When you turn on the central air conditioning in the summer, your expectation is probably that the whole home will cool off to a comfortable temperature. Thus, it can be pretty frustrating when some rooms stay hot and uncomfortable. You should not have to keep pushing that thermostat lower and lower to make these hot rooms bearable. Here's a look at four possible reasons why your home is cooling unevenly, and what you can do about it.
The vents are closed or blocked.
This is the simplest explanation and the easiest one to fix. Take a look at the vents in the rooms that don't cool well. Are they blocked by furniture, propped doors, or other items? If so, clear these items away to allow air to flow freely. Also, examine the vent itself closely. Make sure the lever is turned to the "open" position and that the metal shutters on the inside of the vent, which control air flow, are not stuck shut. Sometimes, the open/close levers can get stuck on older vents. If this is the case, you'll want to unscrew the vent from the wall and take it with you to a local home improvement store to find a properly sized replacement.
If your vents are opened and are not blocked, but you cannot feel any cold air flowing through them, then there might be a blockage in the duct leading to the vent. You'll need to call an HVAC professional to address this issue, since doing so requires special equipment.
There's no barrier between the levels of your home.
Are the rooms upstairs hot, while those downstairs are cool? If there is no door or other barrier separating the downstairs from the upstairs of your home, then this is likely the culprit. Hot air rises, so without a door or barrier keeping it from doing so, all of the warm air will end up in the upstairs of your home while the air downstairs stays cool. This is more of an issue in some floor plans than others.
Having a door installed to close off the staircase and separate the floors will help keep temperatures more even. An alternative is to keep the central fan running even when the air conditioner is not actively cooling. This will help keep the air circulating.
Some rooms are lacking insulation.
Insulation is not just important in the winter -- it also keeps the cold air inside during the summer. If some of your rooms are poorly insulated, they are likely to become warmer than rooms that are better insulated or found towards the interior of your home.
Take a look around the rooms that are staying too warm. Do they include overhangs? Are they next to a crawlspace, or do they have an opening to the attic within them? All of these areas are frequently under or un-insulated. Adding insulation will help keep the cool air inside, making the rooms more comfortable (and also lowering your air conditioning bills)!
Your blower unit is not turned up high enough.
Do the rooms that stay the warmest seem to be those that are located furthest from the air conditioning unit? One possible explanation is that the blower unit on your air conditioner is simply not turned up high enough for the cold air to reach the vents in these rooms. Take a look at the owner's manual, and turn the blower up a notch or two. Some blower units must be adjusted from the inside with a screwdriver, while others have dials on the exterior. If your has to be adjusted internally, make sure you turn the power off before making the adjustment.
If you cannot figure out why your air conditioner is not cooling evenly, contact your HVAC professional, someone like C B Lucas Heating & Air Conditioning. He or she can run some diagnostic tests to get to the bottom of the issue.