DIY Disaster Doctor: In One Vent, Out the Other


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Alvin C. Miller of Hawkeye Home Inspections, LLC in Wellman, Iowa (via The Money Pit). Courtesy of the ASHI Reporter.

There’s no getting comfortable in this room any time of year, since the temperature-controlled air from the HVAC system enters the room from the supply vent — and escapes out of the neighboring return vent simultaneously!


This HVAC distribution design disaster is just like a dog chasing its tail. The room’s air supply vent (which pushes air into the room) is located on the floor, and the air return vent (which sucks air back into the HVAC system) is stationed just a few inches above it on the wall. As a result, all the warm or cool air meant to bring comfort simply leaves the room as soon as it comes in. This is the kind of poor system design that leads to uneven heating and cooling in a home, constant frustrations regarding comfort, and wasted energy and money.


In this particular example, one of the vents should be moved to another location in the room so that warm or cold air coming into the space has a chance to circulate before returning to the system to be warmed or cooled once again.

This isn’t just so that the room itself will feel comfier, which it will, but also because air needs to move through the system several times before it reaches the temperature you’ve set the thermostat to; in other words, the air isn’t going to be instantly hot or cold when you flip the switch.

This air circulation challenge is unique to forced-air systems, and can actually be more of a problem in newer homes than in old. Older homes usually have a supply and return vent in each room (though not usually in the goofy arrangement seen here), which makes for pretty effective, reliable air delivery and climate control. Newer homes, on the other hand, have supply vents in each room but the return vent is usually centralized in a hallway to serve a collection of rooms or entire wing of a home. So that means that, even with the door closed, air has to be able to leave a room and reach that return vent; this is usually accomplished by undercutting interior doors by at least an inch to facilitate the process.

There are several adjustments you can make if you’re noticing uneven air delivery in one or more rooms in your home. For starters, make sure supply and return vents aren’t blocked by furnishings, window coverings or other décor. If there are rooms you aren’t using that don’t need comfort control, you can essentially remove them from the airflow circuit and reroute the conditioned air to other areas that need it by strategically turning off the supply ducts and sealing them with a piece of plastic behind the vent grille. You can also install duct dampers, handy in-line controls that use baffle action for open/closed control. Basic HVAC maintenance also helps identify issues that reduce air flow, driving up both heating and cooling costs.

To help locate air flow issues, use the tissue test. With your HVAC system running, hold a tissue up to supply and return vents; if they’re working properly, supply vents should blow the tissue toward you and return vents should suck that tissue away from you into their grilles. From there, solutions can range from duct cleaning and re-sealing to HVAC system design tune-ups by a qualified pro. Just don’t hire the guy who installed the over-circulating vent setup we’ve been looking at here!

Skill Level?
It depends on the extent of the solution. Initial diagnosis and slight adjustments, like duct shutoffs, are DIY-able. But bring in a pro for system redesigns and installations.

Tom Kraeutler delivers home improvement tips and ideas each week as host of The Money Pit Home Improvement Show, a nationally syndicated radio program. He is also author of My Home, My Money Pit: Your Guide to Every Home Improvement Adventure. You can also subscribe to Tom’s latest home improvement podcast or free home improvement newsletter.

** Got a DIY disaster you’d like us to feature? Send a photo of the disaster to, and we just might publish it here on DIY Life. All submissions will remain anonymous. **

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