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Like many cities in the U.S., Duluth, Minn., has been experiencing an inflationary and undersupplied housing market. There’s an extreme scarcity of homes suitable for the city’s very cold and changing climate. Drawing from decades of experience in the custom design market, we set out to help fill this gap by creating a series of stock house designs that are net-zero-energy ready and ready to build. Our approach is informed by three primary goals:
- To develop comfortable and appealing all-electric homes with exceptional indoor environmental quality, durability, and low energy requirements.
- To use cost-effective assemblies with readily available materials.
- To create construction documents that are thorough and easy to understand, even by builders unfamiliar with high-performance home building.
The Evergreen House is our one story, three-bedroom, two-bath prototype. At 1500 sq. ft., the Evergreen House is a good fit for, say, an older pair looking to age in place, or a family of five at the start of homeownership, or anything in between. The first Evergreen House was completed in the fall of 2023. Built by a local nonprofit housing developer, it was sold to an income-qualifying, sustainability-minded retired couple. In its first year, the Evergreen House completely offset its consumption with net-positive solar production. In 2024, it used a third of the energy compared to a code-built home in Duluth that was built and occupied at about the same time.
In a climate like Duluth’s (zone 7), an energy-efficient housing stock is deeply needed for the safety, comfort, health, and stability of our community members. For us, the Evergreen House demonstrated that net-zero-energy performance can be achieved with familiar details, assemblies, and building strategies—even with a builder who hasn’t built to this standard previously. In this article we’ll take a deep dive into the Evergreen’s design and construction and…
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6 Comments
In situations where it's uncertain whether or where supplemental electric resistance heat may be needed, I wonder whether removable plug-in wall mounted heaters might make sense? They could be stored elsewhere when not needed.
Something like these: https://www.eheat.com/envi-120v-plug-in-electric-panel-wall-heater-3rd-generation/
Thanks Malcolm. Nice idea. I'd still probably lean toward hard wired rather than plug in, at least in a few locations, in part because the "easiest and most memorable" place to store a few of these might be where they're needed. And with thoughtful placement, they wouldn't be in the way of furniture. I love the product you linked to, and it's made in the U.S.
Nice design, and great detailing and other information.
I do NOT recommend hanging ASHP outdoor units on framed walls, though--the vibrations travel a long way. I don't even like them hung on concrete walls.
Thanks for the feedback Michael. With the amount of snow we get in our climate, I struggle to come up with good locations for those ASHP outdoor units. We've done a wall-hung mount on a mechanical room wall several times with good results - meaning the occupants said there was no discernible noise or vibrations. I wonder if the thick continuous insulation layer helps mitigate that problem, but maybe we just got lucky. I like to have a little roof over them, and if they go on a slab, it's like we're building a special "porch" just for a piece of equipment.
I'm sure every project is different. I learned about the issue on a house with 12" double-stud walls with cellulose, including the attached garage, and the outdoor units were on the garage walls, not the house walls. On other projects I have had contractors locate them on walls against my recommendation with apparently no problems. A client for a new home last year has excessive vibration with a ground-mounted unit, apparently because the lineset goes straight from the outdoor units through the wall, so the vibrations carry through the copper. Now I know that providing a Z-bend in the lineset reduces that issue. Here in Maine, on the coastal side of the state, we rarely get more than a foot of snow at a time so elevating the outdoor units is usually enough to keep it out of the snow. "Porch roofs" area good idea!
Congratulations Rachel and Leah on your first prototype. I hope to see in person and learn more about your upcoming projects. Your final blower door number of 0.41 ACH50 is salutary!
I'm all in on the simple form and off-the-shelf materials. I especially like your use of metal panel siding over a mechanically-fastened WRB---it's both cost effective and eliminates the need for a rain screen. I suspect there will be more wide spread adoption of this siding type in the future, as homeowners embrace a more modern, functional aesthetic instead of trying for a "historic" style.
What is your opinion of Zip-R sheathing in place of the nailbase you typically use?
I'd also like to know why you decided on 2 bathrooms off the hallway instead of the more typical arrangement of a private "master" bathroom connected to a "master" bedroom (AKA "primary suite" or "owners suite").
I just completed my second net-zero home which gave me a chance to correct several errors made on the first one, including mounting the Air Source Heat Pump compressor on brackets that attach to the exterior studs of a double stud wall. Occasionally--not always--vibration and noise transmits through to the interior.
For this most recent project, the ASHP is mounted on a riser that is then mounted on brackets but this time, the brackets a lagged into the foundation wall. So far, we haven't experienced any vibrations through the structure and we're clearing the snow. Note: I had my contractor come back and attach lateral bracing to the brackets to prevent movement. Finish grade is the gravel, about 8" below the siding.
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