WESTWOOD, MASS. — Last year, homeowner Lincoln Kaiser and a group of his neighbors in Westwood, Mass., persuaded NSTAR, the local gas utility, to put a natural gas supply line down his street. Once the fuel was available, the Kaiser family moved forward with a heating system retrofit. Out came the old oil burner, and in went a high-efficiency natural gas boiler.
“Our family has grown since we purchased the house,” said Kaiser. “We’d like to have a little more space, but don’t want to part with the home. Since we didn’t want to use any yard space for an addition, we decided to go up, not out.”
The 1,850 square-foot, ranch-style house went through a second-story addition this past fall, adding four new rooms. Although much of the mechanical system retrofit took place before the addition, the future connected load was taken into account. To read Part1 of the all-American retrofit article go to http://bit.ly/Owgq1q
Before the retrofit and addition, the home was heated using two zones of fin-tube baseboard connected to a 125,000 BTU boiler. Taco’s FloPro Designer software was used to calculate the existing heat load at 58,200 BTU/H, and with the extra load of the second story addition, the new system was designed to provide a total of 85,400 BTUs plus DHW. By doing a proper heat load analysis, even with the new square-footage, the new boiler is smaller than its predecessor.
The Kaisers wanted to abandon the fin-tube, preferring to heat the home with in-floor radiant. They quickly learned that this would require major changes to their near-boiler piping. While reluctant to have the whole system re-piped yet again, they held fast to their original desire to have an all-American boiler room.
When the oil-to-gas retrofit took place – months before work on the addition started – the new 105 MBH Burnham Alpine high-efficiency boiler was piped to accommodate a two-zone radiant system. Burnham boilers are built in Lancaster, Pa., and the company also has a foundry in Ohio.
But as walls went up, and their vision of the home became reality, the Kaisers realized that maybe two zones weren’t enough. They soon decided they wanted an ultimate comfort system. That meant more zones, web-enabled thermostats, and new components in the boiler room. They were also hoping the system could provide ultimate efficiency.
The Kaisers hired Mike Casey, of KC Plumbing & Heating, to re-pipe the boiler room according to the new design criteria, and to install the radiant system. Casey runs a one-man shop in Sharon, Mass., and specializes in subcontracting for builders. Homes under construction are his specialty.
Downstairs, the baseboard was removed and Watts Onix EPDM tubing was stapled into joist bays with access from the basement. “If it’s a staple-up job, I prefer EPDM tubing over PEX because of the flexibility,” said Casey. “It’s not like wrestling a python in tight quarters.” The staple-up portion is designed to use 140°F supply water. Watts’ wide product offering comes from numerous locations across the country, and the company recently opened a new foundry in New Hampshire to cast lead-free plumbing products.
A portion of the main floor is built over shallow crawlspace. Here, and across the entire upstairs addition, new Watts SmartTrac radiant panel system is installed over the OSB subfloor.
Made almost entirely of recycled material, SmartTrac offers all the benefits of a poured gypcrete slab, with less weight and thickness and no drying time. The system works with all floor coverings.
“The panels installed quickly, making them perfect for a roof-off project,” said general contractor Jim Kane. “After the material was down, Casey just had to walk 3/8-in. PEX or PERT into the grooves.” The SmartTrac portion of the system averages 125°F supply water.
Casey used a simple but effective means of supplying two temperatures. Between the system’s buffer tank and the five supply manifolds, a pair of three-way Taco iSeries mixing valves provides correct supply temperature. With a full-featured outdoor reset control built into the actuator, the valves modulate based on the outdoor temperature and the required supply temperature. That means year-round comfort control, efficiency and temperature delivery for every zone by supplying optimal water temperature.
Kaiser Home Project Video
Video about the Kaiser home project demonstrating the FloPro software in action
While the new wall-hung Alpine boiler wasn’t changed, the need to accommodate micro-zones, like individually-zoned bathrooms, meant that the near-boiler piping needed an overhaul. With a few clicks of the mouse, Casey was able to use the FloPro Designer software to reconfigure the piping and make provisions for the challenges that micro loads create.
If not dealt with properly, small heat loads mean the potential for boiler short-cycling. If supply and return water temperatures to a condensing boiler aren’t far enough apart, it won’t condense, meaning it’ll operate at traditional boiler efficiencies instead of the 95% AFUE that it’s designed for.
To avoid this, a 30-gallon Boiler Buddy buffer tank, made in southern Wisconsin, was piped between the boiler and manifolds. Its thermal mass can satisfy some of the smaller calls for heat without the need to fire the boiler. It also extends the input cycle of the boiler whenever it does fire.
While tiny zones increase comfort and controllability, they present another challenge beyond boiler short cycling: over pumping. The system needed pumps that could accommodate a widely-varying GPM demand. Casey installed an ECM-driven, variable-speed Taco Bumblebee circulator after each iSeries Mixing Valve.
“We’re going to great lengths to achieve the highest level of efficiency possible,” said Casey. “By not installing delta-T, variable speed pumps, we’d be missing out on both electric and fuel savings. The iSeries mixing vales provides the optimal water temperature, and delta-T Bumble Bee pumps provide the perfect flow rate, by maintaining the designed-for 20°F delta-T in the zones.” Taco’s pumps and hydronic components are manufactured in Cranston, R.I.
The Alpine boiler provides DHW through the use of a 60-gallon indirect water heater. A new Taco direct-mount mixing valve ensures safe delivery temperature. With the tank temperature raised, the easily-installed mixing valve also extends the amount of available hot water without increasing tank size. This allowed the Kaisers to add a bathroom upstairs without buying a bigger tank.
Stretching comfort, efficiency
In Massachusetts, towns can remain on the state’s base energy code or adopt the Stretch Appendix to the Building Energy Code as their energy code requirement, which means achieving approximately 20% better energy efficiency in new buildings. While the stretch code was adopted in Westwood, Kaisers’ goal to reduce their environmental impact paralleled their comfort initiative, so hot water recirculation was a must-have.
Taco’s SmartPlus hot water recirc system was installed during the retrofit. The pump “learns” the family’s water use patterns This not only keeps hot water at the tap for use at a moment’s notice, but the average family of four, like theirs, can save 12,000 gallons of fresh water each year. But recirc pumps aren’t the only adaptive technology used at Kaisers’.
“Like most families with young kids, we’re pretty tech-savvy,” said Kaiser. “We wanted precise control of the climate in the house regardless of where we are.”
To aid in reaching their “ultimate comfort and efficiency” goal, almost every room in the house is individually controlled by web-enabled ecobee Smart thermostats. This offers them comfort while they’re home, and energy saving’s when they’re not.
Kaisers can manually input setpoint for times and days of the week, or use the Smart t-stat’s calendar. Either way, the result is optimum comfort and efficiency because overtime the system “learns” how the home performs, then optimizes for comfort and savings. Ecobee products come out of the box ready to connect to the home’s Wi-Fi, just like a phone or tablet, and there’s no monthly or annual fee.
For the installer, the remote-access T-stats make maintaining the relationship with the homeowner easier. If desired, installer contact info can be programmed into T-stat so that if the homeowner gets an alert, the name and number of the company is displayed.
Work at the Kaiser home nears completion. This past winter they dealt with the inconvenience of a renovation project in progress. But next winter, Lincoln Kaiser and his family say they look forward to a radiant and DHW system built around maximum efficiency and comfort.