The Mill Valley Guesthouse is a stunning example of the art of design and the possibilities of sustainable construction. Built by Turnbull Griffin Haesloop of Berkeley, CA in 2015, this 640-square-foot guesthouse is situated in an existing small-level clearing at the top of a steeply sloping Mill Valley lot surrounded by mature cedar and redwood trees.

The guesthouse is designed to serve multiple generations and functions. It is a guest room for visiting parents and friends, a media room, and a hangout space for teenage children. The porch and media room are situated on the more open side of the site, while the guest room is tucked into the trees. The result is a beautiful and functional structure that blends seamlessly into its surroundings.

One of the most striking features of the guesthouse is the flat roof punctuated by round skylights. This design choice extends the dappled light of the surrounding tree canopies over the expansive porch and indoor spaces. The wood siding allows the walls to blend in with the trees, while the porch ceiling and skylight pattern become a playful façade as seen from the house and backyard below.

The Mill Valley Guesthouse is also a prime example of sustainable construction. The porch, cool roof, closed cell insulation, LED lighting, and high-efficiency boiler keep the energy loads minimal, exceeding Title 24 by 33%. This means that the guesthouse is not only beautiful and functional, but it is also environmentally conscious.

Overall, the Mill Valley Guesthouse is a triumph of design and sustainability. It is a beautiful structure that seamlessly blends into its surroundings while providing a functional space for multiple generations and functions. Its sustainable construction and energy-efficient features make it a model for eco-conscious design, proving that it is possible to build beautiful structures while still being mindful of the environment.