Energy Efficient Fenestration Assembly

A building energy system comprising:

• a building enclosure having an interior and exterior, the building enclosure comprising at least one wall separating the interior and exterior and comprising an opening;
• and
• a fenestration assembly enclosing the opening in the wall, the fenestration assembly comprising:
• a frame having at least four edges surrounding first and second sides to be partially covered by building material, the frame defining:
• an opening from the first side to the second side;
• and
• a first pocket section next to the opening and sized at least equally to the opening,
• the frame comprising:
• an insulating mullion pocket between the opening and the first pocket section;
• and
• three insulating edge pockets within edges of the frame surrounding the opening;
• an insulating section between the first pocket section and one of the first or second sides of the frame;
• and
• a first sliding glass assembly supported on a bottom edge by roller carts moveable within a raceway of the frame, the first sliding glass assembly capable of sealing the opening and moveable between:
• a fully-closed position in which the first sliding glass assembly is located substantially within the opening and seals the opening;
• and
• a fully-open position in which the first sliding glass assembly is located substantially within the first pocket section of the frame,
• wherein the first sliding glass assembly comprises two or more glass sheets that are spaced apart and sealed at perimeter edges of the two glass sheets and features one or more low emissivity coatings facing at least one glazing cavity between the glass sheets and where the center-of-glass provides more thermal resistance than the perimeter edges, and
• wherein in the fully-closed position, the perimeter edges of the first sliding glass assembly are buried within the three insulating edge pockets and the insulating mullion pocket of the frame.