Q - I am in the process of getting a new heating and air conditioning unit installed in my 3-story home.  I just had an estimate and the company recommended a single 5-ton unit.  Does that sound like enough tonnage to you?

Rick - Lawrenceville

A - For my money, no single unit sounds like enough muscle for a 3-story house.

Even with electronic dampening I don’t think you will be happy with a single unit servicing your entire indoor area.

If it were me, I would seriously look into getting at least two units, if not three units for your house.  I think a good rule of thumb is a unit per level, but you need to look into at least 2 units.

If you go with two units, you would want to put the upstairs on its own unit because upstairs will generally always be too hot in the summer.  It will be good to have the upstairs on its own thermostat.  Then you can tie in the middle floor and the lower floor with the other unit.

Before we go on I suppose we need to call a timeout here. Is this truly a three-story house, or are we looking at two floors and a basement?

I’m asking because if it is two floors and a basement, I would really be more inclined to push getting three units.  I think a basement, even if it is a walk out basement, will have different load demands than a regular inhabited floor and I think you will be much happier and much more comfortable with three systems.

Your next step is to get a qualified HVAC company, or two, out to your house, (and I am now going to assume that the first company you had out is not qualified because all they recommended was a 5-ton single unit).  A qualified HVAC company will look at all aspects of your house including shade, windows, insulation, and direct sunlight before making a recommendation.

(If your top floor is just a room over the garage you may want a system on the lowest level, a system on the middle level, and a mini-split system at the top).

While it may be a little costlier up front, you will be way way way way way happier (and healthier) with an extra system or two.