Do I need to increase my HVAC trunk line size?

Question

I'm thinking of finishing my basement. I currently have a main trunk coming off my furnace that measures 20" wide by 6" tall. I'm trying to future proof my home in the event my current furnace can't keep up with my heating needs. I have a number of options:

1. Add a second furnace. (I don't like this idea because it will eat up a lot of ceiling space running more ducts)

2. Upgrading my current furnace to meet the needs of the additional SQFT. (My current furnace is only a couple years old. I've been told by a couple contractors that it's just barely under powered for the SQFT in the total house, so I'm leaning away from this to avoid the cost of replacing my current furnace.)

3. Upgrade my main trunk to accommodate a bigger furnace in the future. This way I don't have to tear my ceiling apart if I decide I need a new furnace. This is where my question lies, do I really need to upgrade my trunk to a 24" by 6" which is what the contractor recommended?

4. Do nothing and hope for the best? (With my current furnace being "just under powered" for my SQFT, my plan is to put a nice fire place in the basement to hopefully pick up the slack.

I'm looking for advice on any of my options.

Answer 1

I'd go with option 4 to begin with. I'd recommend it for a number of reasons:

• It's a separate unit, so will act as a separate zone in your house, meaning you don't need to run it when no one is down there (saving you money).

• modern direct-vent gas fireplaces with built in circulating fans are quite efficient and pretty much act as a furnace...especially if you get one with a thermostat remote (as we did).

• fireplaces look nice (especially in a basement, where it can get especially dark during the winter months). A nice gas fireplace can certainly be a selling point.

• for the reasons you mention (no need to run new ductwork, no need to replace the existing furnace, etc.)

We have hot-water baseboard heat, so thought that running an entire new circuit in the basement, while nice, would be a challenge and expensive. We felt we might eventually need it (given that we went with bare, stained concrete as the floor) but thought we'd try a fireplace first.

We installed a direct-vent gas insert (we had an old wood fireplace already) with a built in fan. We also added a ceiling fan to the main room when we finished the basement.

When we want to use the basement in January (we're in MN) we just turn on the fireplace and ceiling fan for maybe 10 minutes and the place warms REALLY fast...even the concrete slab. It works amazingly well. Granted, it will all depend on the size and layout of your basement.

For the most part, we just use it when we are down there (it's the family room, so after dinner TV and the like). If we know it's going to be especially cold for a few weeks, we set the thermostat remote and let it cycle by itself on and off.