Ductwork to nowhere
When I moved in, my house had a supply duct running to the garage. My best guess is that a previous owner wanted a conditioned garage and added it after the house was built. From reading this site, I know this is a bad idea, so I blocked it off at the register with some rigid foam blocking. The duct runs from the air handler in the basement, through a block wall into the crawlspace, and terminates at the garage, about 12-15 feet away.
Since this is now a duct to nowhere, it seems pointless to send air that way. Since it runs through an unconditioned crawl, that seems especially bad. Air pressure is low at supply registers farther from the air handler, so I’m wondering if this could help with that issue.
What effect would eliminating that stretch of ductwork have on the system overall? Any disadvantages to removing it?
Thanks!
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Replies
The concern is high static pressures leading to low flow and excessive supply temps. Put a digital meat thermometer or similar in the supply duct as close as you can to the furnace. The temp should be below 140F on most systems.
Removing and blocking the duct at its source likely makes the most sense. If the supply temps become too high, you will need to eliminate restrictions elsewhere in the system.
If you already have the vent blocked off and your system is running ok, then removing the ductwork won’t be a problem. If the garage vent was added to an existing system, that also indicates that it can be safely removed since the original system was designed without it anyway.
Make sure to restore the fire barrier where the duct penetrates the wall into the garage. You don’t want any air leakage between the garage and the living spaces, and you need at least 5/8” drywall as a fire barrier separating the garage from the rest of the house.
Anyone wanting a conditioned garage needs to use a separate system to heat and/or coil the garage. It is NOT permissible to share the home’s main system for this purpose!
Bill