On the roof. A copper roof can cost three times that of a shingled roof, but if maintained properly, it won't need to be replaced for a century or more (most roofs other than slate need to be replaced every 15-20 years). A reflective metal roof is more energy efficient than an asphalt roof and can save on the cost of air conditioning. There's also a huge aesthetic bonus: This roof will develop a beautiful patina that will continue to deepen over time.
Railings can also be made of found materials that were collected onsite. More Architect's Toolbox: Scale and ProportionMore:10 High Designs for the HandrailKeep Your Balance: Cool Railings