Seattle ranks among the top 10 most expensive—and desirable—places to live in the United States, so it’s no wonder the city needs to expand and diversify its housing options. One of many solutions to the housing shortage is the accessory dwelling unit, or ADU. ADUs can be either attached to an existing home (AADU) or detached and located on the same property (DADU). Most of the residential space in Seattle is zoned for single-family homes (now called “neighborhood residential zones” to be more inclusive and accurate), so finding ways to increase density in these areas is imperative to creating more housing.
ADUs also provide a flexible housing option. They are typically compact, under 2000 sq. ft., and thoughtfully designed to optimize space and accommodate small-home living. They can be used as rental units, guest houses, multigenerational family accommodations, or even as for-sale homes, which are allowed in Seattle if the homeowner creates a condo association between the main house and the ADU. There are other aspects of ADUs to like also. They usually fit well into the “fabric” of the city stylistically; often they are designed to match or at least complement the main house, and they generally can’t be higher than two stories tall. Plus, for a first-time home buyer, they are more affordable than many homes on the single-family market. That is certainly true for new construction.
My company, Targa Homes, has focused on building high-performance homes for the past five years. For this reason, in 2022, a homeowner approached us to build a DADU for her daughter, who would soon be relocating to Seattle. My employee Matt Kull and I have a strong background and understanding of building science and sustainability. In my case, that knowledge was gained as a Passive House rater and Built…
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8 Comments
Very cool build, Sean. As a fellow Seattle-area resident, thanks for doing what you can to keep Seattle green!
Thanks! Appreciate it
Sean,
This is a really nice project on a number of levels. It looks like a building that adds to the neighbourhood in every way. Good work!
Really appreciate it, thanks Malcolm!
Really like the wood plank floors. How wide are those?
It's an engineered product by Valinge. These are 8-1/4" but they also come in 10-3/4"!
https://www.ghsproducts.com/valinge-brushed-hardened-wood-flooring-misty-white-oak-select/
Thank you for sharing your work to create attractive and high-performance ADUs!
Thinking about scalability, I would be interested in understanding the:
- Site energy consumption target (before PV)
- Design space heating load
- Approximate total project cost
Hi-
- Our rater did a REM/Rate model, which showed expected annual consumption of 5964 kWh without PV. Of course all models are wrong for what it's worth :)
- I did a load calc using https://hvac.betterbuiltnw.com/ which showed 10,300 BTU/h heating, 17,700 BTU/h cooling
- Cost approx $540K
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