I'm familiar with the stack effect whereby heated indoor air rises up towards the ceiling and out. But, I seem to have the reverse happening where air is rushing into my basement; a reverse stack effect, if you will.
Anyone heard of this, suffer from this, have a solution for this????
Thanks
If air rushes out somewhere in your home, air has to rush in somewhere else. You need to find the air leaks and block them, just don't block vents for the attic or air supplies to combustion sources like furnaces or fireplaces. BTW fireplaces are common sources for pulling the air out and often the replacement enters in the basement. If you have a fireplace don't block too much as you MUST allow fresh air in for safety.
When air is leaking from above the basement, the lower cooler basement is where the air is replaced.
I agree wit Mr Meehan & SQLLit. You are describing the supply end of the stack effect. TB
I realized after reading my post and answers that I had to clarify something: the air is not coming in from walls, windows etc in my basement. What I am referring to is air moving down, into my basement from the first and second floors. When I stand at the door to my basement, air flow is moving down, into the basement. The only appliances I have there are my direct vent furnace (which draws air from the outside for combustion) and my water heater (which uses inside air for combustion but power vents to the outside).
Any comments?
Yes, the air coming down is cooler air. Therefore, warmer air is going up (or out) at the same rate.
The cooler air may feel like it is moving at a high rate, thus the stack effect, but an equal volume must be moving in the opposite direction. Could be going up a stair well or other openings, but it is a law of physics. The cooler air is in a smaller space and has higher velocity, the warmer air is either in a larger area(s) and thus has a lower velocity for the same volume. Or it is in an area that you just do not feel it.
Light a candle. Move the candle about and watch the flame. Stand in the doorway and see if the flame moves in one direction at the bottom, the other direction at the top. This is very common. Try it near outside doors and windows
Some air may be moving out from the water heater vent, that would draw air in from some place. Could be a series of tiny leaks, such as wall switches and receptacle boxes on outside wall, openings to the attic, window leaks, door gaskets, etc. Does the furnace have return vents? Are they working properly? If not, the furnace will draw in air from any place it can, like the stairwell.
Someone who understands the stack effect.
You aren't replacing air that's sucked out at the top. Cooler air comes in at the bottom, forcing the warm air out at the top. The warm air is being blown out the top by the cooler air entering below.
In order for warm air to rise, the not-quite-as-warm air already there needs to go somewhere else. As the air in the room cools it will sink; right down the stairs. This will reverse in the summer.
In the winter I hang a curtain (cloth shower curtain) at the bottom of the stairs on a spring-tensioned rod. I put it as close to the ceiling as I can so the warmed air from the wall heater in the rec room doesn't rush up the stairwell. Come May, I move the rod to the top of the stairs, hung low so the curtain is at floor level so the cooled A/C air doesn't rush down the stairs.
While this is obviously not as effective as an actual door in the stair well, I believe it should help my utility bill. Or I could just be kidding myself.
Normally, I'd blame the furnace. which is either requiring more combustion air than you basement can easily supply, or is sucking up basement air and feeding it through your house. But it could also be an unused chimney stack, or any of a number of other things.
Blow some smoke in the basement, and follow it to see where all the air that's rushing down the stairs is going. depending on the answer to that, either block the exit, or supply it with air from somewhere else.
-Goedjn
Your house is probably fairly loose in air exchanges. A blower door test would pinpoint all locations of air infiltration and give you your present rating and what to try to achieve. The 2-300 for the test will be well spent saving you also in the cooling serason. I had one and found leaks where I never would have looked otherwise.
Hey Mark
I did have the blower test done and my house rated very well (around 75 I believe). The only thing he recommended was a heat recovery ventilator because the house wasn't allowing enough air changes. I did have major leaking from the main floor fireplace wall (air leaking in between drywall and brick, mantle and brick, etc. I shut up the damper with caulking and a plywood plug and had the chimney capped. But that doesn't help me with the air flow down to the basement.
Thanks for the candle test Edwin. I'm going to do that as soon as I'm finished here. I did install two returns in the basement when I remodelled so that shouldn't be a problem. Also, the furnace is a direct vent so it should draw all it needs from outside, no?
That is something I'm going to try for sure. However, as I mentioned, it is a direct vent furnace which draws combustion air in from outside. Shouldn't it take in what it needs? Also, this is not a new problem: I had this same air flow with my original furnace.
Edwin
I did the candle test and it showed flow down the stairs to the basement all the way from top of the door to the floor. No flow is coming up the stairs. I have to believe that something weird is going on...
Now comes the difficult part; finding the opposite. . It has to be going up someplace. Check the ducts when the furnace is not running and see if you are still getting flow.
Are you getting the effect only when the furnace is on, or all the time.
If its just when the furnace is on, you may have an open return in the basement that is sucking air. Check al lthe return ducts and see if there is not one with a perhaps hidden opening. We had this in our house, it would suck the basment door closed when the blower came on. I closed up the open return and problem solved.
I don't thin k it is a good idea to have an open return duct in the basement.
Mark
"Are you getting the effect only when the furnace is on, or all the time.
If its just when the furnace is on, you may have an open return in the basement that is sucking air. Check al lthe return ducts and see if there is not one with a perhaps hidden opening. We had this in our house, it would suck the basment door closed when the blower came on. I closed up the open return and problem solved.
I don't thin k it is a good idea to have an open return duct in the basement.
Mark "
I agree, this is a common problem. The way returns are run, a lot of them have substantial leakage and it's not uncommon to feel pressure on a basement door while the blower is running. I'd start there. Try just turning the blower on/off, not the burner, and see what happens.
Just a guess ,experiment, close the basement returns and supplys maybe some natural convection going on.
It of course happens only with the furnace off right. Does the furnace intake and exaust direct through the wall, you have no old chimney that could be drawing. Do you have a floor drain going to the sewer line that could have a dry trap, or an exterior sump through wall. You say your house it to tight, open an upstairs window to see if it stops.
Did Pella ever fix your problems, that online Pella lady never contacted me back.
Guys
I turned off the blower as a couple of you suggested and it did stop the flow going down the stairs.
Mark: the furnace does intake and exhaust directly outside. There is a drain but it is not dry (my furnace and humidifier drain into it). My chimney was capped off last year, so nothing is coming down it.
I do have two returns in my basement that I'm going to play with. It might be a balance problem?
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