The house uses only three interlocking materials: a self-heated concrete floor that eliminates the need for space-consuming radiators; double-glazed windows that let the outdoors in while keeping out the cold; and eight wooden panels manufactured in a Denmark factory during the winter months. “The interior walls are birch plywood to add warmth and texture to the rooms,” Larsen says.  Danish Prefab Feels Much Larger Than Its 861 Square Feet by Laura C. Mallonee