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Ideal basement humidity level


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  • Ideal basement humidity level

    I really don't know if this is the right forum to ask this but here it is. Does anyone know what is the ideal humidity level in the basement to avoid molds and mildew? I just recently bought a dehumidifier in the basement and my humidity level, based on the Radio Shack hygrometer, is at 42%. Is this good? Thanks.

  • #2
    The humidity constantly changes with the weather.

    It is nearly impossible to reduce the humidity below the outdoor air level, however the closer you can maintain the humidity to the air level the better.


    • #3
      Most home-owners feel very comfortable with a Temperature of 68-72 F, and a Humidity level of 25-45 %. Hube


      • #4
        My books say 68 to 72 F, 20 to 22 C with 40% to 65% humidity.


        My mistakes dont define me they inform me.
        My mistakes dont define me they inform me.


        • #5
          IDEAL humidity in anyones book is..... 35-40 %


          • #6
            Check out the website at These people desire more in the 45-55% humidity range, and the chart shown on that page indicates that 45-55% is also ideal for many people.


            • #7
              hunidity help

              my basement bedroom is reading 70F and 90% humidity
              out door temperature is about 68F and 94% humidity.
              window was open as well as door to rest of basement.

              basement rec room was registering at 72F and 80% humidity.

              hearing all the talk about dust mites and spores is really making me uncomfortable.

              We are having concerns with cooling the house and keeping humidity levels down.

              please help
              ideally i would like to have 70F or lower and 45% or lower humidity.. is this possible
              is it more a matter of keeping the humidity with in a percentage of out door humidity or with in the house itself.


              • #8
                No wonder your basement humidity is so high, you have the window and doors open. You mention your concerned about keeping the house around the 70 F, does this home have a HVAC unit ? With the AC on you will reduce your room humidity by the simple process that the AC uses to cool the air, it pulls moisture out of the air that's why you see the little drip line near your cooling unit.
                A simple and cheap dehumidifier available at all big box stores will also help reduce your humidity levels. Most have sensors that you can preset the desired humidity levels, they collect the moisture from the air and collect it in either a tank for your disposal or they can be plumbed very easily directly into a floor drain etc...
                Little about a lot and a lot about a little.
                Every day is a learning day.


                • #9
                  Definitely close the windows and doors to the outdoors.

                  Many people will install a dehumidifer(s) in the basement. There are portable units that cover a relatively small area and you have the water discharge issue which can be piped to a floor drain or to a tank. Large dehumidier units are made that run in the $1000 area which might help for the entire space. It depends on your situation.

                  Assumptions: No HVAC for basement space and running duct lines will be relatively simple above the ceiling (if there is a ceiling).

                  My suggestion is to look at the small supplemental HVAC units depending on the square footage involved that are made for porches, sunrooms, new additions etc. and have one installed. It will function just like a regular central HVAC unit. You will probably have to run some duct work to the various rooms in the basement. Run fans too to keep the air moving.

                  Or you could enlarge your present HVAC system to include the basement space.

                  Another option is if the space is not heated or air conditioned is to essentially install vent fans in the foundation wall and keep those running to discharge the cooler humid air. Having the intake at the base of a wall where the coldest air is normally present can be done with flexible pvc pipe secured to the vent fan.

                  Shoot for 50-60% humidity.

                  Hope this helps.
                  Last edited by LittleChief; 07-02-2009, 01:45 PM.


                  • #10
                    When you search on the internet for "Logidry" you'll find a system which evaluates the humidity inside and outside and switches on or off a fan, a ventilation valve, automatic window opener, heater, or other components.
                    So an optimal ventilation and drying of the basement is guaranteed.