Indoor Relative Humidity Reminders

Controlling and monitoring humidity and moisture indoors is healthy

by Wayne Deane

Editor's note: Since so many of you seem to have "mold on your minds" and what is the "right" humidity level I thought you would be interested in what Wayne Dean one of our experts has to say on the matter.

INFO LINKS Dehumidifiers Overview - view all Dehumidifiers sold by AllergyBuyersClub.com Dehumidifiers Comparison Chart - a comparison with pluses and minuses of all the best Dehumidifiers Mold Solution Guide - a quick buyers guide of the best recommended products to solve mold allergy problems Best Dehumidifier Articles - Editor's top picks on dehumidifier info

I have an interest in solutions to illnesses which may have a common origin in the simple condition of high indoor relative humidity. It seems that many informed folks are of the opinion that relative humidity above 50% provides a friendly environment to molds, bacteria, and dust mites, all of which negatively influence health.

My personal crusade is to encourage folks to monitor and to control the relative humidity in their environments so as to determine if they find a connection.

In Florida's hot, humid climate, I find that such an interest is very appropriate, however rare. It is my belief, based upon my testing, that relative humidity levels are not well estimated, and that exposures are often much higher than expected. Some time back, we had occasion to do radon work in an adult congregate living facility in SE Florida. The three story building felt clammy and cold. Our instruments told us that the indoor relative humidity was 92% and the temperature was 72 degrees most of the time. The property managers were unconcerned with our findings, feeling comfort in the notion that they had a maintenance contract with an A/C firm to take care of matters, and that they were sure everything was A-OK. I believe that the building received frequent repainting. There is a critical interaction between A/C and high humidity (called micro-climates by experts that I have met) that I suspect creates a more dangerous condition in some cases than would exist were there no A/C in operation. Within the Florida radon mitigation industry, addition of outside, unconditioned air leads to significant indoor relative humidity increases. The limitation of the Florida Radon Code of a maximum of 15 CFM per person is regularly and grossly exceeded. We have overheard "Radon Experts" advise property owners that 70% indoor relative humidity is normal in an air conditioned environment in Florida. We believe that 49-51% is normal and desirable in this hot, humid climate. And we think it is much safer for folks and fauna as well as building materials and property. And we think that to say that all you need to do to get rid of mold is to "spray it with bleach" is irresponsibly negligent and risky to a substantial fraction of the population which may be sensitive to humidity-loving malevolent organisms.

For more information on Wayne, read his excellent FAQ on radon remediation

First Published: late August 2000
Updated: April 2007

Send this article to a friend

.................................................. .................................................. .................................................. ..................................................