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.
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.)
Once we evaluated which passive design strategies were most important when it came to energy use and thermal comfort, we asked the question: which will give us the most bang for our buck? Rather than engage in a detailed (time-consuming) cost analysis at this early stage, we did a simple overlay on our existing sensitivity analysis — which provided some key insight for remarkably little effort.
The Iowa Nest is a Net Zero Energy-targeted residence in rural Iowa. It is designed to supply 100% of its energy needs; to be comfortable without conventional air conditioning; to fit into the landscape; to last for hundreds of years; and to do all of this on a conventional construction budget.
My first visit to the site: a cold, cloudy January day, the landscape rendered in shades of gray-blue and brown. The owners and I trekked across the expansive property — the “finger fields” to the north, the ridge of the former railway, the plateaus and wooded hillsides — searching for the right location for the house.
In the end we all agreed on a south-facing hillside with expansive views of a meadow and a pond, a large stand of trees to the west, and a winding approach through a small field and a wood. It was practical — close enough to the road for access and utilities — poetic — with nestled into the earth, with just enough elevation to lend a sense of expansiveness to the views —and, importantly, ideal for passive design: the hill lends itself to earth berming; southern exposure allows good solar access; and the western trees provide shading from harsh late-afternoon sun.
As simple as these features seem, they are critical for achieving high performance at reasonable cost. Continue reading “First Site Visit: Siting the House for Poetry and Passive Design”