My gym had a dehumidifier in the group class room and it made a noticeable difference in how comfortable I felt when working out. It was a pretty standard sized one like you might get at Target. Nothing special. However, you would have to close off the room to have the dehumidifier actually lower the humidity in the room. If there is a breeze coming through, all the outside air will bring in new humidity and the dehumidifier won’t make a dent. In a gym that’s not an issue since the AC is also running to keep the room cool. Since a dehumidifier puts out heat when it’s working, I don’t think it would really make a sealed classroom comfortable since there is no external cooling. It might feel even hotter since there is not fresh air coming through.
This is actually how some places made cool air before AC. Put a block of ice in front of a fan. Even today, AC units are rated in terms of “tons”, which refers to “the cooling equivalent to X tons of ice”. You can do something similar in your class. If your school has a freezer in the teacher’s lounge, put a gallon or two of water in the freezer so it turns to ice. Then put them in front of a fan in your classroom. It won’t really cool the room much, but the air right in front of the fan will feel nice and cool. A typical classroom might need an AC with the equivalent of 1-2 tons of ice!
For times when you want cooling when outdoors, like camping, they make these coolers which blow air over ice. They’re good for small areas like the interior of a car or tent:
You probably wouldn’t need to cut your screens. Most or all of the portable air conditioners have a window kit that holds the exhaust hose in the window. The window is partially closed to hold the kit in place. The screen is not affected at all.
Here’s a handy BTU calculator. You can enter the size of the room and the number of people to find out how many BTUs would be needed. From that, you can look at the stand-up ACs and see what you would need.
If you would end up needing several ACs, keep in mind that they use a lot of electricity. You might not be able to use multiple in the room since it might be more than the fuses are rated for.
I’m a teacher in NYC, and was about to mention @Dewey_Finn ’ s point.
Are you sure your school would even allow you to run such a high voltage item? All the teachers in my school were forced to remove personal microwave ovens and/or small fridges from our rooms, because of power surges as well as higher electric bills. Having your own AC is strictly forbidden as well (teachers tried).
In our school only the second floor has window air conditioners. Those of us on the 1st or 3rd floor just suffer. It’s very dangerous during Summer School, so the parents in our district lobbied to hold July and August classes only in AC rooms.
Good luck! Teaching ain’t for sissies…
One thing to keep in mind with these units is that they are designed for home use where there’s only a couple of people in the room. In a classroom, there will be 25+ people, each of which is producing heat. You’d have to keep in mind that its efficiency would be affected by differences between a classroom and a room in a house.
One thing that would be cheap and easy to try is to get an actual window fan:
These fans are designed to go into the window frame and will effectively push air into the room. Put one in each window to greatly increase the amount of air flowing through the room. Keep in mind that the air coming in has to exit out of the room. Keep your room door cracked open so that air from the windows can flow out into the hallway. For even more airflow, put a fan in the doorway so it sucks air from your room and pushes it out into the hallway.
Another thing to try is to block the sun’s rays. If your windows face the sun, put up white poster board or something on the glass. This will help reflect some of the sun’s heat back outside instead of coming in the room.
I am not a heating/cooling engineer, but I remember my experience with trying to cool a 20ft X 25ft room, with only 2 occupants, in Los Angeles some years ago. Michigan wouldn’t get as hot, but I got the largest thru-the-wall unit available at the time (12,000 btu?) and it barely kept us cool. Unless they make larger standalone units now, I can’t imagine it would be of much use for a typical classroom with 30 occupants. And large units are quite expensive.
And IIRC, it was plugged into a dedicated, 240volt circuit, not something you will find in a typical classroom.
If I had wanted to get a bigger unit, I would have had to move up to a non-portable system like for a whole house.
I haven’t seen any, but I haven’t really looked into them much. The fan itself shouldn’t care about the orientation, but a horizontal unit would probably be tippy if it was turned on its side. It might fall down easily.
I’m assuming you have horizontal sliding windows. If you just want to try a quick experiment to see if the window fan helps, put the fan horizontally on the window sill and block off the area above the fan with poster board or whatever. If the window has blinds, pull them down so they are about at the top of the fan. This should give you a sense of what sort of airflow you could get in this setup. If it works well, then perhaps something a little more sturdy could be put together.
What is the job market like right now for teachers? If you went to your boss and told them your classroom conditions were unacceptable and you want a window air conditioner or you’re outa there, would they have to meet your demand?
The reason for blocking off the area above the fan is so that the air doesn’t just loop around in a big circle. The fan will push air out, but that air can loop around the open area at the top and go into the back of the fan. The fan would just be churning the air right around where the fan is. If you have blinds, have them come down just to the top edge of the fan so that they block off the top part. The bottom part with the fan would not have blinds covering it. That will help prevent the air from circulating around the top. And make sure there’s no open space on the sides of the fan for the same reason.
I would think the box fans would be a pretty good experiment for those window fans. The window fans may have a little more force and may work better, but I would think the box fans wouldn’t be too bad. One thing to make sure is that you have a way for the air to come into the room. If your box fans are pushing air out, you need an opening somewhere for new air to come into the room. Leaving your door cracked open may work for this. Or if you have windows on two sides, have fans on one side blowing into the room and fans on the other side blowing out. And keep in mind that the wind outside will also play a factor. If your fans are blowing air into the wind, the wind will push back and the fans won’t be very effective. You would want to orient your fans so that they push in the same direction with the wind to maximize airflow. That may mean that some days you have the fans blowing into the room and some days blowing out.
Before I managed to get some air conditioning into my bedroom, I’d lie awake at night fantasizing about this. You have to take the excess heat out of the room and put it somewhere. In this method, you carry it out as liquid water, which you have to replace by carrying in solid ice.
But it would work! You don’t have to cut any screens!
Now, how much ice do you need?
They sometimes measure air conditioner capacity in “tons”. This is, literally, the equivalent cooling capacity of a number of tons of ice consumed every 24 hours, to wit:
When I searched on “room air conditioner tons” (without quotes) the first hit said “Generally, in a comfort cooling setting, you can estimate one ton of cooling for every 500 square feet (assuming you have a standard 8-foot ceiling). In a more densely populated, cross ventilated area, we suggest one ton of cooling for every 250 square feet.” I think your densely populated classroom counts as “a more densely populated” area. So if your classroom is 20 by 25 feet, that’s two tons of ice per 24 hours, or about 1300 pounds of ice for an 8 hour day.