It may be simpler to build a zero-energy home from scratch than to retrofit an existing structure, but buildings constructed in the 20th century are generally the most in need of upgrades for energy efficiency.
There are some simple modifications that can be made on existing homes to dramatically reduce waste, emissions, resource exploitation, and energy bills. The Canada-based Now House project has developed a replicable model for retrofitting World War II homes to near-zero net energy. Deterioration that comes with old age and the inferior quality of mid-century materials is the largest issue these homes face. As a rebuttal, the Now House focuses primarily on sealing the building envelope, replacing worn insulation, and installing solar panels. It’s a homeowner-friendly strategy that keeps costs and disruption down.