Divide 1600-CFM by an initial filter velocity of 300-fpm = 5.33-sq.ft. of free-open air area. Hart & Cooley A 25X20 only delivers 721-CFM; not HALF what is needed for 300-fpm velocity. . Therefore, 'two' 25X20's would only deliver 1442-CFM; you need to flow 1600-CFM at 300-fpm with a cheap 1" deep throw-away filter. You actually need a second 30X24 filter area 'to get above' what is needed for 300-fpm initial velocity. Best to use; but if can't...> Another 24X24 filter area; using both filters would then flow 1553 CFM at 300-fpm initial velocity through a new clean filter.; that is close. You could reduce the 4-Ton's CFM to 1550-CFM with no problem. Even 350-CFM per Ton might be a wise move; that is 1400-CFM. Unit is probably oversized & that CFM would provide better humidity control & improved COMFORT. This post was edited by udarrell on Thu, Jun 27, 13 at 15:57

Your max is the lowest bottom end potential cost. It will more likely be 30-80% more than that for something average in build quality. Depends on if you are in Kansas City, MO, or Alexandra, VA. That is if the foundation and garage framing can hold up a second floor, and the top plate heights at all line up with the home. And the home's main drain is on the same side of the house. Most likely one of those assumptions is not the case. You might have to tear down the garage and completely start over as a new build. And pay for a new sewer tap. If allowed. If the main drain is in the wrong spot, the project will never be feasible to do.

Hi, @Anglophilia Thanks for your reply. It's not about the money. We're a military family stationed in CO and are on a travel ban for at least the next four weeks. Before closing, we visited the house several times. It's such a long story...knowing we were moving to the Fort Hood area, we started searching online and found the home. Our daughter viewed it for us. We went to TX, did a home inspection, and were aware of all issues before purchasing. The previous owners allowed farm animals to live in the property...goats, chickens, poo, and pee everywhere! The stench was unbearable, lots of damage and everything from the floor up to 4' needed gutting/replacing, plus a redesign of kitchen and baths. The house is a diamond in the rough, sits on 5 acres, close to our daughter and two grandkids, and priced well below market value. It is a dream home for us and really suits our lifestyle. We hope to decide on the floorplan while homebound in CO so that once we get to TX, we can move ahead with construction. @millworkman - spiral stairs can be a pain for sure! Yet not a dealbreaker for us. Whoever had this custom house built seemed thoughtful of that specific stair. Downstairs, there is a living room, an open space for dining and kitchenette, laundry, office, and a jack and jill bath with two separate toilets and sinks. For us empty nesters, it's a great floorplan. Our grandkids will have the lower level to themselves when they visit. There will be a washer and dryer added to the master bath, so no lugging laundry up and down those stairs! @Patricia Colwell Consulting, we have a construction loan in place, ready to go, and have allocated more than enough to cover the entire reno. My husband and I have years of experience working on houses with an understanding of expenses, so budgeted accordingly. We drove to TX for closing - right before the virus hit full force and impacted the U.S. We brought our tools with plans to stay a few weeks to demo, meet with contractors and an architect, yet got word of our post lockdown and had to get back to CO quickly, leaving many loose ends. Wanting to move things along and to help family, we've hired our son in law to demo what's definitely not staying and to meet with contractors. He's a muscular guy, is loving the work. Plus is surprising us with his quickness! I'm a home stager by trade @ANNARTHUR HOMES | Home Staging + Design, and we've reworked rooms before, yet adding a bath to this situation is a challenge, and we felt it'd be money well spent to hire an architect. He talked with us while visiting the property...went over our wishes and design ideas in great detail. We received the rough floorplan, and we're working on tweaking particulars with him. Meanwhile, my hope is another professional will see the floorplan and share ideas on how to best to work in a guest bath and redesign the kitchen layout. Thank you all. Very grateful for advice

The Cook's Kitchen: I just re-read your comment. Yes, we would put our kiddos upstairs and convert their rooms into an apartment with a separate entrance. There is already a bathroom that just needs to be converted. We definitely want to make this long-term friendly for him, expecting a wheel chair down the road. We will look into the selling both homes idea... I see that as being more complicated, honestly, since buying a larger home would be contingent on the sale of 2 homes.... There are currently only 6 homes (that meet price and size) for sale in our desired area...