Designing a Net Zero Home: A Map of the Design Process

The design of this home was, in part, a test of a design process—of a philosophy of design—known as performance-based design. The central idea is that performance analysis (energy, daylight, and thermal comfort analysis, among others) has a central role to play in informing design decisions at every step of the process.

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DAAPx Presentation: Summer House, Winter House

What does it mean to be “comfortable?” This presentation at the DAAPx Symposium on Experiential Design in September 2020 uses the Iowa Nest Residence to explore the idea of designing for “thermal delight” (a term coined by Lisa Heschong in her book of the same name). It discusses how comfort is far more than just air temperature, and how these additional physical sensations were used in the Nest Residence to maintain comfort largely through passive measures.

Seven Strategies for Net Zero Energy at Net Zero Cost

We set out to design a Net Zero Energy house at conventional per-square-foot costs. We got pretty darn close. Sans solar panels (which will be installed after two years of operation), the house came in at 8% less than a conventional new home. With solar panels, the house is still 2% less than conventional.

Here’s a full cost breakdown, and the seven strategies we used to get there.

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A Wood Stove in a Passive House

How should you design and detail a wood stove in an airtight Passive House? Here are some of the considerations, and the approach we used on this project.

First off: should you even have a wood stove in a Passive House? This is rightly a matter of some debate. It’s certainly not necessary, as our temperature data have shown: this particular house has proven it can stay habitable even through the coldest of cold snaps—maintaining ~55 degF even in -20 degF outdoor temperatures without mechanical heating.

And, a wood stove in a Passive House comes with downsides and risks:

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Slideshow: Achieving Net Zero Energy at Conventional Cost

Below is the slideshow I presented on April 20, 2017 to the Iowa Building Enclosure Council, and to a sustainable construction class from Hawkeye Community College.

The version below is slightly edited to make it easier to follow online. (I tend to avoid text in my presentations, which can make them difficult to follow without accompaniment.)

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Incorporating Analysis in Concept Design

I incorporated energy and daylight analysis as part of the conceptual design for the Iowa Nest Residence. This meant that early design discussions encompassed both traditional topics like floor plan layout, siting, and aesthetics, as well as performance criteria. The addition of analysis added a trivial amount of time, but proved incredibly valuable. Here’s how I did it — and what I will do differently next time.

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Can We Avoid Air Conditioning?

Iowa, like much of the American Midwest, has a treacherous combination of deep, cold winters and hot, humid summers. Could we overcome this with good passive design? Could shading, natural ventilation, earth berming, and the like obviate the need for air conditioning?

Here’s how I went about answering this question. This analysis was done in early design so that the answer could inform basic design moves.

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