Thermal break for a fenestration unit

A fenestration unit comprising:

• a frame including a plurality of frame members, wherein the plurality of frame members includes an upper rail member, a lower rail member, a first stile member, a second stile member, the lower rail member including a first metallic extrusion and a second metallic extrusion positioned opposite the first metallic extrusion, the first and second metallic extrusions defining a space therebetween;
• and
• a thermal break coupled to the lower rail member, the thermal break located within the space, the thermal break including,
• a body of thermally insulating material defining a first side portion, a second side portion, and an intermediate portion between the first side portion and the second side portion,
• wherein the first side portion defines a first horizontal protrusion coupled to the first metallic extrusion and the second side portion defines a second horizontal protrusion coupled to the second metallic extrusion, and
• wherein the first side portion and the second side portion are asymmetrical about an X-Y plane.

A fenestration unit comprising:

• a frame including a plurality of frame members, wherein the plurality of frame members includes an upper rail member, a lower rail member, a first stile member, a second stile member, the lower rail member including two metallic extrusions on either side of the rail with a space defined therebetween;
• a panel coupled to the frame, the panel including an upper side defined along the upper rail member, a lower side defined along a lower rail member, a first side defined along the first stile member, and a second side defined along the second stile member, the panel including a set of rollers coupled along the lower side;
• an insulated glass unit supported within the panel;
• and
• a thermal break system defined along an isothermal plane of the fenestration unit, the thermal break system including,
• a first thermal break coupled lengthwise along the lower rail member of the frame, the first thermal break including a first body of thermally insulating material, the first body being asymmetrical about a longitudinal axis, and
• a second thermal break defined along a lower side of the panel proximate to the set of rollers, the second thermal break including a second body of thermally insulating material, wherein the first thermal break and the second thermal break are aligned along the isothermal plane.