Ventilation is easy, even in a hot, humid climate. . . or is it?
Ventilation in a hot, humid climate can create serious issues for everybody from occupants to builders to lenders, virtually everybody
However, installing ventilation systems can create triple business profits for those who realize that creating mold issues creates new profit opportunities for new dehumidifiers, new air conditioners, and mold remediation
Ventilation Best Practices (And Cautions)
- Always provide fresh air, but do not over-ventilate!
- Ventilate only when a home is occupied. Use automatic or “Smart” controls.
- Automatically adjust ventilation rate according to how many occupants are present and automatically adjust the ventilation rate accordingly.
- Install a humidity controller which will sense indoor relative levels and will interrupt ventilation if the existing air conditioner cannot handle the moisture load. TIP: Dehumidistats are not up to the task.
- Provide a low maintenance and easy access filter at the point where air enters the home
- Choose a filter with a MERV rating of at least 12 and which does not require service more often than every 18-24 months
- Table lamp timers are a poor choice for operating ventilation systems. Adjustment is generally guesswork. When high humidity occurs, table lamp timers do not take any corrective action and humidity issues may become far worse as an air conditiopner’s delta t performance further declines.
- If a table lamp timer setting is set perfectly, and the air conditioner’s ability to dehumidify declines, expect mold and mold odor issues to get worse and worse.
- Ventilation systems that are powered by the air handler have the exact same issues, except that they use a high energy consumption fan 1/3 to 3/4 horsepower to achieve the same result that can be achieved with a 15-watt fan. And they cannot use smart controls to avoid moisture issues.
- Passive ventilation systems that incorporate a duct terminating in an air handler closet or a return duct are out of control and cannot respond to smart controls. There are entire apartment complexes that incorporated passive ventilation systems (actually radon mitigation system in many cases) with no controls with serious mold issues with the cause going unrecognized.
- In one large complex on Davis Boulevard in Naples, it is estimated that the property’s FMV has declined by millions of dollars as a result of continuing mold and moldy odor issues. Almost every single unit has experienced recurring mold issues that require periodic, repeat, mold remediation because no one has recognized that the passive ventilation system was the cause. The corporate decision-makers believed the radon mitigator who told them that the air conditioner would take care of humidity.
- A dehumidifier may not be needed if over-ventilation is prevented. Smart ventilation controls will monitor indoor conditions and adjust ventilation rates to keep moisture loads within an existing air conditioner’s dehumidification capability.
- Although thousands of ERVs, Energy Recovery Ventilators have been installed in hot, humid climates, experience reveals that most of them are turned off soon after installation because when indoor relative humidity is high. When moisture reduction is most needed, ERVs actually humidify the incoming air instead of removing moisture. If indoor relative humidity is an issue, look for an ERV and turn it off and block the ducts. That alone may solve the humidity problem.
- Very often, a simple, low-cost smart ventilation system can successfully replace a ventilating dehumidifier for reason that ventilating dehumidifiers almost always grossly over-ventilate. This writer recently viewed a high-end condo in Naples with a minor radon issue. The radon mitigator chose to install a ventilating dehumidifier that delivered over 300 cfm of outdoor air at a cost of close to $20,000.00 including all newly-required ductwork and drywall work. This writer estimated that 20 cfm would have been sufficient to solve the minor radon issue and would not have required a dehumidifier, as the condo had a high-performance HVAC system. Dehumidifiers, like air conditioners, do not even begin to dehumidify until they have operated for about 10-20 minutes. For the first 10-20 minutes, this system delivered over 300 cfm of un-dehumidified, hot, humid outdoor air into the condo for before it even began to dehumidify the ventilation air. Occupants would have noticed a very big jump in humidity for that beginning during that period, a likelly for an hour or so afterwards.. The ventilation dehumidifier added fresh air on a timer. It did not have smart controls. It is hard to conclude that the radon mitigator was more interested in the success of the installation.instead of a stunning profit.