TES: A Field Study in the Science of Drying
April 11, 2006
TES, or Thermal Energy System, is the result of a collaborative effort by Jeremy and Bridgepoint Systems. Basically, TES uses a propane gas burner to superheat coils through which an industrial pump circulates a water/glycol mixture, much like a hydronic heating system in the floor of a home, but at much higher circulation volume. The hot water passes through hoses to a heat exchanger. The heat exchanger has a radiator with fins that allows transfer of heat energy to air that is propelled through the Heat Exchange Assembly Transfer (HEAT) unit by inserting a standard centrifugal airmover on top. This lowers equipment cost by utilizing equipment that the restorer already has.
Once the heat energy is transferred to the air, it is propelled out of the HEAT unit's snout and directed where it is needed - under carpet and over pad; under containment installed over a strip wood floor; or over containment hung from floor joists to contain hot air against the bottom of plywood or OSB subflooring. A single TES unit can operate up to four HEAT units.
I know what you're thinking: That's all fine and good, but in the end, only one thing really matters: how does it perform?
I was invited to participate in a test of the TES concept at the IICRC-approved ASD training structure at the National Center for Advanced Training in Anniston, Ala. Joe Dobbins operates NCAT, which has a 1,250-square-foot flood house equipped with almost every construction configuration that typifies today's residential construction practice.
The test objective was to demonstrate the use of the temperature drying principle in speed-drying difficult-to-dry (Class 4) materials under realistic water damage constraints. Specifically, the objective was to test the Bridgepoint TES concept to demonstrate how raising the temperature of structural materials increases water evaporation from surfaces or from within materials, and the relationship of temperature to the other principles of restorative drying (water removal, evaporation, dehumidification) as outlined in IICRC S500.
Testing was conducted at the National Center for Advanced Training's IICRC-approved ASD facility and involved:
- 24-ounce tufted nylon level-loop carpet direct glued to concrete slab.
- 32-ounce tufted nylon Saxony carpet stretched over six-pound bonded polyurethane cushion on concrete slab.
- 28-ounce tufted olefin Berber stretched over six-pound bonded polyurethane cushion over two sheets of 1/2-inch plywood.
- 3/4-inch solid oak strip wood flooring planks nailed tongue-and-groove over 3/4-inch plywood, and the facility's pier-and-beam crawlspace with concrete slab flooring.
Extraction was accomplished using a U.S. Products Flood Pumper, which incorporates two two-stage centrifugal-bypass vacuums and automatic pump-out. Extraction tools included a HydroX self-propelled unit with two 50-pound weights added, and technicians weighing 160 to 180 pounds for a total extraction head weight of 345 to 365 pounds. A medium-sized Water Claw with a 160-pound technician was used for extracting in confined areas. A light wand was used on the low, level-loop carpet direct-glued to the concrete slab in the playroom. A vacuum squeegee was used on the solid oak flooring in the kitchen.
Following extraction, centrifugal (squirrel-cage) airmovers were installed at the rate of approximately one per 16 linear feet of wall space. A HEAT unit incorporating a single centrifugal airmover was installed in each room of wet carpet over pad, or wood flooring inside the facility. Each HEAT unit was installed under the carpet in order to confine heated airflow within the area of the most difficult-to-dry materials, i.e. carpet cushion, pad and the concrete subfloor.
By raising the temperature of the slab, water that had condensed and was held on its surface evaporated far more rapidly. Even with circuit breaker problems, carpet and pad installed over slab in the playroom was dry within 18 hours.
A structural cavity drying system (SCDS) inter-air drying system using six clear plastic mats with 1.5-inch hose connectors and negative pressure was installed on the solid oak flooring in the kitchen. Mats were taped in place using painter's tape. The U.S. Products Flood Pumper was attached to the negative pressure drying mats to remove excess moisture from between the floor planks. This system ran for 45 minutes and considerable additional water was removed, based on visual observations. After extraction, the SCDS unit was connected to the same mat system and turned on.
One HEAT unit was installed in the kitchen/dinette area over the solid oak flooring. The entire wood flooring in the kitchen/dinette area, along with the SCDS in a negative pressure drying mode, was covered (contained) with six-mil polyethylene plastic. This contained the hot air being generated by the HEAT unit. One thermostat-controlled centrifugal airmover, with 15-inch lay-flat ducting, was installed in the kitchen of the house to ventilate excessive heat from ambient airspace within the structure and maintain ambient temperature at approximately 87 degrees. The exhaust system is designed to maintain ambient temperatures at tolerable levels, especially when coupled with air conditioning, and to focus temperature where it is needed most.
The kitchen and living room subflooring were isolated from the rest of the crawlspace using six-mil polyethylene plastic that was stapled to floor joists and support beams. One HEAT unit was installed at the entry to the crawlspace, along with one Phoenix Focus axial airmover producing approximately 3,000 cfm, to ensure hot air distribution and circulation throughout the contained area.
Monitoring was accomplished using a Visalia thermo/hygrometer; a Dri-Eaz Hydrosensor; a Tramex moisture meter, and a Moisture Pro penetrating moisture meter using hammer probe.
The entire system was set up and operational by 1:30 p.m. on the first day of drying. The temperature being produced by the HEAT unit over the wood floor and under the polyethylene plastic containment reached 136 degrees and 8.8 percent RH for a specific humidity of 69 GPP and a dew point temperature of 57 degrees.
- Temperature of the carpet in the center of the room was approximately 112 degrees.
- Temperature of the base molding reached approximately 104 to 114 degrees.
- Temperature of the gypsum board (drywall) reached approximately 97 to 101 degrees.
- The temperature of the kitchen hardwood floor was 121 degrees.
At 9 a.m. on Aug. 3, 2005, we discovered that a tripped circuit had turned off two 4.7-amp airmovers, the Dry Force floor-drying unit and the TES circulation unit at approximately 11:00 p.m. the night before, according to a data logger positioned in the kitchen. Circuit breakers were reset and the system was restarted at 10 a.m. on Aug. 3. Considering downtime, plus the time it takes to bring structural materials back up to temperature, we lost some 15 hours of effective drying.
Thorough extraction of carpet and pad is essential to reduce drying time, contrary to the recommendations of some hot air system manufacturers. Due to the amperage required to operate the Dri-Eaz Turbodryers (4.7 amps), overloading of 15-amp residential circuits was a problem. This resulted in the loss at least 17 hours of drying time, when we consider the time to bring materials to appropriate temperature.
Containment - either poly plastic or floated carpet - is necessary to confine heat and transfer it to difficult-to-dry surfaces or materials. Initially, the crawlspace was not confined and temperature build-up in this area was marginal at best. It was necessary to hang poly plastic sheeting from floor joists to contain heat effectively, thereby exciting absorbed water molecules in the plywood subfloor for faster evaporation, in this critical drying area.
Floated carpet was dry in 3 to 4 hours. Carpet cushion was dry within approximately 6 to 8 hours. In addition, heat radiated from under the carpet to the base molding and lower wall area generated a temperature range of 97 degrees to 101 degrees at those surfaces, which resulted in rapid drying there as well.
So What's the Bottom Line?After wetting the structure times over 24 hours, we measured surface, core and subsurface MC readings in the finished wood floor in five test areas using a moisture meter with hammer probe. The ending MC percentage is adjusted for material temperature. The mean averages for the finished floor and adjusted averages for the subfloor both before and after drying are summarized in the following table.
So what's the bottom line?
Using direct application of hot air drying technology, we were able to dry carpet in three hours and pad in less than eight hours. Moreover, hardwood floor and subfloor drying has been reduced from a week or more to around 30 hours.
The goal for IICRC-certified drying professionals is to dry an entire structure subject to Category 1 water and Class 2 or 3 water losses to 24 hours total. Thanks to industry manufacturers, and in no small part to Jeremy Reets, we anticipate that, with the development of TES technology, this goal is within reach.