Detached Accessory Dwelling Unit

Bellingham Gentle Density DADU (detached accessory dwelling unit)

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TC Legend Homes demolished an existing one-car garage and re-purposed the available space with a cozy, high-performance, 775 square foot, detached accessory dwelling unit (DADU) that includes an attached single-car garage. The RE Store handled the structure demolition to maximize recycling opportunities and minimize waste.

The DADU was designed from the ground up to be net-positive-energy, meaning it will produce more energy on an annual basis than it requires. TC Legend Homes applied the same approach and many of the same building techniques to this DADU as it does to any of its other homes.

Key Features:

  • A simple design to minimize exposed surface area

  • Orientation and window placement to optimize active and passive solar

  • Slab on grade with 4” under-slab insulation & Insulated concrete forms

  • Structural Insulated Panel construction (vice traditional framing) to reduce possibility of thermal bridging

  • Triple-pane windows

  • High-efficiency mini-split heat pump for heating & cooling and high-efficiency heat pump for water heating

  • HEPA High Efficiency Whole House Insulated Filtration System

  • 5.4kw photovoltaic solar system

  • Energy Star, EPA Indoor airPLUS, and 5-Star Built Green Certified

  • Home Energy Rating System (HERS) Index is negative 16!  (A typical new home has a rating of + 62).

Whatcom County DADU (detached accessory dwelling unit)

All photos courtesy of Jared VanderGriend

All photos courtesy of Jared VanderGriend

This family needed some room for the big kids to spread out. TC Legend Homes designed and built this accessory dwelling unit to meet their needs. The family gained a large garage, with 576 square feet of living space perched above, accessible to the main house via 2nd-story bridge.

Key Features:

  • A simple design to minimize exposed surface area

  • Orientation and window placement to optimize passive solar

  • Insulated concrete forms

  • 2nd floor Structural Insulated Panel construction (vice traditional framing) to reduce possibility of thermal bridging

  • Double-pane windows

  • High-efficiency mini-split heat pump for heating & cooling

  • Energy Star, EPA Indoor airPLUS, and 4-Star Built Green Certified

  • Home Energy Rating System (HERS) Index is 46.  (A typical new home has a rating of + 62).

Issaquah Rental Home

Rick had plenty of building experience, so when he decided to construct a detached accessory dwelling unit (DADU) on his large lot in Issaquah, he wanted it to be a hands-on project. TC Legend Homes built the highly insulated SIPs shell, and Rick took it from there. These photos show what an excellent job he did with the finish work. While the home does not have solar panels installed yet, it is oriented to make the future addition of PV simple.

We like this project because it shows how an owner who wants to get involved can save on construction costs and still end up with an air-tight, well-built structure that will last for generations. We also like how Rick made excellent use of his beautiful treed lot, adding another home near his main residence that will bring him rental income and add value to his property.