Compact but generous volumes interconnected by an expansive, sweeping ceiling over the entire main floor create the “Right-Sized house” free of unused/wasted space.Two counter posted butterfly roofs supported by a series of ’stretcher’ beams on round steel columns create the house’s dynamic composition. Integration between form and function, building and landscape connects the use of the workshop with the architecture of the space through spanning butterfly roofs, floated floors, fine detailing and natural wood materials. The Muskoka River House treads lightly on the landscape it embraces through the implementation of passive strategies and integrated design. Large roof overhangs - entirely constructed from R40 SIPS (Structural Insulated Panels) provide excellent Summertime shading to large expanses of thermal glazing - ideal for passive solar heating in the Winter. A low-albedo roof membrane reduces Summer heat-gain, and provides opportunity for the addition of a green roof later on. These overhangs also provide significant outdoor amenity areas during inclement weather, and protect outdoor furniture. The continuity of the ceiling plane and soffit helps extend the interiors with the exteriors - essential in establishing a connection to and appreciation of the site.While we considered a geothermal system based on the Muskoka River, the cost and efficiency were not well suited for this project. Space heating is delivered by a propane-fired, zoned, in-floor radiant system. A heat-recovery-ventilator (HRV) Natural daylighting washes the interior from high transom and clerestory windows. Marvin-Integrity fibreglass windows were used for excellent value and thermal performance (R3.5) Insulated concrete forms prevent wasted form lumber for the slab-on-grade foundations, and R40 Walls and Roof minimize heat-losses.