be hosting the California Society of the American Institute of Building Designers‘ annual conference, April 2-4. This year’s theme is “Building Design + Building Science.” Joining keynoters Rick Chitwood, Gavin Healy, and Dan Perunko, I am honored to be playing a major role in this gathering of designers and builders from throughout the state. I’ll be teaching all day Thursday, April 3, concluding with a keynote address entitled, “The Persistent Pursuit of Practical Passion.” (I confess, I have a silly streak a mile wide … though I promise the content will be completely serious.)

All are welcome, not just AIBD members — come one, come all architects, general contractors, subcontractors, engineeers, HERS raters, BPI analysts, interior designers — this is for you if you’re noticing that the topic of building science seems to be gaining in importance along with energy performance!

California state agencies are mobilizing to get all of the State’s new homes to be zero net energy (ZNE) by the year 2020, and all new non-residential buildings to be ZNE by 2030. In order to accomplish this ambitious goal, all of us in the building industry are going to have to become much more savvy about building science. This event will be a great opportunity to get a jump on your competition — or hear the latest developments, if you’re already working at the intersection of good building design and superior building performance.

View the full conference schedule here. Register here.

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