The Iowa Nest Residence was featured on the cover, and in a feature article, of the May/June 2020 issue of ICF Builder Magazine. The issue focuses on green building, energy efficiency, and Passive House projects.
The Nest Residence won the 2020 ICF Builder Award in the category of Small Residential. The annual project-of-the-year competition is widely regarded as the biggest event in the Insulated Concrete Forms (ICF) industry.
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.
The 13th edition of Mechanical and Electrical Equipment for Buildings (AKA “MEEB”) has just been published by Wiley. Chapter 1 on Design Process prominently features the Iowa Nest Residence as an exemplar of high-performance design — incorporating much of the material that has been discussed in detail on this blog.
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.
Things have to come through the walls, roof, and floors — even in an airtight house. How do we detail these elements in a way that (1) keep bulk water out, (2) meets our ambitious (Passive House level) air-tightness goals, and (3) avoids risk of condensation? Here are my details.
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:
This past weekend was a big milestone: we passed our initial blower door test, exceeding our airtightness target of 530 CFM @50Pa (a target based on Passive House standards as well as early energy analysis). Here’s what we learned about our air barrier.
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.)