Founded in 2005 by David Yama and Karen Mar, San Francisco-based Yamamar Design Studio is dedicated to the principles of green design. The firm works closely with contractors, specialty fabricators, and regional suppliers, sourcing local materials and building systems. For this Mill Valley house, the firm made use of sustainable materials like high-fly ash concrete, untreated western red cedar, reclaimed hardwood flooring, photovoltaic solar power, and locally sourced ceramic and glass tile. Sited in a grove of eucalyptus trees, the house maximizes the clean air of the Pacific and the southern light with natural ventilation and optimized daylight; a grownup version of every child's fantasy tree house. To see more of the firm's work, go to Yamamar Design Studio.

Above: Standing Seam Roof with Kynar paint finish.

Above: Sited in a grove of eucalyptus trees, the Mill Valley house takes full advantage of the southern light. The exterior wood siding is FSC-certified STK (Select Tight Knot) Western red cedar.

Above: The light washes over the deck and into the house through Composite Bi-Folding Doors, which feature wood on the interior and hard-wearing aluminum on the exterior, reducing condensation and heat loss and saving on energy costs.

Above: Optimized daylight floods the interiors; even the bathroom is light filled thanks to a row of clerestory windows.

Above: The flooring material is Reclaimed Hickory Wood. Mill Valley house photographed by Bruce Damonte; contractor, Brad Chalstrom.

For a local school auction, David Yama collaborated with like-minded local dads Eitan Spanier (a fabricator) and Konrad App (a solar expert) on this Treehaus. The trio spent several weekends building the structure, using a combination of salvaged and donated materials. Presto: a micro-Yamamar collaborative, homegrown project for some very lucky children.

Above: Cheerful residents enjoying their treehaus. Photos by David Yama.