Sarah wants to add ductwork to her 3.5-ton HVAC system to heat and cool a newly enclosed garage, expanding her home from 1,027 to 1,227 square feet. Derek Cole warns the unit is likely oversized for the original space, and two or three new runs may not deliver enough airflow to a room with three exterior walls. He recommends a load calculation and duct redesign before proceeding.
I have a question. My home is only 1,027 square feet with a 3.5-ton unit. We are enclosing a 1-car garage, which will make it 1,227 square feet. The garage is on the side of the house where the sun sets. We wanted to add 2 to 3 airways to add airflow into the garage that is insulated. Would this be a problem or a concern?
Hey Sarah, thank you for the question. A couple things, you're going from 1027 to 1227, which is, you know, you're adding 200 square feet. A 3.5-ton unit, that comes up to about 350 square feet a ton, which sounds a little large to me. Sounds like too much of a unit, but you really won't know unless you do a load analysis on the home. It's gonna You know, things are going to factor into it— insulation in the walls, in the ceiling, in the floor, uh, windows, what kind of windows, where the windows at, northeast, southwest. Um, but it sounds like a little bit of a— too— that unit's too big, um, because right now it's sitting on 1,027 square feet, which is, uh, really Sounds big. So a couple concerns is that, is the unit sized properly, and do you have a duct system that can handle a 3.5-ton? Uh, probably with that square footage you don't have a unit, uh, duct system that handles that unit. Um, so tapping into, tapping into it with 2 runs is going to be a challenge because you're taking away from the main home and you're adding a room to it which has 3 outside walls, right? You can run that garage and trying to condition it has 3 outside walls and trying to condition that, that space with 2 runs from the existing duct system. So, uh, that could also be a concern. Um, that room is probably a challenge to keep comfortable. And then it might also affect the whole home in the comfort because you're tapping to— you're tapping to an existing system. So that room's not going to be comfortable, and then the whole home in turn is not going to be comfortable because now you're, you know, putting, you know, 200 to 400 CFM of air that was once in the home to that extra room that you're adding on to it. So a couple things to check. Um, love the question, appreciate the question. Uh, a few things need to be done. Need to do a load analysis to see what the actual home needs with that room added to it, and is that duct system big enough for that 3.5-ton? It sounds like the units too big. But again, you know, something I wouldn't know for sure until you do a load analysis on that home with the new room to see what needs to be done. I think once you do that, you'll see it's probably a little different, and then you can size the duct system and airflow and make this system be designed for that home and actually be comfortable.
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