I have central air in my house(20 year old house). In my basement it gets cool, and cold air is coming from a vent in the ceiling. My upstairs gets really warm and humid even though central air is on. What should I do to resolve this? I was suggested to replace windows, fill attic/crawl space. I heard there could be a tool to help even out the air but the technician wouldn't share the secret.
George Anderson is right. Balancing air flow is the easiest and most cost effective solution. Obviously, cold air is heavier than warm air. In the summer you need to direct AC air flow to higher floors and restrict it on lower floors. In the winter you reverse this directing heat to the downstairs and letting it rise via convection to upper floors.
Ceiling fans also help if used properly. To cool use mid to high speeds blowing down in the summer. In winter use slow speeds blowing up in order to bring warm sir from the ceiling down the walls.
Is there sun shining on the upstairs moreso than the basement? It sounds like part of your problem could be solar gain. The sun applies 1000 watts per square metre (about 100 watts per square foot, or 300 BTU/sf), almost all of it turns into heat. A light colored wall or roof will reject some of that, the lighter the better - my preferred white paint has 91% albedo (reflection of solar energy).
So most of your A/C capacity is going to reject that “solar gain”. However, solar gain falls only on parts of the house, and this changes through the day. In the morning, your east-facing rooms take the brunt (but they’re usually cool from the night before, so not much of a factor). In the afternoon, south and west facing rooms take the brunt. If clouds roll over, solar gain is reduced, and now the house is being heated evenly by the outside air which is warm.
Let me guess, you’re trying to counter that with a “1-zone” system. That is, the system cools all rooms equally, and is not mechanically able to redirect the cooling to where it is needed most. Further, I bet that same system is used to distribute heating. Heat turns the formula upside-down, because now, “solar gain” is your friend! The solar-gain rooms require less heating than the rest of your house, and may get too much heat.
So how do you want your system balanced?
- Afternoon sun during A/C
- Evenly, ignoring all solar load
- Afternoon sun during heating
Whatever choice you make, you’ll have to adjust registers to accommodate that choice, and then, you have to live with it. That’s what a 1-zone system means. This is why multi-zones are becoming popular, particularly with “mini-split heat pumps” which both air condition and cool.
It’s also possible you could use any adjustment features on the registers to adjust it “on the fly” hour by hour, but then you’ll a) need to have a strong grasp of the problem, and b) go around and do it all the time.
Another, simpler option is to install a window A/C on the room in question.