2 story house - central air unit. Cold air doesn't travel good enough to 2nd floor? what can it be?
Question:Already had all ducts proffessionally cleaned..Didn't help at all.
Answers:
the problem is that cold air is heavier than warm air and is harder to push to the higher vents..what is needed is dampers to control the amount of air feeding the downstairs vents as to the upstairs vents.you could partially close off some of your vents to force more upstairs...the best fix is to have return air vents installed upstairs(unless you plan to have a seperate unit put in for the upstairs) and dampers put in the system to cause more air movement up stairs...
Your cental air unit isn't large enough. I have a large home and I have two units. Gets like ice in here in a very short time.
Cold air sinks, so if your vents are floor registers then it will be very difficult to keep the cold air upstairs. The cold air just tumbles down the stairs. Try to keep your bedroom doors closed if possible. That will help to keep some of the air upstairs. Do you have a basement? I always close the vents in the basement during the summer since it's cool enough on its own. No need to push cold air into a cold space - better off to let the air go somewhere else where it's needed. Is your AC unit powerful enough for your house and is it working to specs? You may have to check with an HVAC specialist, or if you know what the model number is maybe you can find out what it's rated for on the manufacturer's web site..
you need to partially close some of the vents on the ground floor to get more air upstairs, the other part of the problem is that you are battling the laws of nature, since hot air rises and cold air sinks, hot air from downstairs is continually moving upstairs as cooler air sinks down to the ground floor.
When I had a 2 story I had a vornado fan on the ground floor blowing literally blowing air up the stair case, it helped keep the cooler air upstairs. hopefully you have an air intake on the upper floor to pull the warmest air into the AC unit. You may want to almost completely close the vent in the coldest room downstairs, chances are it will stay cool on it's own. Just don't close too many vents completely or you will reduce the overall cooling efficiency and make the blower work harder.
The other thing I did was put a sheet of plywood about 3' high across the upstairs hallway opening, like a sliding gate at the top of the stairs so it caused the cool air to pool behind it upstairs. like a dam or kiddie gate that was solid, if that makes it easier to understand.
most likely you ducts are not sized properly you can most likely solve the problem by shutting off the downstairs cooling vents this will force most of the cool air upstairs and since cool air travels to the lowest spot it can go it will also cool the down stairs (note do not shut off return air vents downstairs)also check outside unit if it is not free of dirt and grass wash it off with a hose. also look at the condenser in the furnce to see if it is dirty you can clean it with soft brush and change your air filter every month during the summer
Partially close the lower floor vents. This will increase the plenum pressure to force more air upstairs.
Cooling is all about circulation, so the first thing I would check is to make sure you have adequate return airflow from the upstairs. If you don't, nothing you do will fix this problem.
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