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Basement Humidity Levels

Basement Humidity Levels

Drifthopper Member 2. NULL  Apr 12, 2007  100  2 Does anyone have any info on what is an “acceptable” level for humidity in a regular house basement? What I am asking on “acceptable” , is how high can the humidity be allowed to get before mold and mildew start to form? House is a two story colonial, built in 1977, poured concrete basement, about 800 sq. ft. , not finished, glass block windows with center screens that I do not open, washer / dryer / work bench / furnace and wood furnace off to one end under family room, sump pump in far corner…standard, solid basement. The guy that sold the house left an old dehumidifier, ( like from 1977 ). Seeing that it was old and having it look like a big energy monster, I would only run it every so often. Well, one yr, un-packing Christmas decorations, quite a few items had mold on them, these were tossed. So, two summers ago I got a new dehumidifier and a small digital temperature / humidity level reader : Temp on top , Humidity on the bottom. Last summer, I was running the dehumidifier on “dry” (there are three settings, normal, dry, and Extra dry” ) Dry is the middle setting. My typical humidity level was around 48% to 55% , basically right around 50%. BUT…..the machine was running ALL THE TIME.. So even with this new dehumidifier, it still added $15 to 20 bucks every month to the electric bill, spring , summer and early fall. This season, 2010 – To save on the electric bill, I have the dehumidifier set on “normal” , it does not run / cycle near as much, but my humidity level is around 60 % to 67% ( 67% is the highest I’ve seen on the digital reader) Basement temperature is about the same, 62, 64, sometimes 68, depending on how hot it is outside. Now ….i understand that all houses are different and everyone’s situation/set up is different, but there has to be some type of baseline to say what is ok, and what is not. Any input (or links for info) is greatly appreciated. Cuttin' wood and Keepin Warm in Western New York. share share on twitter share on facebook email link
basement humidity levels 1

Basement Humidity Levels

Does anyone have any info on what is an “acceptable” level for humidity in a regular house basement? What I am asking on “acceptable” , is how high can the humidity be allowed to get before mold and mildew start to form? House is a two story colonial, built in 1977, poured concrete basement, about 800 sq. ft. , not finished, glass block windows with center screens that I do not open, washer / dryer / work bench / furnace and wood furnace off to one end under family room, sump pump in far corner…standard, solid basement. The guy that sold the house left an old dehumidifier, ( like from 1977 ). Seeing that it was old and having it look like a big energy monster, I would only run it every so often. Well, one yr, un-packing Christmas decorations, quite a few items had mold on them, these were tossed. So, two summers ago I got a new dehumidifier and a small digital temperature / humidity level reader : Temp on top , Humidity on the bottom. Last summer, I was running the dehumidifier on “dry” (there are three settings, normal, dry, and Extra dry” ) Dry is the middle setting. My typical humidity level was around 48% to 55% , basically right around 50%. BUT…..the machine was running ALL THE TIME.. So even with this new dehumidifier, it still added $15 to 20 bucks every month to the electric bill, spring , summer and early fall. This season, 2010 – To save on the electric bill, I have the dehumidifier set on “normal” , it does not run / cycle near as much, but my humidity level is around 60 % to 67% ( 67% is the highest I’ve seen on the digital reader) Basement temperature is about the same, 62, 64, sometimes 68, depending on how hot it is outside. Now ….i understand that all houses are different and everyone’s situation/set up is different, but there has to be some type of baseline to say what is ok, and what is not. Any input (or links for info) is greatly appreciated. Cuttin' wood and Keepin Warm in Western New York. share share on twitter share on facebook email link
basement humidity levels 2

Basement Humidity Levels

Does anyone have any info on what is an “acceptable” level for humidity in a regular house basement? What I am asking on “acceptable” , is how high can the humidity be allowed to get before mold and mildew start to form? House is a two story colonial, built in 1977, poured concrete basement, about 800 sq. ft. , not finished, glass block windows with center screens that I do not open, washer / dryer / work bench / furnace and wood furnace off to one end under family room, sump pump in far corner…standard, solid basement. The guy that sold the house left an old dehumidifier, ( like from 1977 ). Seeing that it was old and having it look like a big energy monster, I would only run it every so often. Well, one yr, un-packing Christmas decorations, quite a few items had mold on them, these were tossed. So, two summers ago I got a new dehumidifier and a small digital temperature / humidity level reader : Temp on top , Humidity on the bottom. Last summer, I was running the dehumidifier on “dry” (there are three settings, normal, dry, and Extra dry” ) Dry is the middle setting. My typical humidity level was around 48% to 55% , basically right around 50%. BUT…..the machine was running ALL THE TIME.. So even with this new dehumidifier, it still added $15 to 20 bucks every month to the electric bill, spring , summer and early fall. This season, 2010 – To save on the electric bill, I have the dehumidifier set on “normal” , it does not run / cycle near as much, but my humidity level is around 60 % to 67% ( 67% is the highest I’ve seen on the digital reader) Basement temperature is about the same, 62, 64, sometimes 68, depending on how hot it is outside. Now ….i understand that all houses are different and everyone’s situation/set up is different, but there has to be some type of baseline to say what is ok, and what is not. Any input (or links for info) is greatly appreciated.
basement humidity levels 3

Basement Humidity Levels

Sucking the air out of the basement will not maintain the proper humidity levels in the basement. When you pull air out of a basement, it pulls make-up air in either through the exterior or from the upper levels of the house. On a hot and humid day, the air from the house and the outside air will have a high moisture content thus introducing more moisture into the basement through the make-up air.
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Basement Humidity Levels

Simply put, when air cools, its relative humidity levels increases. The best way to maintain a 50% relative humidity level in your basement is to keep it warm in the heating season.  Most people are prone to turning down the heat in the basement if they are not using it. However, when the air is warming and cooling the air will actually create more moisture that may lead to mold and mildew growth.  May suggests keeping the basement consistently warm at least at 58 to 60 degrees F in the heating season.
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Basement Humidity Levels

What should my humidity level be, and how do I know if I need a dehumidifier? Relative humidity levels above 60% can cause mold or mildew to grow, resulting in musty smelling air and unhealthy airborne mold spores. The ideal relative humidity level should be somewhere between 30% – 50%. Many basements in warm humid climates need dehumidification during the summer months to keep mold growth at bay. If you notice a musty smell or odor in a room, it will probably benefit from a dehumidifier, as drier air is not only healthier for you but will also be less likely to smell or have a stale, musty odor. A quick and inexpensive way to check the relative humidity level in any room is with a hygrometer.
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Basement Humidity Levels

Dehumidification can be used as a means of reducing the symptoms of humidity and odor in a basement, but it is not a permanent or complete solution. In fact, if a dehumidifier is used in a basement with moisture problems, it may cause greater damage. By drying out the basement air, moisture is drawn into the basement more rapidly causing efflorescence and spalling of concrete and further damage to interior finishes.
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Basement Humidity Levels

Looking at the comments to the question, I believe even running the dehumidifier at a higher setting will have it running lots. The amount of moisture traveling to your basement from the open upstairs windows will be substantial, and you will be effectively “dehumidifying the outdoors”. I would suggest looking into methods of limiting airflow between your upstairs and your basement. That being said, I would suggest keeping your humidity below 60%, as you may see mold growth above that RH.
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Highbeam Minister of Fire 2. NULL  Dec 28, 2006  12,882  2,315 Loc: Mt. Rainier Foothills, WA I was told to keep my bedroom's air below 50% to limit the dust mites. In reality we are nearer 60% on average. For a basement, your current 60-67% is just fine and not going to cause mold on the surface if you are getting 60-67% everywhere. My guess is that if you could measure the humidity between an exterior wall and a stack of boxes (where you found mold) you would find much higher RH levels than you do out in the middle of the room or near the dehumidifier. You need air circulation to get all the water out. Blaze King Princess Ultra house stove Englander NC30 shop stove share share on twitter share on facebook email link

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