It didn’t get a whole lot of comments or upvotes, but the original post is here.
Basically, in winter, the first floor is way too cold, and the third floor is way too hot. I thought this was due to thermodynamics – my house is taller than it is wide, so there’s a sort of stacking effect going on. I figured the geometry of the house just lent itself well to directing heat in all the wrong places, and the fact that there’s three zones (one for each floor) would only barely mitigate the effect.
I was completely wrong.
I got an HVAC guy over and he took a look at the system, and what we found was hilariously wrong. Basically, these two vents on the second floor in my living room weren’t connected to any zone. They were completely bypassing all dampers. So when the first floor heat was on, those vents were blowing out hot air. As an experiment, I completely sealed them off with paper and painter’s tape, and lo and behold, the first floor could stay at a pleasant 70 degrees and the third floor would stay around 73.
Today the HVAC guy came over again to install a damper specifically for those two vents and connected them to the third floor zone. Now they only turn on when the third floor’s thermostat is turned on.
Never blame the laws of physics that which can easily be blamed on a builder’s error! Looking forward to not simultaneously freezing and sweating next winter.