Negative Pressure

The finished basement room where we stay at Heidi's mom's house is usually pretty comfortable. A space heater makes it cozy enough in the winter, and one of those portable air conditioners is usually all it takes to keep the place cool in the summer. Unfortunately, the days of unprecedented heat this summer have strained that setup to the verge of discomfort.

At first, I thought that simply giving the a/c a chance to run would cool the room down, but nope. Then we wondered if the unit was running properly, but it was. A quick calculation showed it was appropriately rated for the size of the space, so that wasn't the problem, and there was a separate dehumidifier as well, so the moisture wasn't overwhelming its function, either. 

Here in Buffalo, central air has only recently been added to most residential construction, and houses like this one, built in the 1960s, have piecemeal solutions to the rising temperatures we have experienced over the last few decades. Heidi's mom has a mini-split unit in the family room (that theoretically reaches the kitchen) and a bigger one for the second-floor bedrooms. That leaves the living room, dining room, and office without cooling, but those spaces just aren't used if it's too warm.

I think I've figured out the problem, though. The mini-split doesn't reach the kitchen, and they don't have screens in the windows. That means that heat has built up in the rooms that aren't air-conditioned, making them sweltering and stuffy. When it's running, the little a/c we have in the basement vents air continuously out through a duct hose. But what is happening is that negative pressure from that venting is drawing all the hot air down here from the rooms above us through the floor. 

It's counterintuitive, but the fix is to open the upstairs windows and maybe even run a fan to push air out that way. But nobody wants to "let any more heat in," so we're stuck in a sticky basement.