I am in the process of replacing an Oil Furnace (died) and straight 5 ton a/c, Trane outdoor unit, (14 years old). All 3 contractors are pushing Lennox systems. Biggest concern is IAQ, then cost. House is a block, ranch, 1966 vintage, 2600 sq. ft., new windows and wall insulation added. Located in Central FL. We are taking out the old sheet metal duct work, branches and returns. Have had a serious mold problem with significant health issues for myself and daughter. Dr. and remediation specialist recommend replacing everything. Mold was in the walls from very negligent window install. Have plaster walls and never saw any signs until too late... The HVAC estimates are for the XP19 4 ton HP (heat load calc done), variable or non-variable fan at 4, 5 and 5.5 ton, 7000 t-stat, new return plenums and Lennox PureAir. MYQUESTION: (1) Do we need the XP19 or would the XP14 save enough $$ to step down? (2) VS fan seems to be a no brainer, but what size and model? The indoor unit is in the garage, no a/c. (3) Is the PureAir worth the initial cost and annual maintenance? --VOC's are a concern as new material going into the house after remediation and 2 of us have asthma. Do we need an additional UV above the coil? (4) 2 companies want to do all FLEX Duct, 1 co. wants to do rigid Fiberglass ductboard with flex branches. What type of duct work is best? It is in the attic. (5) Should the return plenums be a certain material and what about filters here? (6) Fresh air ventilation/dehumidifier? Can not open windows year 'round due to severe indoor and outdoor allergies. (7) Cost is definitely a concern.
ANY HELP is greatly appreciated!