This all-redwood cabin on the banks of Corte Madera Creek in Portola Valley was originally constructed as a summer cottage during the early 20th Century. Bucking the trend of demolishing small, older homes in the area, the owners decided to keep the old-growth redwood interiors intact and utilize Passive House building techniques. These include a super-insulated and airtight exterior envelope, as well as a heat recovery ventilator system that will enable the house to use only modest amounts of generated heat to stay warm in winter. Super-insulated glazing, all-operable windows, and energy-efficient appliances will keep energy use at a bare minimum. A future phase to add a photovoltaic array will allow the home to produce enough on-site electricity to make it a net zero energy property.