Once upon a time, all residential building was green. Nomadic Mongolians carted their felt-and-wooden yurts around on four-wheeled wagons. Celts kicked it in earthen ("cob") roundhouses made of wattle, mud and straw, while Spaniards and indigenous Americans perfected the art of the adobe dwelling.
Until the Industrial Revolution, residential building materials consisted of mud, straw, stone, timbers and other locally harvested ingredients. Sustainable by default, these homes met the needs of the present without compromising the needs of future generations. With the advent of railroads, however, it became easy for builders to acquire materials like steel from faraway places. Fast-forward more than a century and soon cheap, energy-inefficient McMansions ruled residential home markets.
Today, with global warming on the rise, more homebuyers are demanding green homes, and home builders are looking for cost-effective, sustainable ways to deliver them. Recent advances in green building technologies are bringing carbon-neutral and zero net-energy homes closer to reality. Before we get started detailing some of these advances, let's first look at green home building's golden ring: zero-carbon or zero net-energy homes.