In 2005, actress Cate Blanchett and her husband, Andrew Upton, purchased the historic, 19th-century Bulwarra estate in Hunter’s Hill—a suburb of Sydney, Australia. A decade later, after adding a slew of eco-friendly amenities to the sandstone abode, the couple is listing the home for nearly $15 million. Featuring high-tech solar paneling to generate clean energy, hydronic underfloor heating, low-energy lighting, and a rainwater tank that recycles water for irrigation purposes, the house is an energy-efficient …