Abstract: A building envelope system includes several elements that aid in reducing heat transfer. Panels combining insulation and radiant barrier materials, a weather-resistant textile (e.g., canvas) cover, tube insulation, a vestibule and strip curtains can all contribute to reducing heat transfer and, correspondingly, reducing energy requirements for heating and/or cooling. The panel can include a tongue and groove or similar (e.g., dovetail) coupling allowing two panels to mate. The panel can include a top insulation layer, top air gap layer(s), radiant barrier layer(s), bottom air gap layer(s), phase change insulation layer(s) and a bottom insulation layer. By including an air gap on both sides of the radiant barrier, the radiant barrier is effective at reducing heat transfer in and out of the shelter.