I was reading another post about cooling upstairs and downstairs efficiently. I had a few questions that I could not otherwise find the answer to.

I finished my basement recently, so all the HVAC lines are run, and there is a register in each room, and 2 in the family room. I have my Central air set to 75 upstairs, which my 2.5 ton, 10 SEER unit has a very difficult time with. The thing runs all day pretty much non-stop. My basement is about 15-20 degrees cooler.. with all the downstairs registers closed. I have one cold air return in the basement, and 3 upstairs - none are blocked.

Is there a way to add zoning with everything in place? I would love for the basement to be on a separate thermostat. I only have one furnace/ac unit. All the basement HVAC runs are attached to the main plenum for the whole house. With the finished basement my house is a 2680 sq ft. Rambler. I am sure that the 2.5 ton is way undersized, and probably an upgrade is in the very near future.

Thanks for the help.

Most registers have an internal set of louvers (on the duct side) for balancing. Some use an anemometer, some an infra-red thermometer for balancing. The idea is to open or close the louvers of each register according to the heat load of each zone, until a uniform climate is achieved. At that time, the registers are "balanced" and the thermostat can do its' job. It takes time while adjustments "settle", so be patient.

There is a "poor man's version of zoning" which will probably work in just that situation.

The idea is to not use full zoning, but rather just temper the downstairs a bit.

The basic idea is to use a motorized register damper for the basement register and an auto-changeover stat and a couple of relays to control just that damper.

The idea is that the basement would not cause the furnace or cooling to run, but would rather shut off the heating or cooling prematurely when the setpoint is reached.

So, there is a call for cool upstairs. System runs. When the basement is satisfied the register closes.

In heat mode, if there is a call for heat in the basement nothing happens unless there is a call for heat upstairs. Once there is a call for heat upstairs then the basement damper would open. The heat upstairs will likely turn off first.

I'm planning to do that in the laundry room because since installing an 96% efficient furnace, clothes hung on the line in winter don't dry.

This doesn't require a zoning panel.

Another application would be a kitchen. This may avoid an overly hot kitchen in the winter.

Zoning either requires motorized dampers in the ductwork or motorized register dampers and a zoning control panel.

The basement zoning would probably help you in the winter. For the summer, a door might help. Bifold, folding or regular.

Cutting off most of the returns might help too. But if you turn off too many a bypass damper may need to be installed.