swamp cooler humidity levels

Asked July 16, 2014, 2:14 PM EDT

I've lived happily with swamp coolers since 1989. I understand that the cooling capacity is 10-20 degrees below the outside temperature, depending on both temp and humidity levels. But what is a normal in-house humidity level with a swamp cooler running? Mine has been running 60-85% humidity this summer (all summer, not just during rain) and it feels like Texas is living in my house. It's so humid that everything in the house, including me, is damp and sticky. I rent and my landlord needs convincing that there is really a fixable problem. Thanks for any help and advice

Bernalillo County New Mexico

1 Response

Swamp coolers are pretty effective cooling equipment for dry climates of the west and southwest. Arid climates have very low relative humidity levels out doors and that works for swamp coolers. when using an evaporator cooling technique, each time you drop the temperature 20 degrees you double the relative humidity.

If you start out with 95 degree F and a relative humidity of 25%, the swamp cooler can get you 75 degrees and 50% relative humidity. That humidity level is still pretty comfortable.

If you start out with 95 degrees and 40% rel. humidity. The swamp cooler is working harder to get the 75 degrees and you may be up to 80 - 85% relative humidity. You probably don't want to get the humidity much above 55%.

In Missouri we have high humidity levels and really cannot use a swamp cooler. One way to see what temperature you can get down to, is to check with the weather service to see what the dew point temperature is. The night time lows are pretty close to the dew point temps. The dew point temps are when the air is at 100% relative humidity. From a practical stand point, you don't want to cool lower than 20 degrees above the dew point temperature. That would be about 50% relative humidity.

Hope this helps.