One of the biggest reasons the upstairs gets so hot is that the current sealing, insulation, and ventilation systems are not working correctly. On the sealing side of things, gaps in the home's structure can go unnoticed and quickly add up, causing air conditioning to be wasted.
Unless your roof is blocked by the sun or deflects rays, hot air will penetrate your home and heat your attic. As the hot air travels through attic space, your second floor will also absorb the heat, making it difficult to cool down.
Cooler air settles into the lower areas of the house (usually where the thermostat is located); while heat from the outside begins to warm things up again. Because heat rises, the temperature on the second floor rises first, causing the second floor to feel warmer than the first floor.
Cold air is denser than warm air so it stays on the bottom while warm air rises. That's why the downstairs can feel so chilly while the upstairs is toasty in the winter.
Blame physics: hot air rises while cold air sinks. That means your upstairs typically gets hotter than your lower levels, even if your air conditioner's working in overdrive. Your roof's hot, too: Unless you have shady tree cover, your roof absorbs a ton of heat from the sun.
When hot air rises, upstairs rooms become hotter. A hot roof due to the heat from the sun: Since your upstairs ceilings are so close to the roof or the attic, they are bound to be hotter than the downstairs ceilings.
Two units allow for an easier time balancing the desired temperature in your home. Generally, one area of your home will be warmer or more difficult to cool than another. In a two-story home, the upstairs area is often warmer, as warm air rises. Having two AC units in your home can help balance out the temperature.
Yes, in most cases you could benefit from an attic fan. Attic fans pull the hot air out of the attic and ultimately lower the temperature inside.
If you have a top/bottom return vent setup, close the top vents in the winter months. Closing the top vents will make your system draw in air from the bottom vents that are at the low point in the room where cold air settles.
Here's what you do: set your upstairs thermostat to your desired temperature goals, and then set your downstairs unit to be two degrees warmer. For most homes, this naturally encourages a temperature balance that's comfortable and right at your desired temperature goals.
Though there can be a bit of wiggle room, generally speaking, you should have your air conditioner serviced twice yearly: once in the fall and once in the spring. This is to ensure that it's clean, that its parts are in good shape and that it's operating as optimally as possible.
Air leaks and poor insulation are a common cause for making your house feel hot, even when the AC is working, as they can allow the air your air conditioner has worked so hard to cool to escape, leaving your house hot. Humidity can interfere with your thermostat's ability to track temperatures and also traps heat.
The design of Britain's buildings
This coupled with heavy insulation means they are excellent at trapping heat to help residents stay warm during the winter. But after a few sunny days, British homes become 'heat islands' – an area that is significantly warmer than its surroundings.
Clogged Air Ducts
If a blockage occurs somewhere within your ductwork, you can count on it affecting the airflow to some part of your home. If a clog is blocking the ductwork connected to a particular room, the air meant for that room could end up being sent somewhere else, resulting in uneven temperatures.
Even if you have a central air conditioner in perfect condition, your upstairs will need much more cooling than the main floor for the temperatures to feel consistent. Here's the point: Rooms upstairs are much more exposed to the elements than rooms on the main floor.
The general rule of thumb for a two-story home is that you should set each thermostat two degrees Fahrenheit apart from the other. During the summer, when your AC is running, set the upper floor at the temperature you actually want in your home. Then set each floor underneath that to two degrees warmer.
Your sleeping environment and the bedding you sleep on are the most common reasons people get so hot when they sleep. This is because your core temperature drops a couple of degrees during the night and sheds heat into your surrounding environment.