We just added a glassed in Cat 5 room to our west-facing lanai - about 220 square feet. Our situation is different though as it's insulated, low E, Argon glass. We raised the floor, removed the existing sliders and insulated the attic. We thought we'd need a mini split (around $6,500) but were able to get by with adding duct work to our existing 2.5 ton AC unit (around $1,800). Our room was finished a couple of days before we left for the summer but we monitor it (and other rooms) with ecobee Smart Sensors - the lanai's temp is the same as the rest of the house.
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Wisconsin, Indiana, California, Tennessee, Arizona, South Carolina, Florida
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