Attic Ventilation - Hot Air Rises

Have you ever seen those colorful hot air balloons in the sky? Ever wondered how they really fly? No, it is not gas. . . it’s hot air, like their name, it is a hot air balloon.

The balloonist fills the balloon with air, then heats it with a propane burner. The air, when heated, changes its density and becomes buoyant, so when the hot air balloon reaches a warm enough temperature, it rises being surrounded by cooler air outside the balloon. The hot air balloon wants to lifts because it is lighter.

It is a basic scientific principle. Balloon air heated hotter than ambient outside air weighs less. Yes, a few grams per cubic foot less because the hot air has less moisture in it. The balloon can lift the difference in grams per cubic foot – until it equals the surrounding air temperature, then the balloonist needs to heat the air again to create more lift. I know a few grams per cubic foot is not much but when you have a balloon that is 120,000 – 200,000 cubic feet in volume, that adds up and can lift up to and over 1,000 pounds. That is why these balloons are very large, so they have lifting power.

So you ask: Why is Bob giving us a science lesson in hot air ballooning? I wanted to learn about attic ventilation. It is the same basic scientific principle. Hot air rises.

Like the Hot Air Balloon the trapped air in your attic when it gets hotter than the surrounding outside air, it wants to rise. I know what your thinking . . . . Is my hot air is going to lift my home off the ground? At only a few grams per 1 cubic foot that would never happen but the air still wants to rise and you can use this to evacuate this hot air out of the attic and replace it with cooler outside air.

The use of exhaust vents like whirlybirds, dormers and ridge vents naturally lets the hot airflow up and out as long as it gets replaced with cooler air from intake vents. These are normally near the bottom of the roof. This is a cost-effective and passive way to cool down the house in those hot summer months. Attic Ventilation will help cool your home from the heat. Ask your roofing contractor to calculate a balanced attic ventilation system for you. It will save you money using less us of your Air Conditioner.

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