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Indoor Air Quality & Humidity Control

Most people are concerned about high electric bills- understandably so. The settings for our thermostats is the logical place we go to aid in reducing the cost of electricity. Clearly, in most homes, the cooling and heating systems generate the most cost of wattage. Setting the “cooling” system “too high” can result in elevated humidity as humidity is removed from the home (in most homes) via the cooling system.

Moisture is removed from the air and travels through the condensation drain line to the

exterior of the home. This line needs to be cleaned periodically to avoid a “back up” of water into your home at the air handler. 6 month or 12 month service calls for HVAC should manage this maintenance aspect of the system(s). The system control is a “thermostat” usually located near the main return vent for the system. Thermostat alone is not adequate. A humidity gauge should be either built-in to

the thermostat OR you can purchase an inexpensive humidity gauge and place it near the thermostat. This should be checked regularly (several times a day as you walk past your thermostat) and 55% RH (relative humidity) should be maintained at the thermostat; this will allow for a maximum of 60% in farther reaching areas of the home. IAQ experts now place levels of 30-50% RH to be the “normal” range and now prefer 30-50. The climate you live in will dictate whether you need a “humidifier” or a "dehumidifier”. Most of my clients are located in Florida, Georgia - Southeastern States: DE-humidifier required! Ideally, whole house dehumidification is best. These systems can cost $2,000 attached to your central system. Alternately, an area dehumidifier can be purchased for at or less than $300. Depending on your space requirements, you may need more than one dehumidifier. Purchasing one with an internal pump will allow you to drain it to the outside or into a secure plumbing drain. Take all precautions to make a secure drain connection or you can create a water damage problem very easily if left unattended. The unit can be set at 55% and, usually, has a digital readout on the top of the unit that can be adjusted. If relying on the drain pan inside the unit (not a secure continual drain to the outside) make certain to purchase a device that has a large pan and be certain to empty it regularly (possibly a few times per day depending on conditions). Original publication dated January 2016 via Ericks Environmental

Setting the cooling system on a much lower-than-normal setting while operating

dehumidification equipment will augment the reduction of humidity in the space very

quickly. HVAC systems, when working properly, should produce 55% RH when set at 78 degrees For less during warm humid weather; MANY DO NOT. Systems should be checked by licensed and qualified HVAC person(s) to determine if the system is functioning properly. Common problems with HVAC systems that increase humidity include improper fan speed and standing water in air handler pan (horizontal systems with problematic directional drainage). Check YOUR system (when it is very warm and humid outside-70%>) and see what the highest temperature results in 55% RH; if this # is below 78 degrees F then have the system checked by a qualified person.

NORTH FLORIDA WINTER WEATHER WARNING: Since, at least 2010, our region of the

country has experienced more days with high humidity during our mild or cold

temperatures than low humidity. This usually begins in late October or November and

lasts through April with the most difficult months being December, January and

February. When the temperature outdoors is 60-75 degrees F, often, our cooling systems will not come on. If the humidity is high outside then humidity will build inside. If the humidity is allowed to be maintained for any length of time (and depending on the type of construction and any moisture problems known or unknown in, above or below the home) common mold spores normally found inside our home, will be allowed to proliferate; once this proliferation occurs you may begin smelling musty odors and you may begin seeing visible mold on leathers and such in closets, wood furniture and cabinets and other items. It are these common molds that are, normally, in low numbers, when allowed to grow to very high numbers that can cause some health problems and expensive mold remediation will be required.

Living Habits and Other Systems

Other activities can contribute to elevated indoor humidity. To name a few:



●Aquariums and fish tanks

●Humidifier (breathing equipment)

●Leaving doors or windows open during humid weather

●Leaks of any type

Current building codes require HVAC systems to have return ventilation in every room

(except kitchens, bathrooms, utility). This aids in better air flow through the home. Air

movement is critical. Ventilation in bathrooms is essential. Adequate CFM fan sizing and

proper operation of fans (including using the fans during and after showers) is very

important. If systems are not used or maintained, increased humidity can result. Placing

the bath fan switch tied to the light switch is a great way to insure use of the fan.

Proper ventilation at kitchen stoves will aid in removal of steam (and some volatile organic compounds- VOC’s). USING the devices we have is critical.

Other tools: Humidity data loggers can be purchased to tract humidity in your home or

rental property (this is a terrific tool for rental properties). You can also purchase a device that works with your smart phone to alert you when the humidity rises to an undesirable level. Moisture sensors are essential in all areas where plumbing or a/c is present. Maintain good humidity levels! Mold problem prevention is important. Before you leave for an extended period (2 days or more) create a plan for the humidity control of your home.

CENTRAL HVAC SETTINGS: NEVER SET YOUR FAN TO THE “ON” POSITION- ALWAYS “AUTO” unless your licensed HVAC professional instructs you to do so for a very specific reason (such as de-icing your coils). See our VOC Guide to help with other indoor contaminants and recommendations.

If you have questions please call. I am certain I haven’t answered all of your questions.

Cindy Ericks Call if you would like to discuss any of these concerns.


Ericks Environmental Consulting

Tallahassee Florida

IAQ-Environmental Consultant

State Certified Mold Assessor, MRSA721

State Certified Home Inspector HI2259

State Certified Radon Testing Technician R1549


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