Humidity and Mold Problems in Multi-Story Condominiums
Contributed by Scott Tracy, owner
In my many travels and inspections around Central Florida, I have come across a unique problem associated with multi-story condominium buildings. This problem seems to be somewhat pervasive in the Winter Garden area.
Unfortunately I have found that there is a lot of myth’s or disinformation out there as to why this problem is occurring. In many cases Tenants/Condo Owners are being blamed for causing mold growth in their units by either being negligent or not using their HVAC systems properly. As a result there are many Tenants/Owners being driven to distraction with guilt and stress as well as suffering property damage that they cannot control.
As I mentioned above, I have inspected many of these cases (some in the same complex), and since I cannot review each and every one of them, I found one inspection that encapsulates all of the units that I inspected. The reader needs to know that there is some common denominators to be found in these situations:
1. Sometimes dehumidifiers are found installed in the same closet as the AC Air Handler.
2. Sometimes a Humidistat Controller will also be installed on the wall near to the AC Air Handler Closet.
3. Normally there will be a “fresh-air” supply duct coming out of the wall in the AC Air Handler Closet.
Pictures showing AC Air Handler Closet with permanently installed dehumidifier.
This is a copy of an email I sent to a client that I worked for last year. In this case I was hired by a Tenant who was experiencing mold problems in his unit.The reader will find the information about “Aircycler” below pretty interesting. While many of these affected units do not have this type of controller installed in their units, the notes that I highlighted in red infer that these fresh air ports can be a big problem in humid climates.
I have deleted the names for obvious reasons.
I have found that a lot of these complexes, many built by the same builder, have similar issues. It is also obvious to me that in the past there were actions taken by both the Condominium Associations and the Condominium Owners to address this problem. The evidence is after-construction, retro-fitted dehumidifiers that are now installed in a lot of the Condominiums.
Here is the email:
From: Scott Tracy [mailto:stracy@SERVPROaw-wo.com]
Subject: Mold problem in Condominium
Per your request, I returned to your unit today to further investigate the source of the high humidity problem. This high humidity caused the mold contamination to both the walls of the Condominium and to your contents in the unit.
1. Obviously this Condominium has a fresh air supply duct opening located in the Air Handler closet to the left of the air handler (see below). This allows unconditioned fresh air to be mixed into the Condominiums interior air periodically to help dilute indoor air pollution. Since we are in Florida, during certain times of the year, this unconditioned air can be severely elevated with high humidity.
2. This unconditioned air is drawn from the fresh air supply into the Condominium in 2 ways:
One way is part of the original design. When the Air Handler is running, the air returning to the Air Handler causes a low pressure environment in front of the fresh air supply duct opening which pulls air from the exterior to the interior (see pictures below).
The second is not part of the intended design. When bathroom exhaust fans are engaged or the Clothes Dryer is working, these appliances pushes air out of the Condominium. Replacement air then needs to be sought. This replacement air would also come from this fresh air supply duct opening.
3. To counter elevated humidity in the Condominiums air, both the Air Handler and the installed dehumidifier work together, and are designed to condense and remove this excess moisture.
4. If either one or both of these fail, elevated humidity will permeate the unit and cause mold. Both point 5 & 6 below show a failure with both units.
5. I inspected the installed dehumidifier. The unit is not working properly. The unit is running, but my hygrometer shows that the exiting air shows no drop in relative humidity. The drain bucket was also inspected, and it revealed no evidence of any water or moisture. This indicates the dehumidifier is basically using electricity, but not doing its job
6. You also mentioned to me that there was a problem with the Air Handler in the past. You indicated there was an extended period of time where the Air Handler never shut off. In spite of your efforts to use your thermostat to shut the unit off, this was not successful. You called the units owner and an HVAC Contractor came to the Condominium to correct the problem. I will tell you that there were two consequences that occurred when this happened. Both of these consequences resulted in additional elevated humidity in the home.
a. If the Air Handler blower never turned off, any water condensate that might have accumulated in the AC pan below the cooling coils (that normally would drain down the pvc drain line), would have just been evaporated back into the Air Handler air flow, and therefore back into the Condominium.
b. Additionally, if the Air Handler blower never turned off, this in turn continually pulled additional humid air from the above mentioned fresh air supply duct opening. This compounded the problem and caused uncontrolled humidity in the Condominium, which in turn allowed for mold growth.
7. Furthermore, the AirCycler Programmable Ventilation Controller was found to be disconnected in the Air Handler closet. This is part of the fresh air supply’s design. Since this may have been disconnected by the visiting HVAC Contractor, the presumption is that this controller may have been interfering with the HVAC thermostat, which in turn may have been the reason why you could not get your Air Handler to shut off in the past.
8. Please see the information I have cut and pasted into this email below. This comes from the Controller Manufacturer that is installed in the Condominiums Air Handler closet. Please note the text I highlighted in red. This page mentions the danger of continuously running the “central system fan” (or Air Handler blower I mention above), no less than 4 times.
9. The only good news about this is that now that the source of the problem has been identified (equipment failure), the owner of this Condominium has the ability to mold remediate his unit and there may be coverage under Homeowners Insurance. It would normally be considered a “covered” loss. Unfortunately, the Condominium Owner’s Insurance will not extend any coverage for your contents as they are not part of their coverage.
The AirCycler is a programmable ventilation controller for Central Fan Supply Ventilation designs. When you are providing fresh air for a house through a fresh air supply duct connected from the outside to the return plenum of the HVAC system it is essential to have the air handler operate on a scheduled cycle to provide fresh air for the house. This programmable timer is connected to the thermostat connection of the air handlerto monitor the run time of the air handler and when needed turn on the air handler to meet the fresh air requirements of the house. The timer will take advantage of free distribution of ventilation air during thermostat driven heating or cooling operation and provides periodic whole house mixing and ventilation air distribution during periods when thermostat driven heating or cooling operation does not meet the programmed fresh air demand.
Air Cycler FR
Outside Air Duct Into The Central System Air Handler Return Plenum
Ventilation systems that provide ventilation air through a duct that extends from outdoors to the return plenum of a central air handler only supply ventilation air when the fan is operating. Rather than operating the central system fan continuously, which can waste energy and can also lead to moisture related problems in humid climates, the recycling control can be set to periodically distribute ventilation air during stagnant periods when there is no call to circulate air for purposes of heating or cooling.
An economical and effective ventilation system, using the AirCycler, would be a 6" to an 8" diameter insulated duct (depending on the house size) from outdoors to the return of the central air distribution fan (see diagram below). This outside air should be filtered before it enters the central return duct, and a balancing damper is advisable to give additional field control of the delivered outside air volume. The AirCycler control would be installed at the central fan cabinet, connecting to the thermostat wiring terminals. It functions to guarantee that fresh air will be periodically distributed throughout the house when there is no call for heating or cooling, but it is energy efficient since it only does this if the central fan has not operated for a preset time. A very important added benefit, is that builder call-backs due to thermal comfort or air quality problems may be greatly reduced because the AirCycler will even-out temperature, humidity and stuffiness conditions between rooms and the main body.
For single-point exhaust or single-point supply ventilation systems, the supply or exhaust point is usually located in the main body of the house. In this case, closed rooms, such as bedrooms, will not receive adequate ventilation air unless the central system fan operates to mix air between the main body and the closed rooms. Rather than operating the central system fan continuously, which can waste energy and can also lead to moisture related problems in humid climates, the AirCycler control can be set to periodically distribute ventilation air throughout the house during stagnant periods when there is no call to circulate air for purposes of heating or cooling.
Enhanced Humidity Control Systems
In humid climates, dehumidification, separate from the central cooling system, may be usedto maintain comfort in seasons where there may be long periods of high humidity while indoor temperatures are within personal comfort ranges. In order to reduce system cost, it may be practical to locate a single dehumidifier in the main body of the house. In this case, closed rooms, such as bedrooms, will not receive the dehumidification benefit unless the central system fan operates to mix air between the main body and the closed rooms. Rather than operating the central system fan continuously, which can waste energy and can also lead to moisture related problems in humid climates, the AirCycler control can be set to periodically distribute dehumidified air throughout the house during stagnant periods when there is no call to circulate air for purposes of heating or cooling. For either dehumidifiers that are connected to the central air distribution system ducts, or for dehumidifiers that are stand-alone, humidistats are usually located in a central area and are expected to serve an entire zone that usually includes closed rooms, and often, more than one floor level. Humidity conditions can vary widely between the humidistat location and extremities of the space the humidistat serves. A practical solution to this problem could be to utilize the central system fan to average the overall space conditions by mixing. Rather than operating the central system fan continuously, which can waste energy and can also lead to moisture related problems in humid climates, the AirCycler control can be set to periodically mix house air during stagnant periods when there is no call to circulate air for purposes of heating or cooling.
I hope this helps somewhat.
Needless to say, the above diagnosis helped this particular customer avoid being blamed for causing the high humidity and mold in the condominium. Even though the condominium owner used this information to find a fix to his problem, the Tenant (my customer) was able to move out without and penalty.
For those readers that live in similar multi-story complexes (be they apartments or condominiums), if any of the above information sounds similar to what you are experiencing, please contact a professional to come out and help you figure out why this is happening.