Texas Mansion Has Big Geothermal System
The 33,000-square-foot custom home will cost upwards of $7 million when it’s finished this fall. Some of the amenities included in this three-story house are 30-foot-tall glass windows, an elevator, two maid quarters, indoor racquetball court, 20-seat home theater, and 3,000-bottle wine cellar with wine tasting room and cigar room attached. Of course, a master suite is not complete without its own kitchenette. And titanium-and-glass stairs greet visitors at the front entry.
Obviously, a really comprehensive HVAC system is needed for a house this size in order to keep its occupants comfortable. Designing and installing that system are Wayne E. Jones, CEO, and Robert L. Sparks, CFO, Geothermal Air Conditioning, Humble, TX.
SYSTEM GOES UNDERGROUNDAs can be surmised by its name, Geothermal Air Conditioning specializes in geothermal heat pump systems. Within that specialty, the company focuses on installing these systems in custom homes. This home in The Woodlands, however, is out of the ordinary compared to Geothermal Air Conditioning’s “normal” custom homes.
“Most of the custom homes we do are less than 10,000 square feet,” notes Jones. “This one’s in excess of 33,000 square feet — and that’s living area. There’s a total of 40,000 square feet under roof.”
Keeping that amount of space comfortable could be a problem in hot, humid Texas, so not surprisingly, the homeowners wanted to spare no expense on their mechanical systems. They contacted mechanical engineer Steve Redding to do the initial load calculations on the house, and also to suggest the optimal HVAC system. Redding had installed a geothermal heat pump system in his own house and enthusiastically recommended it to the homeowners.
The original load called for 40 tons of cooling, but so many changes were made (including the addition of the racquetball court), the amount soon zoomed up to 80 tons. The house at this point contains 13 WaterFurnace two-stage “Premier E” geothermal heat pump systems, along with another Premier E unit to handle dehumidification for the indoor spa.
No other special dehumidification equipment is needed for the rest of the house, because with the two-stage heat pumps, the fans run at a lower speed and also have higher capacity. Both factors make the systems well suited for getting rid of humidity. Because of potential mold issues, however, negotiations are currently taking place to also install energy recovery units, ultraviolet (UV) lights, and electronic air cleaners.
SPECIAL NEEDSThe wine room required a water-to-water unit to service a chilled-water fancoil that will keep the area at 55 degrees F. The attached cigar room has a dedicated exhaust system, so that odors do not travel throughout the rest of the house. A central exhaust fan system has also been installed for the entire house.
The house contains approximately 10 equipment rooms to accommodate the mechanical systems. The homeowners won’t have to worry about noise; spray-in insulation in the walls will absorb most of the sound.
The original design called for 20 to 30 water heaters placed throughout the house, but that has been changed. “They decided to bring in three 100-gallon water tanks, and we’ve got a 3-ton water-to-water unit built just to take care of those three units, with very quick recovery time,” says Jones.
The addition of the racquetball court late in construction meant another 5-ton Premier E unit was needed just for that area. In addition, special grilles were required that wouldn’t deflect the ball and also wouldn’t be damaged after getting hit many times.
One of the problems Jones ran into during construction was where to put the ductwork. With 11-foot ceilings and no attic, the ductwork — spiral sheet metal trunk lines with externally wrapped insulation — was designed as the project went along.
“In most houses, we’d be able to put the ductwork in the attic,” says Jones. “But this house doesn’t have one, so all the ductwork is behind fur downs. We had to be very selective about how to do it, and it was a lot harder and more time consuming than most jobs.”
Aesthetics count for a lot in a house of this magnitude, and perhaps understandably, the homeowners didn’t want to see any thermostats. “There are very small sensors throughout the house. The sensors send the temperature information to the 30 thermostats, which will be in the mechanical rooms, then the information goes to the zone controller, and to their home automation system,” says Jones.
TOTAL CONTROLThe house currently has 30 different zones, and the homeowners can go just about anywhere in the house and make changes on an easy-to-use touch pad. “If you’re downstairs in the theater room and you know you’re about to go to bed and you want to cool it down, just reach over to the keypad and take care of it,” notes Jones.
While the system in this house is extensive, there are a few things Jones would have liked to have done differently if he had been brought into the construction process earlier. For example, right now there are 13 different geothermal systems, and each 5-ton unit has five loops that go down in the ground. These are all connected together and come back to serve that one unit. Once that’s done several times, there are a lot of different loops in the ground, and there are 13 different circuits coming into the house.
“But if you connect them all together and they come into the house at one time and then branch out, then what you have is a better way of sharing the heat load, because you spread it out more evenly throughout,” says Jones. “It’s just a lot more efficient doing it that way.”
That aside, though, Jones is very excited about how the project is shaping up. “The homeowners are exceptional people, and we’re getting along just great.”
Publication date: 08/19/2002