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What Is The Difference Between Convection And Drafts?

Last updated on 05/13/2022

What Causes Convection and Can I Stop It?

Anyone who's ever sat next to a window on a really cold day is sure to experience some chilly air movement. That air movement is sometimes the result of a draft, or air moving through the window. In other cases, it might not be a draft at all. Instead, it could be convection, and the two can be equally unpleasant. But what causes convection? And how can you stop it? Keep reading to learn more about this natural process affecting your home.

What is Convection?

At its core, convection is the process of warm air rising within a space or container while also pushing cold air downward. As the warm air that rises cools, and the cold air that sinks warms (presumably from a heat source such as solar energy or a furnace), the two switch places. This process will continue until all of the air within the space is the same temperature.

When it comes to windows, convection plays a huge role. A pane of window glass is the coldest part of a wall on a cold day, and as warm air from inside the space reaches that cold glass, convection occurs. The glass cools the air, the air drops, and new warm air supplied by the heating system replaces the warm air. This cycle continues again and again until the room and window reach the same temperature (which probably won't happen).

This cycle of air moving around the window can cause physically detectable air movement. Homeowners sitting next to windows will likely feel the air moving around them. A bare arm might even get goosebumps, as convection can potentially move a lot of air.

Convection vs. Draft

The air movement caused by convection around a window is often mistaken for a draft or leaky window. Even in homes with brand new windows with highly recommended air leakage ratings, homeowners might think that feeling of airflow might be a draft. And, while air movement from convection might be as uncomfortable as a draft, the two are not one and the same.

At this point, we understand that convection is caused by warm, heated air bumping into cold window glass and falling to the ground, and then being replaced with more warm air. Drafts are different. Drafts are the result of air movement making it through the window. These leaks can come in through old weather stripping, uninsulated gaps around the actual window frame, or spaces between the window panes at the meeting rail.

Warm air can escape through these gaps, while cold air seeps into the home. Some window drafts are so bad that curtains behind locked and shut windows might even move about on windy days.

Drafts are an issue, and they can account for much of a home's heat loss. In these cases, homeowners should consider replacing the windows with newer, more energy-efficient models. The contractor will install the new windows while also taking care of any potential gaps or drafty areas.

Convection is a natural process. While it can be unpleasant, convection has less of an effect on a heating bill than a drafty window. In this case, the cycle of moving air continues until the glass and air within the space reach like temperatures.

What You Can Do About Window Convection

While drafts are significantly larger issues than air movement caused by convection, it's still unpleasant to feel cold air moving by while watching TV or reading a book. Luckily, there are a few things that a homeowner can do to stop noticeable air movement caused by convection.

Encourage Neutral Glass Temperatures

One way to reduce the air movement caused by convection is to encourage neutral glass temperatures. Leaving curtains or blinds slightly ajar will allow warm air to reach the glass. At first, this will actually cause convection. But as the glass warms and equalizes with the air inside the space, the noticeable air movement will subside.

In areas where privacy or security is an issue, this is obviously not ideal. But, for homeowners that don't concern themselves with prying eyes, leaving curtains open can do the trick.

Promote Air Movement

Another method of mitigating convection's effects is to promote air movement through the space. Using a small fan placed by the window forces the falling air to mingle with the rising air, preventing the two from separating and causing a cycle of convection.

While this convection solution clearly increases air movement rather than reducing it, the moving air will be more comfortable and feel less drafty.

Clear Vents and Heaters

Most heating systems do a decent job of equalizing air temps within a home, if they're allowed to do their job properly. This means ensuring that any vents are clear, but also (and especially) return ducts aren't blocked.

Keeping vents and returns clear allows the system to cycle the warm air into the space while also pulling out the cold air back to the heating unit sooner. This will help equalize temperatures faster and reduce the felt effects of convection in front of a window.

Upgrade Your Windows

Ultimately, the best way to minimize the amount of air movement caused by convection is to replace your windows with more energy-efficient models. Double or triple-pane glass windows have small gaps between the panes, and those gaps are filled with gas. This creates a thermal break that makes it harder for colder temperatures from outside to bridge the gap and cool the inner pane of glass.

A Farmhouse with wooden front doors and restored windows

Also, in some cases, it might be worth looking into higher Solar Heat Gain Coefficient windows. In certain spaces, these windows will warm faster than a lower-rated window. This will hasten the time it takes for the air and windowpane temperatures to neutralize. Ultimately, this means reducing the amount of felt convection the homeowner will experience.

You Deserve a Comfortable Space

While it's true that convection is a naturally occurring phenomenon, that doesn't mean you have to live with it. With the explanation and tips above, it's possible to minimize the felt effects of the convection cycle, allowing you to enjoy your space air movement-free.

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