Rheem 14AJM30 with RHBL-FR36T air handler gets the tax credit. AH uses X13 fixed speed high efficiency motor. It is 21" deep, 24" wide, 36" high. Air comes in front or bottom.

Here's the thing you have to remember about relative humidity: when you cool air, relative humidity goes up. Yeah, air conditioners reduce humidity, but they do it by dropping the air to below its dew point, at which time the humidity condenses out of the air and becomes that condensation that drains away. The air emerging from the vents on your a/c unit is darn close to 100 percent relative humidity for its temperature, maybe 55-60 F or whatever. The lowering of relative humidity comes as a result of this newly-cooled air mixing with warmer room air and having its temperature go up. The other way to dehumidify air is simply to heat it. That's why the relative humidity goes down in the afternoon and you see those 90 - 100 percent relative humidity readings early in the morning when the temperature is at the day's lowest. This is also why a dehumidifier first cools the air to below its dew point and then warms it back up by routing the air first through the evaporator then its condenser. If you only cool the air (and then throw the heat away outdoors, as an a/c unit does) you're only able to dehumidify to the extent that you can continue to cool the air. You take a cool damp basement that's only maybe in the mid-60s to 70 temperature-wise, start running an air conditioner there that's getting rid of heat, and pretty soon you can't remove anymore moisture because your air temperature is getting colder (naturally increasing the relative humidity). And, the air emerging from the a/c is now only a few degrees cooler than the air going in, so there isn't much moisture being removed there either. This same thing occurs if it's a damp day and you run a/c to dehumidify the house. Because you're only cooling the air, it can only be dehumidified to the extent that it, a) needs to be cooled, and b) can increase in temperature after emerging from the a/c system. The bottom line is that precise control of indoor relative humidity is hard with normal mechanical equipment that's available to consumers. But here are a few things to keep in mind: First, a dehumidifier is good only where you can use some heat. They're going to add to the air an amount of heat exactly equal to the power they use, so if you buy a 900-way dehumidifier it's going to add about 3,000 btu of heat to your space. Do you want that heat? If you're also running air conditioning probably not. In cool, weather, or in a place that's normally damp such as a basement, yes - the heat is wanted and it also helps dehumidify. Second, the best way to control humidity with air conditioning systems is with low-capacity equipment running a high percent of the time. You can do this with a variable-capacity compressor, or if you want to do it on the cheap you can supplement your central a/c with a 5,000 btu window unit running constantly. (Combined with raising the thermostat setting of the main system so the window unit does more of the cooling, especially at high-humidity, lower-temperature times such as nights and rainy days.) The key is, keep removing moisture while cooling less.

Table 402.1.2 from IECC 2015 to current is best prescriptive guideline for cost effective energy efficiency. I doubt using weaker local amendments is good strategy. Some energy efficiency experts feel that R49 is good minimum for ceilings in ALL climates and would agree, if the ceiling is traditional vented attic where thick layers of insulation are easy to apply and affordable (loose fill). Some high performance projects in cold climates approach R100 for ceiling. These are international code minimum prescriptive numbers and it's easy to use other compliance paths to demonstrate equal total performance through other balancing improvements. Renovations of vaulted ceilings and insulative sheathing above the roof deck can make sense to go with weaker values. Spray foam applied to bottom of roof decks usually have substantial thermal bridging through rafters or truss chords, often more than the vented attics that prescriptions are based on so I don't think they deserve much leeway. Martin Holladay has the classic article on this common code violation. Efficient homes heating with mini-splits don't need heads in every room, but will need their doors open during hot or cold weather, a deal breaker for many. Then there is David's point about resale but I think good implementation could help tamp down this possible sentiment. Haven't built ductless yet but open to it if owners are. The efficiency one gets with Mitsubishi's smallest unit is unbelievable. One head replaced a whole house furnace in my personal small home, granted winter design temps are stretching it. Energy Star is for all homes. Homeowners or owner builders are eligible but may have a steeper learning curve to get the right details. Always involve a rater early, preferably with feedback during the design stage. Cpartist, sorry for your trouble. With everything you have had to put up with, it's not surprising they flubbed an important technical detail of your build. I think people who value efficiency have to do extra research to ensure they are getting the right feedback on their design and selections. The architect or builder should have the right knowledge and experience in your goals and I think the best projects are collaborative from the beginning. Most build teams valuing efficiency still include HERS raters (Energy Star) and mechanical engineers specializing in HVAC for services like Manual J, D, and S. Third party diagnostics, commissioning, and verification usually help ensure a good investment in home performance certifications like Energy Star.

No room for duct work. The HVAC pro said I just had to lower the ceiling in one small area of the hallway and the duct work would come right off the horizontal fan coil and service all the rooms. The duplex is in South Florida. Very little need for heat.