A ‘fabric-first’ approach refers to a design focus on high-performing building enclosures, whether new construction or retrofit. Generally, this means super-insulated, air tight, high-performance doors and windows, and eliminating thermal bridging. The building can then be conditioned using much smaller, ultra high-efficient HVAC (heating, ventilation and air conditioning) systems resulting in greater indoor air quality (IAQ) and comfort. Envelope upgrades for deep energy retrofit are typically from the outside and referred to as ‘over-cladding.’ Fabric first approaches allow for significant energy demand reductions and greater resilience during power outages.