Why Does Hot Air Rise?
Hot air rises because when the air in your living space is heated, it expands. It then starts becoming less dense than the surrounding air. Just like a piece of wood will float on water since it's less dense than the water, less dense hot air floats into the denser cold air. This floating effect is known as a displacement force or buoyant force.
Ways Hot Air Travels
First, individuals often get confused between "heat rising" and "hot air" rising. Heat doesn't actually rise — it's the hot air that rises. There are several primary ways, however, that heat travels:
Thermal radiation often spreads out all around and not just up. For example, if you were to stand several steps back from a big campfire, most of the heat you receive is coming at you through thermal radiation. While the campfire's hot air does travel mostly upwards, it can still come sideways as well.
Heat that travels by conduction can also travel all around. Conducted heat often travels in the direction of the biggest temperature gradient as well as that with material with the greatest thermal conductivity. Conducted heat travels mostly to the coldest areas where it meets the least resistance.
Heat travels by convection may also move all around, however, it typically moves upwards and sideways. Hot air rising is a good example of heat convection. Air, when heated, often becomes less dense, causing it to be pushed upwards and sideways by more-dense, colder air around it that's being pulled down more strongly by gravity.
How a Whole House Fan Can Help Cool the Hot Upstairs
If you have a two-story home, you may struggle with a hot upper floor. But, you may not notice this temperature difference until the hot summer months. You maybe even tried to turn your AC unit up with the hopes it would help cool the second floor, but only to find it's still hotter than the lower level floor despite turning up the AC unit.
All day long, your roof is being heated by the sun, making it difficult to keep your house cool. And, while you may have your air conditioner on and it's working hard at fighting off the heat and humidity, it could benefit you from installing a whole house fan.
Whole house fans can also be used in moderate temperatures to help decrease your AC use, unless it's very hot outdoors. Whole house fans create a cool circulation by drawing in cooler outdoor air and filtering out the warm indoor air outdoors.
If you’re suffering from a hot second floor in your home, take a look at our selection of whole house fans. We’re happy to help answer any questions you have as well… just give us a call at 1.888.229.5757.