Gravity-fed rainwater is collected from the rooftop. During rain the first 5 gallons of runoff flushes the gutters clean and is diverted to the garden. The rest is pre-filtered and stored in a cold water holding tank on the top floor. Excess water is sent to a cistern below the house which can store 2400 gallons for use in dry weather.
Water is filtered in stages according to its uses. Flushwater goes directly to its use without further filtering. Washwater goes through an ultraviolet sterilizer. Potable water passes through another filtration membrane before being circulated to the reverse-osmosis filter in the bottom floor to take out any chemicals, particulates or trace metals. When it comes out it's more pure than bottled .
Automatic shut-off faucets on the sinks and shower remind you of how much water you are using. Grey water from washing dishes and clothes is captured for washing cars, watering plants, and can flow to an ornamental garden. Composting toilets use only 8 ounces of water per flush.
The roof acts as a solar heat source for the water. Under a metal roof water tubes lie on top of a black absorbent material to capture the maximum amount of solar energy. Reflective insulation below this keeps heat from conducting to the living space. Hot water also provides radiant heat through tubes in each floor of the house. A wood-fired boiler provides backup during extended cloudy periods. A small electric water heater provides very hot water when needed.