Outdoor, Gardens, and Rooftop At a net-zero home in San Francisco, the house's green roof is more of a brown roof: a desert-like array of native and non-native succulents that require minimal irrigation. The soil area is maintained with motorcycle tires (including one from a Harley hog), which control erosion. Composting takes place here as well.  Photo 7 of 8 in This Net-Zero Residence Might Be the Greenest Home in San Francisco by Tiffany Jow

This Net-Zero Residence Might Be the Greenest Home in San Francisco

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At a net-zero home in San Francisco, the house's green roof is more of a brown roof: a desert-like array of native and non-native succulents that require minimal irrigation. The soil area is maintained with motorcycle tires (including one from a Harley hog), which control erosion. Composting takes place here as well.