The Retrofit Of All Retrofits
Aspen SolarThis radiant retrofit started with the contractor calling Aspen Solar to design the solar snowmelt/DHW/ radiant floor heat system.
"The house was an energy sieve, and was crying for a retrofit," says Mike Tierney of Aspen Solar in Aspen, Colo. The 1970s residence was built with minimal wall and ceiling insulation, R11 and R19 respectively. "In Pitkin County there are strict codes on snowmelt usage, and with solar the client can expand his snowmelt square footage."
The existing heating system used a 500,000-Btu cast iron boiler with three zones and a 75-gallon direct-fired water heater. There was no snowmelt and all heat was convectors.
The Aspen Solar heating system consists of one Monitor Products MZ 40C natural gas 142,000-Btu fully condensing, 95 percent efficient, sealed combustion boiler. This boiler was chosen because of the high efficiency needed by the local building codes. There are nine high temperature heat zones, three low-temperature heat zones and one indirect fired water heater zone.
Domestic Hot Water has priority, zoned by a Taco 0011 pump and controlled by a Taco 501. The radiant infloor slab Kitec tubing and staple up tubing with Radiant Tech plates low temperature systems are zoned with Taco zone valves, Taco 008 pump, and controlled by a Taco 403 zone valve control box. The high temperature heat zones use Haydon convectors, kick space heaters, Hide a Base heaters, and Buderus Towel racks. A differential pressure bypass valve is used on the main header system. Air-sensing thermostats are used as the zone thermostats. The MZ 40C uses a two-stage burner for increased efficiency.
The snowmelt system also uses an MZ 40C for the heat source. There are four zones of snowmelt; all are zoned with pumps. An ETI snowmelt sensor and a tekmar 362 control the pumps. This tekmar control uses the outdoor temperature along with other sensors to control the secondary loop temperature. This is done by primary/secondary plumbing and variable speed injection pumping.
The snowmelt system changes between idle and melt mode depending on the different sensor inputs. The MZ 40C is the perfect boiler for this low temperature system.
Unique to this house is the use of a tram that connects the garage to the main entry. This is used for groceries, large loads, ski gear, etc. Both landings of the tram and the tram concrete pathway are snowmelted. The 5/8-inch Kitec tubing is embedded in concrete with slab stones on top.
Approximately 1,200-sq. ft. of space is snowmelted. The most critical areas are the steep north-facing stone stairs leading from the garage to the entrance and the tram way.
"The house now as R24 walls and R40 ceilings, better windows and uses three Heliodyne 4- by 8-ft. solar thermal collectors," Tierney beams. These solar collectors heat up both an 80-gallon solar storage tank and the 79-gallon Buderus tank for domestic hot water.
"This house has nine different levels, uses towel racks, convectors, kickspace heaters, hide a base infloor radiant heaters, aluminum heat retention plates, radiant tubing embedded in gypsum and concrete, and uses a 95 percent efficient boiler." The snowmelt is embedded in concrete and stone and was laid in a new age pattern leading to the hot tub and kitchen deck areas, done primarily because the owner was limited on snowmelt square footage and could not snowmelt the whole area.
"This was a retrofit of all retrofits. Aspen Solar was truly tested on this project, and both the owner and builder are very happy with the system's performance and the clean boiler room."
Radiant Specialties Inc.
Blue Ridge Radiant Systems