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Let's face it, when it's hot and you don't have air conditioning it can be borderline homicidal. What's worse is when the temperature begins to dip outside and your home feels like an oven. Most of us turn on a fan to get some air moving across our skin - which is a great idea.

But moving hot air around feels pretty futile, doesn't it?

What if you could replace the air in your house with new, cooler air, quickly and efficiently? You can! All you need is a fan and a cooling plan.

When I was a volunteer firefighter we had to replace the air in people's homes all the time. We would get called to a home because someone forgot to take the bread from the oven and the smoke emanating from the stove would begin to fill the entire home.

Often time we could completely exchange the air in a house with one fan in just a few minutes by using Positive Pressure Ventilation (PPV) or Negative Pressure Ventilation (NPV), depending on the situation.

Here's how it works.

If a home is full of smoke, all of the windows would be opened and a fan would be placed about 6' from the front door on the exterior of the house. The air blowing into the house would increase air pressure and force the smoke out of the rooms.

Conversely, if the smoke was localized then we would place the fan about 6' from the door on the inside of the house facing out, thus creating a negative pressure in the house. This would cause air to rush into the open windows throughout the house, pushing the smoke out the front door.

Granted, we used a fan that had a wooden prop you might find on a small aircraft, powered by a 10 horsepower engine.

Don't despair! The principals of PPV and NPV can still work for you even if you have a regular box fan - it just takes some planning.

Spending all kinds of time and energy cooling your living room with a fan in the window does nothing for that EZ Bake Bedroom at the end of the hallway when it's time to hit the hay. What we really want to do with that futile fan is put it to work replacing the hot air in the bedroom before bedtime.

Step 1: Close Up The House

Yes, close all the doors and windows. Our goal is to systematically cool the house room by room and we need to seal off areas that don't need immediate cooling and provide a single place for cool air to enter the house. A box fan can only do so much so we want to be as effective with it as we can. Trying to empty the entire house with one box fan is a waste of time.

Would stacking two mini vornados work as well as stacking a box fan and a vornado as you described?
It will definitely help. The goal is to get about 50% to 75% of the opening you're pointing at to be filled with air from the fan. The other 25% to 50% will be air that is carried along by the low pressure created by the stream of fan-driven air passing through the opening. As I read this, I'm not sure I'm making good sense. I can see it in my head but the words are failing me.
<p>Absolutely fabulous instruction. It works!!! Thank you so very much for taking the time to share this.</p>
<p>Looks like a good idea. This lseems a bit like the same method Dyson use with their fans.</p>
we do the same with a small plastic 6 inch desk fan. place it on the windowsill next to an open window and it sucks cool fresh air in. much more effective than just blowing hot sweaty air around.
<p>Some 13 years ago I did a ~40 cm hole in the highest part of the attic's wall, and attached a cheap chinese box fan. In the heat summer evenings, I turn it on after the sunset, when the outer air is a bit cooler than the inner. It is very effective.</p>
<p>The fan is aiming to outdoors. The cool air enters through the windows or doors of the ground floor.</p>
<p>Good explanation of a simple concept that's not always obvious when trying to cool a hot house. It seems its almost counterintuitive until you think it through a little bit. Nice work!</p>
<p>True story. Closing up the house to cool it seems insane. It works really well though. Additionally, I hate listening to an A/C unit. Tis way, the fan is at the other end of the house and I still get a nice breeze coming through the window. A triple bonus... Cooler air, moving air and minimal noise. Thanks for the compliment. Sorry the drawings were so rough. I did this in a few airports while trying to get home from a business trip.</p>
<p>Thanks for explaining this process so well! I bet it works really great, and you're right there is nothing worse than a hot day with no air conditioning. Thanks for sharing!</p>

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