I plan on installing central heat and a/c to an old Jim walters home which is 2 story. I feel that I should have separate units for each floor, but an wobdering if this is cost effective. I am guessing that each level is about 1000 sq ft. The lower is well insulated , but the upper, we feel has very little. I hope to correct this but later this year. I have done no research on this yet, but I am wondering what size unit for each floor? I am in central Texas and I like my house cool. Also if anyone has recommendations as to a brand. I think that the ducts will have to be put in some kind of drop down area for downstairs and possibly the floor for upstairs as there is no attic. There is only about 1 inch between the roof and the ceiling at this time.( when I had the roof installed the roofing nails came through the ceiling.)

You need to have a manual J and a Manual D performed to determine exactly what size of equipment will be needed and what size any additional duct work will have to be. Get your insulation work done before the calculations are made.

Once these facts are known you can get accurate estimates done to reflect the true costs of heating and cooling your home. The estimates can be done so you can see the cost difference between one unit,one unit with two thermostats and a zone damper to allow separate control on both floors of the home OR my preferred solution which is two complete separate systems.

Brands are all about the same. They all heat and cool it depends upon how fancy you want the equipment to be and how long the warranty lasts.

The most important thing is the install. A poor instillation can take the most expensive equipment and turn it to junk in short order. The cheapest equipment installed properly will last for many years. Check with the BBB and your neighbors and friends to see who has made them happy with there furnace and A/C work. Stay far away from any company that will not do a Manual J and D for your job. There might be a extra charge for the Jand D work but it will be worth every dollar and more. Your comfort and energy usage is of prime importance especially since the utilitys are so expensive.