These days, Pueblo, CO, is recognized for its vibrancy, eclectic art, food, and growth. It’s also one of the most fascinating historical towns in America—all attributes that make Pueblo and its suburb Walsenburg an attractive place to live.
Among other things, the steadily growing economy ensures ample building and construction work. Out of town, the surrounding mountainsides are dotted with high-end homes, many with in-floor heat—the prevue of specialized plumbing and hydronic pros.
Most of the distinctive homes outside Pueblo are unique in some way, either through architectural ingenuity or building-owner eccentricity.
Yet others are unique in their sustainability. Though this home is larger than most, its small carbon footprint belies its size. And while it is a residential example, the technology and design are suitable for commercial and industrial applications as well.
The design process began in January of 2015, when the owners gave all of their ideas, needs, and stipulations to the professionals at Pueblo-based general contractor (GC), Pioneer West Homes.
The sprawling floor plan is primarily single-story with grand ceiling heights, though two second-story suites are included on opposite sides of the home. Concrete construction with foam insulation and high-end windows provide a tight building envelope.
Ultimately, the plan was to make the home as energy efficient as possible. With that goal confirmed emphatically by the homeowners, the next need was to find a mechanical systems installer who would be able to bring their dream into reality.
After weeks of searching, the general contractor and homeowners chose Flow Right Plumbing, Heating, and Irrigation to work with them on the project. Flow Right’s founder, Lance Harvey, combined his father’s irrigation company with his own plumbing company eight years ago.
The wide variety of work, big territory, and the company’s reputation for designing and installing intricate hydronic systems usually leads to several unique applications each year. Most recently, they were contacted about an all-electric radiant system for a new home 125 miles south of the Flow Right shop.
“Designing a hydronic radiant system for premium comfort and efficiency isn’t hard when your heat source is propane, gas, or oil,” says Mike Merryman, hydronic division manager at Flow Right. “It’s a bit trickier to meet both those requirements with an electric heat source. We needed to carefully consider each component and the way we were installing all of them.”
Tight Building Envelope
The plan was to use a lightweight concrete slab and 12,000 lineal feet of PEX to handle the home’s heat load based on a design temp of -10°F. This allowed Flow Right to provide substantial thermal mass despite the fact that the entire structure was built over a crawlspace. Even with PEX on 9-inch centers and relatively low supply temperatures, the system provides a very consistent floor temperature and high comfort levels.
Thermal mass was the name of the game when it came time to select a heat source. Instead of using standard electric boilers, they opted for two large off-peak, electric-thermal storage units which “charge” overnight when the local San Isabel Electric Association offers an off-peak discount.
The last, but arguably most critical, piece of the puzzle was how to circulate water accurately and efficiently.
“We needed an ECM circulator as the main system pump for its ability to supply precise flow rates—exactly variable to system demand,” says Merryman. “With a well-insulated home like this, and Colorado’s big temperature swings, it would be far too easy to overshoot the slab and turn the whole house into a sauna. The pumps were selected for comfort first, then efficiency.”
The main system pump, which feeds nine zones, is joined by smaller ECM circulators on each of the two boilers. While the energy needed to move heat is small in comparison to the power needed to create heat, ECM motors provide up to 85% energy savings over a conventional (PSC motor) circulator.
Last October brought the first Flow Right crews to the job site. While the plumbing division started rough-ins, the hydronic techs were laying half-inch Mr. PEX tubing, soon to be covered in a self-leveling gyp-crete. Snow and mud became a huge obstacle for the duration of the project, often halting progress altogether.
In the mechanical room, near-boiler piping was prepared while PEX was going down. A single Taco VR3452 high-efficiency circulator was specified to provide flow for all nine radiant zones. The pump can operate from anywhere between 10–180 watts, so whether one zone or all nine are calling, the correct amount of heat goes out to the system.
“Our smallest zone is only 190 feet of tubing,” says Merryman. “So we needed a pump that could drop really low while also pumping the whole house in the dead of winter. Plus, we needed the option of adding a few more zones in the near future, whether that be an indirect water heater, snowmelt for the courtyard, or unit heaters in the garage.”
Flow Right kept the VR3452 (34 feet of head, 52 GPM) in automatic mode, though it has three other modes and night setback for a variety of applications. The light-commercial circulator has an LED readout and industry-standard flange width. An optional communication module provides Ethernet communication and Modbus RTU communication, and allows for simple twin-pump installation if redundancy is needed.
The distribution system includes a large set of manifolds, with each zone actuated by a 3/4-inch Taco Zone Sentry zone valve. This manifold feeds remote, 1/2-inch injection manifolds throughout the home.
The Steffes boilers—or electric thermal storage devices, as the manufacturer calls them—are piped together and run in unison at all times.
“Putting the electric units in was a unique experience,” says Luke Drummond, Flow Right technician. “First, you set the super-insulated shell, then you stack it full of ceramic bricks.”
The larger of the two off-peak units in the mechanical room is rated at 45.6 kilowatts, and it will provide 65–110 MBH throughout the course of a day, based on a 12-hour charge cycle. The smaller unit can provide approximately 50 to 75 MBH.
“During off-peak hours, typically overnight, the home’s electric meter signals the units to charge,” says Jim Dechert, VP of solutions and automation at Steffes Corporation. “Electric elements heat the bricks and surrounding air inside the units to more than 1,250°F. A fan at the bottom of the cabinet forces air through an air-to-water heat exchanger, with the radiant system as the heat sink.”
The units store the heat and run only as needed. When the fan runs, so does the Taco 007e boiler pump, sending heat to the system’s primary loop.
“We installed 007e circulators on the boilers because, at this distance from the shop, we wanted the dependability of the 007,” says Hydronic Technician Derek Leveque. “But, with our need to cut every watt of power consumption out of the installation, we chose the new ECM version.”
An outdoor reset control is included on the thermal storage units. Much like a conventional boiler, the outdoor sensor modulates the fan speed in order to provide the correct supply water temperature. In addition, the length of the boilers’ charge cycle depends on the outdoor temperature; outdoor ambient determines how hot the bricks become.
“The bricks carry a tenfold thermal storage advantage over water,” says Deichert. “The same brick is used across our various hot water and hot air furnace lines. It’s a mixture of iron and clay, pressed and baked into a durable, stackable form.”
A 20°F Delta T was used for the radiant system. Ironically, that’s as good a number for the off-peak units as it would be for a condensing boiler. With the home’s gyp-crete slab, cycles are long and few, though when outdoor conditions drop to design temp, circulation is nearly constant.
“The circulators can obviously run all day, but they don’t draw much power,” said Merryman. “Most of the energy is consumed when power is at a 50% discount. The result is full-time comfort with part-time expense.”
After battling the elements through the winter, Flow Right finished work at the remote home in May.
But conversations with the customer about solar thermal and photovoltaic hinted at several return trips. No sweat, it’s only 125 miles.