BY MARK EATHERTON
HYDRONIC HEATING AUTHORITY
THE NEW OWNERS of the barn intended it to be their last home ("The most unusual home I've ever worked on," April, pg. 46). They wanted to make sure that the home's heating costs were reasonable and wouldn't drain their savings account at the expense of comfort. They did their research and decided to settle on a ground-source heat pump to heat and cool their new home.
Enter Corey Merchant with Advanced Hydronics. He worked with the owners and designed the ground-source heat pump system that will provide the most efficient, least expensive operating costs for the new home.
In order to maintain a high degree of comfort, Corey chose to use non-electric thermostatic control valves. These valves have a track record of reliability and comfort from our hydronic grandfathers from across the Atlantic.
On a project of this scale, comfort is critical and these devices control the room's temperature within tenths of a degree of the set-point condition. It requires a much different approach in the design and installation of the near heat-source piping, but the benefits include extreme comfort and excellent thermal balancing and control. The use of either a pressure-activated bypass or a variable-speed circulator based on differential temperature or pressure is a must.
The location and positioning of the non-electric room temperature sensor is critical because the capillary tube that is an integral part of the controller is limited in length to 30 ft. We use flexible 3 /4-in. PVC tubing for a chase to maintain access for pulling the capillary tube after finished construction and maintaining access for possible future replacement, although we've never had occasion to replace one.
The main floor of the home was slated to have old weathered planks for its finished flooring. While this wouldn't usually pose a big problem for a typical house, this home's floor is the ceiling of the finished basement below, and the owners are retaining as much of the original interior finish as is possible. This would preclude the possibility of running the leaders for the radiant heating system through the joist bays of the floor.
The "joists" are 10 ft. on center. That was the standard of construction in the 19th century.
These floor planks would be shaved down and placed over the tops of 2-by-4 sleepers placed flat, 16 in. on center, which were placed on top of the oak purlins laid for the subfloor. The PEX tubing below the hardwood floors would be placed at 8 in. on center below the planking on top of 1 /2-in. XPS foam and covered in lightweight concrete. The home could be backed up with forced-air heat if the need arises, using the ductwork from the air conditioning system.
The master bedroom is on the main floor and was constructed as an addition to the original barn in such a way that it is virtually impossible to tell where the old barn ends and the addition begins. This area also has radiant floors but won't be covered with the old oak plank flooring.
The top floor of the "new" barn would hold two spare bedrooms for occasional guests. There is no second floor in the original part of the barn, so the living room has approximately 30-ft. tall ceilings. It's the perfect application for radiant floor heating.
Air conditioning, when needed, will be provided with a water-to-air heat pump with the capacity to heat water-to-water, if necessary. In total, there are 5 tons of water-to-air cooling capacity and 9 tons of water-to-water heating capacity with the cooling unit capable of being reversed and used as a heating unit. In addition to providing the space heating and cooling, the system will offer 120 gal. of ground-source heat pump preheated hot water, backed up by an auxiliary heating element.
The owners, in their continuing efforts to minimize their impact on the environment and to be stewards of the land, are considering the addition of a solar domestic hot water preheat system that will store its excess summer solar harvest in an underground, soil-based thermal storage system for use on their snow-melt system slated for installation on the north side of the home.
As you can well imagine, the 40-ft. tall barn casts a considerable shadow right on the garage and driveway of the home, which is on the basement level of the house on the north side. Without some means of snow melt, the area will have permafrost ice until the spring thaw.
The intent is to use the earth as a direct heat exchanger, not to quickly melt snow as it falls but to "assist" the snow in melting over a period of time. The owners hope to accomplish this without burning any fossil fuels in the process.
Stay tuned for more details on this Earth-friendly snow-melt system. Next month we will look at the details that went into a new barn built for a local equestrian center. Until then, happy barn storming hydronicing.
Mark Eatherton is a Denver-based hydronics contractor. He can be reached via e-mail at [email protected] or by phone at 303/778-7772.