Hey everyone, posting here hoping for some advice, or at least an explanation for what I'm experiencing.
I currently rent a 3 bedroom apartment in the north-eastern US. It's one half of a triplex, where I have the entire ground floor and basement, and the neighbors have the entire upstairs and attic. The building is brick, and I am fairly sure that there is no insulation between the brick and drywall. There's also lots of windows, some absurdly large, and none positioned in a good way to capture sunlight during the winter (but that's a different issue not related to this one). Let me preface by saying that I absolutely plan to move out of this place as soon as I can find a good deal on a house. I'm looking for a good deal on a duplex or triplex that I can use as both a primary residence and a rental property. Just waiting for the right deal to turn up.
In the meantime, I'm stuck trying my best to make the best out of my current living situation. Winters are dreadful, as the apartment is large with high ceilings and entirely heated by electric baseboard units. When I first moved in I paid $980 in one month to heat the damn place, because I was not prepared and had done nothing to winterize the place. At the time all of those windows were also single pane glass (I convinced the landlord to get those replaced with dual pane glass, and it helped tremendously). By sectioning off the apartment in the winter and heating only the areas actively being used, I pretty much cut the heating bill in half (which still comes out to about $400 a month, which is still terrible, hence my eagerness to move).
Cooling the place in the summer has always been much easier than heating it in the winter. I have a single 12,000 BTU window unit that can keep the entire place a cool 70 degrees if desired, while not pushing my electric bill above $200 most months. Still, I know that I should be able to do better, so I've been trying to make some changes to reduce my energy consumption. As per the advice given by MMM and others, I started turning off my AC at night and opening windows to vent hot air out and pull cool air in from outside. The trouble is, whenever I do this, the temperature inside my house will still reach about 80 degrees, despite the fact that the temperature outside is in the mid-high 60s!
For the life of me I can not wrap my head around how this is happening. When I turn the AC off around 8PM, the temperature inside the apartment is usually around 72 (this is crazy low, I know, but my girlfriend does not share my commitment to frugality and temperature acclimation and won't let me keep the place 80 all the time). By this time, the outside temperature is usually about the same, and continues dropping down into the 60s over the next few hours. So how is it that turning off my AC and opening a few windows (2 up high to let heat escape, 2 down low to bring cool air in) results in the inside temperature steadily rising to ~80 over the next couple hours? Where is this heat coming from? If the inside and outside both start at 72, how can the temperature possibly increase? Is it possible that the bricks that make up the outside of the house are retaining so much heat that they actually cause the temperature inside to rise at night despite all other factors?
I plan to be out of here before next winter, so this isn't anything more than a short term problem. I just want to try to understand what the hell is happening.
