Existing covered porch enclosure, 2 levels

Desire to enclose both spaces, upper and lower. Lower would need provisions for floor joists or possibly slab. Engineered plans for owner/builder to comply with local (89815) building codes. Also design replacement access from upper deck to lower level (stairs suffered from weather and poor care from previous owners). Longest side faces compass 240 degrees and want to add for solar gains via evacuated tube array to add heat to existing daylight basement and dwelling. Desire for 6 inch walls and improved windows, finish flooring, so adequate support needed without compromise to existing roof supports. Ability to work with lumber, residential steel framing, or structural steel. Desire most cost effective option.