PARKER, Colo. - When Tim McTavish set out to remodel his home, his plans included increased square footage for the living space, radiant floor heating throughout the entire structure, snow melting for exterior surfaces, and an in-ground swimming pool.
McTavish, a self-proclaimed techno-junkie and aficionado of sustainable, energy-efficient building concepts, was looking for exceptional means by which to heat and cool his newly updated residence. “It all started because I wanted an energy-efficient way to keep the pool warm,” he recalled. “I explored all the different options available, and I settled on solar.”
However, solar was just the beginning. After meeting with Al Wallace, president of Energy Environmental Corp. (EEC, a company specializing in design, installation, and consultation for integrated renewable energy systems), the home was completely overhauled with an elaborate, energy-efficient design.
Wallace’s design included:
• 64 solar panels generating 2.5-million Btu per day.
• Four 125-gallon solar tanks.
• A 5-ton, water-to-water ground-source heat pump (GSHP) for hot or chilled water.
• 4- and 3-ton water-to-air GSHPs (which use the pool as a virtual ground loop).
• Two boilers.
• A pool and hot tub mechanical room.
• Energy recovery ventilators (ERVs) for the main house.
• Ventilation for the pool house.
• Radiant floor heating.
• A snow-melting system.
• Four heat exchangers.
• A 120-gallon domestic hot water (DHW) tank.
• Two 50-gallon tanks for the radiant system.
• A heat-extraction system that directly feeds the ground loop for the pool.
• A control system to integrate it all.
Wallace believes people can have all the energy-efficient systems built into a house that they can imagine, but if those systems are not controlled properly, they will not get the maximum efficiency of the complete system. “The overall energy efficiency of a house is the controls,” he said. “Controls are king. For example, if you’re putting in a high-end geothermal system and using controls from the 1950s, you’re losing a lot of the efficiency of the geo.”
While at a training class at Uponor in the spring of 2009, Wallace said he was introduced to the Climate CÅntrol™ Network System. “I was talking to the instructor about integrated controls for energy-efficient systems … I thought, ‘That’s what I’m looking for.’”
He sat down with Ray Blum, an Uponor rep with Dahl of Denver, to see what he could do with the system. “We started with just the heat pumps and the solar,” recalled Wallace. “Then we started adding more and more to the system. It was incredible what we could do with it.”
TOTAL CONTROL, MAX EFFICIENCYWhen it came to controlling the systems in and around his home, McTavish wanted more than just simple temperature set point change control. He wanted total control for maximum efficiency.
“Because we had so many parts, I wanted to make standard rules about at what temperatures certain things occur,” he said. “Given the solar resources and geo and natural-gas boiler, I wanted to determine when certain components go on and off, to make the system the most energy efficient.”
Because the control system is object-oriented, “we can make a change to any device based on the input of any other device.” For example, all the thermostats have up to nine possible set points, based on the current heat sources (solar, water-to-air heat pumps, or boiler).
In the winter, the solar arrays’ primary purpose is to heat the solar storage tanks. The water in the tanks directly heats the main house (via radiant floor heat) and indirectly heat the main home’s DHW. After solar is no longer active (because the sun is beyond a useful angle), the system continues to pull heat out of the four storage tanks for radiant floor heat and DHW.
Once the tanks’ temperatures drop to where they are no longer useful for radiant and DHW, the system changes the heat source for the house automatically to the water-to-air heat pumps, extracting heat out of the four solar storage tanks.
“The awesome advantage of dropping the tanks at that low temperature is that the next morning, as soon as the sun hits the solar panels, we already have enough temperature differential to start heating the four solar storage tanks,” he explained. “This allows us to switch from boiler mode to water-to-air heat pump mode (while we continue to raise the solar storage tank temperature). Once the tanks are hot enough, we change to solar mode and heat our radiant floor directly from the tanks.”
According to McTavish, even at currently low prices for natural gas, as long as the storage tanks are above 40°, it is more efficient to draw heat from the solar storage tanks than use the gas forced-air system.
When it comes to heating the pool, McTavish can use a combination of four options, depending on the heating demand and which is most energy efficient:
• Deck pavers with a hydronic radiant system underneath.
• Solar hot water panels.
• A 5-ton water-to-water GSHP, which runs against either the pond or heat-extraction pavers.
• Two other GSHPs (4- and a 3-ton water to airs) which use the pool as a virtual ground loop.
“In summertime, the heat pumps cool the house by dumping the heat to the pool,” explained Wallace. “That process is 800 percent efficient. For $1 of electricity, they are getting $4 of cooling in the house and $4 hot water heating in the pool. In the wintertime, the heat pumps can run directly against the solar hot water storage tanks to heat the house directly via the forced-air system. In the summertime, the heat pump runs against the pool gaining the 800 percent efficiency.”
CONTROL CONVENIENCEThe control system can do occupied and unoccupied mode “out of the box,” said Blum. “To further meet McTavish’s needs, we were able to add a vacation occupancy mode with a little extra programming.” When McTavish is away for extended periods, the system runs in vacation mode, which activates the solar to heat the house. Because the house is kept at 80° during the day, it never cools down to the 55° set point at night; the only energy expended to keep the house warm is from running a few circulators during the day.
The system also can be accessed remotely, so if vacation plans change, the user can extend or abbreviate the vacation mode. “McTavish was able to make changes to his system while on a different continent,” said Blum. “When he was in Africa on a mission trip, guests came to stay at the house and he was able to set the temperatures for the time the guests were there and change them back after they left.”
“Having Internet accessibility is the best feature of all,” said McTavish. “I look at my system on a daily basis, whether I’m at home or away. I look to see how hot the heat is coming off the solar panels, how long the boiler’s been running, observe the outside temperature, monitor the swimming pool temperature … it’s nice to be able to track that and see it in real time.”
BETTER THAN DDCAccording to Blum, who has commissioned seven Network Systems in the greater Denver area and has a background in DDC systems, it offers residential contractors several advantages over DDC. “Out of the box, it’s preprogrammed to do a bunch of different functions, and it’s completely customizable. A DDC is typically blank.”
“If we had to run all the McTavish programming from scratch,” said Blum, “it would have taken about four times the amount of time” it actually took.
The product’s “finished look” is another benefit as well. “It’s hard to get homeowners to spend money on things they don’t see,” he said. The system’s attractive graphics provide an attractive interface for the homeowner. “They really get to see what they’re paying for.”
Wallace agreed. “When you’re in a price war over a commodity, offering an integrated control package with a user-friendly interface can give contractors a competitive edge. I think consumers are looking for this kind of system; it would be in contractors’ best interest to learn more about total system integration controls. It’s not that hard to learn, yet it’s very powerful.”
Publication date: 01/10/2011