Rectrangular 1680 square foot crawl space which is 5 feet high.I have two vents which have 110 cfi fans in each vent.I am thinking of getting two fans 220 cfi which will go into another vent locatied on the side of the crawl space. I dont know if that is going to be enough drawing power to do any good. One more thing is that the two fans (220 cfi)which are on a single humidstat.
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Re: humidity build up in crawl space
You have to get a constant flow of air through there to prevent that build-up. By the time the humidistat calls for the fans to come on you have already lost the game. you need plenty of venting on all four sides to kep the air moving and preventing buildup of humid air. the 2 fans of 220 each are sufficient, put place them apart so you draw air in from all the vents (at least 4 intake vents ) and provide for movement of the full crawlspace area air ---- that is the key for your sitation. Make sure you have enough vapor barrier over a good base of stone----4 mil plastic or heavier and about 3 inches of stone. All in all, check on what it would cost to have concrete poured, especially if you get a lot of cold air conditioned air seeping down from up above and causing condensation ptoblems.
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You can devide it up how you want. 675 squar feet is like having 675 one foot by one foot squars so a room that is 10 foot in one direction and 10 foot in another is 100 square feet so 6 of those would be 600 square feet and say a room that was 7.5 foot by 10 foot would be 75 foot
normall you will need one pint of water for each 1,000 cubic feed of space in your . . example. 2,000 square foot with 8 foot ceiling would contain some 16,000 cubic feet. = 16 pint per day capcity to dehumidify the area.
If the system is actually doing everything it can, which I do occasionally run into, then it's time to start looking at other factors like the heat loads. Number one problem I run into is either attic insulation or attic ventilation. One thing that really sticks out in your post though is the square footage and tonnage. Now, to be honest, what the square footage is from the home owner to actual living space always varies. Home owners always get the square footage like a realtor, but includes the garage and other unconditioned rooms. What your looking for is the square footage of only the rooms that have a vent. It is 400cfm per ton, 1 cfm per square foot. So if you have a 2.5 ton system, it is capable of doing 1000 square feet of living space. You said 1500 square feet, which would need a 3.5 to 4 ton system. Hope this helps and gets you to cooler days!
Depends on the cubic footage (length x width x height = cubic footage) and how damp it is. If you're not going to have to dump the collection tank (a drain hose is connected to the unit to run water out of the craw space and away from the house), I would run it on high for 24 hours and then lower it to medium for several days. After that, you should have a pretty good indication what it takes to keep the craw space dry. At least, until the next heavy, continuous rain storm.
If this is an on going problem, I'm not sure that a humidifier is the total answer. You need to look at the causes for this moisture (i.e) Are the downspouts carrying the water away from the house? Are the gutters and downspouts clogged with debris, causing the gutters to overflow? Does the earth around the foundation need to be regraded, so that water runs away from the foundation? Has the moisture barrier on the outside, underground around the foundation failed? Would installing an automatic sump pump in the crawl space be more efficient?
So, in addition to the dehumidifier, you need to look at the big picture and eliminate the cause(s).
YOu are asking a question that cannot be properly answered without knowing more of the situation. If this crawl space is subject to large air drafts and there are air vents that allow openess to this area, then you cannot be sure of the results. Since it will be winter, the humidity build-up is not so much a factor and you should take steps to isolate this area from air movement. Then you can apply heat. You may want to make a temporary plywood barrier around this area so your heat stays confined, thereby using the minimal heat needed to keep the temp you want. The heater will most likely handle the job; you should get a thermometer and keep the space at 40 degrees farenheit or slightly higher. When the warm weather arrives, remember to open the air venting again.