FSEC Looking for Vacant Homes to Study Ways to Control Relative Humidity and Avoid Mold in Seasonal-Resident Homes

The Florida Solar Energy Center (FSEC) is looking for “a few good houses” for their research on relative humidity control in vacant homes. If you’ve got a house located within 60 miles of Cocoa, Florida, and you’d like to make it available for this monitoring project that will help improve the cooling and comfort levels in Florida homes, let us know about it.

The study will be conducted between now and October, and is a Phase II project of ongoing investigations of issues and approaches to relative humidity (RH) control in homes. Financial incentives are available for homes chosen for the study.

Each year, more than 900,000 Floridians leave the state for part or all of the summer. These residents must decide how to best control RH in their homes that will be left unoccupied during hot and humid summer months. FSEC staff conducted research last year under funding from Florida Power and Light to determine guidelines for vacant homes to avoid mold problems while minimizing both customer energy usage and electrical load during utility peak hours.

Two objectives were set for determining whether adequate humidity control was being achieved. RH should stay below 65% most of the time and below 70% nearly all of the time. Seventy percent RH is considered to be a critical level, above which mold growth is likely or probable.

Two methods were identified that did not provide good control of indoor RH.

1. Letting the house “float” (no air conditioning or other systems operating). In most homes, “letting the building float” resulted in average RH of about 70%, which is marginal at best.
2. Setting the air conditioner at 850F and letting the system cycle ON and OFF to maintain that temperature. Setting the thermostat at 850F did not yield acceptable RH control primarily because the air-conditioning system did not operate sufficient time to yield adequate moisture removal.

Three methods were identified that could provide good control of indoor RH.

1. Running the AC system at a low temperature (such as 740F) for a two-hour period such as 3 to 5 a.m. In most homes, this approach keeps RH below 65% most of the time.
2. Operating a dehumidifier can effectively control indoor RH. In many homes, operation of the dehumidifier on a timer for 3-4 hours per day keeps RH below 65% RH. In cases where the home has higher air leakage (infiltration), or in larger homes, longer run times may be necessary. Dehumidifiers generate a good deal of heat. The heat generated by the dehumidifier lowers the RH because each degree Fahrenheit of temperature rise lowers RH by about 2 percentage points.
3. Space heating in the summer can control indoor RH because higher temperatures produce lower RH. Therefore, if a house is heated to 88-900F, then the RH will be about 65% most of the time just because of the higher temperature. Initial indications show that this approach consumes more energy than the other two approaches, especially if space heating is done with electric resistance heat.

The first two of these three methods are considered, at this point, to be the most proven. Now the researchers are looking for some vacant houses in which to set up their monitoring equipment to further study these concepts. If you have a home near Cocoa that you’d like to make available to the researchers, call Chuck Withers at (321) 638-1419, Jim Cummings at (321) 638-1403, or Danny Parker at (321) 638-1405.

The Florida Solar Energy Center, a research institute of the University of Central Florida, is the largest and most active state-supported energy research center in the country. Current research activities include solar water and pool heating, solar electric and distributed generation systems, energy-efficient buildings, alternative transportation systems, hydrogen fuel, fuel cells and other energy areas. For more information about the center, visit www.fsec.ucf.edu or call theFSEC Public Information Office at (321) 638-1015.

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