Patent Publication Number: US-2007108307-A1

Title: Temperature conditioning radiant wall system for buildings

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is a continuation-in-part of co-pending US application 10/851,349 entitled “MULTI-STORY WATER DISTRIBUTION SYSTEM” and which was filed May 21, 2004, the entirety of which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates to systems for the heating and cooling of buildings, reduction in capital expense, and the distribution of water for minimizing the number of piping risers and avoiding over-pressure supplies through the strategic placement of pressure reducing valves.  
     BACKGROUND OF THE INVENTION  
      Heating and cooling systems for multi-story buildings typically use specifically supplied and circulated hot and cold water for delivery to heat exchangers. Traditionally, room-by-room heating, and air conditioning systems in large buildings have been, what are known in the art, as four-pipe fan-coil systems; two pipes for chilled water flow, and two pipes for heated water flow. Individual fan-coil units placed at various locations throughout the building provide for zonal temperature control. Heating or cooling is provided by having the fan circulate air over a coil that is accessing either the hot or the chilled-water piping system, respectively. Water distribution systems for multi-story buildings also typically comprise various arrangements of water supply and returns.  
      Conventional  8  floor zones extend risers up through all suites with the associated water noise for the lower suites and the large number of risers. Each riser is associated with fire blocking and challenges at bulkheads and cross-over floors.  
      To date, choices for heating and cooling commercial or multi-suite buildings have been limited and equipment such as fan coils are an expensive, but known, solution.  
      Multi-story buildings further introduce challenges including problems related to hydrostatic pressure variation from floor to floor. In a 24 storey building the pressure at the lowest floor may be about 130 psig so as to maintain 40 psig at the highest of the upper floors or roof where the hydraulic head is at its minimum. To supply a  72  storey building from a single water supply riser would result in pressures at the lowest floor at about 250 psi. However, it is unacceptable to apply 250 psi or even 130 psig water for domestic use. Higher pressure in a domestic hot water system will ensure return flow to the hot water boilers but such pressures are too high for domestic purposes.  
      There is a need for a reduction in redundant piping, elimination of noise in suites, lower capital cost and more efficient systems in the heating, cooling and distribution of domestic water in high rise buildings. Applicant addresses these shortcomings and incorporates further improvements to heating and cooling systems, some of which can be incorporated with domestic water distribution.  
     SUMMARY OF THE INVENTION  
      Applicant has provided a system which significantly reduces the piping needed to supply domestic hot and cold water to one or more units, residences or suites in high rise buildings, solves issues associated with the supply of water at pressures above desired domestic use pressures, and incorporates novel heating concepts for multi-residence buildings. The number of risers throughout can be reduced in number by more than an order of magnitude. Noise issues associated with flow in risers extending through each suite is eliminated.  
      Applicant has recognizes that use of domestic water system for heating and cooling using partitioning walls as radiant walls, enables heating and cooling of adjacent rooms and better utilizes existing domestic water systems for minimizing capital expenditures such as through the reduction or elimination of fan-coil or hydronic radiant panel devices.  
      The partitioning walls condition room temperatures by acting as a cold or hot radiant wall either using hot domestic water for heating, or using chilled domestic water for cooling, or alternating therebetween using thermostatic valves for circulating either the heated domestic water or chilled domestic water.  
      Applicant further recognized that several aspects of pressure control at lower floors provides significant advantages. Use of full pressure, variable over elevation, domestic cold and hot water systems and pressure reducing valves as required for domestic service only, eliminates floor to floor risers and remarkably reduces the numbers of piping runs. Pressure and flow control is maintained despite the number of floors in the building. No longer do domestic water pressure and plumbing fixture requirements limit the use of common risers at full pump pressure at full hydrostatic head. Further, the system has several solutions for ensuring hot water availability and avoiding stagnation which can occur in some domestic lines, contrary to public safety and contrary to plumbing regulations in some jurisdictions.  
      In one embodiment, the system has a domestic hot water supply riser and a hot water return riser. At each serviced floor, a domestic hot water distribution main extends from the hot water supply riser to each of one or more suites and returns to the hot water return riser. On each floor, typically lower floors, at which a riser pressure is higher than preferred service pressure for domestic plumbing fixtures, a pressure reducing valve is situated at least between the distribution main and domestic use fixtures in the suites for reducing the pressure of the cold and the hot water as required. Coupling of the heating systems directly off of the supply riser at full water pressure and to the hot water distribution main provides an effective piping system for circulation of hot water through heating systems and allows for return of hot water circulation to the heating system without a need for further pumping. Further, implementation of a substantially constant circulation of hot water through the hot water distribution main ensures hot water is available on demand. Additionally, when heating is not required, regular and periodic circulation through the hot water distribution main avoids stagnation of the domestic hot water supply.  
      As a result, applicant has determined that up to 70% can be saved on the fluid piping in a building and  20 % on the cost of the entire mechanical system. Supply risers no longer run through suites, eliminating noise. Bulkheads and cross-over floors are no longer a concern for domestic water distribution. Water circulation is simplified without a need for auxiliary pumps to return spent water to heating and cooling systems. With reduced numbers of risers comes less wasted floor area for accommodating piping. Use of domestic hot water for heating, and as desired domestic cold water for cooling reduced capital cost by reducing or eliminating fan coils and other equipment.  
      In one broad aspect, a system for temperature conditioning multiple serviced floors of a high rise building is provided, each floor having one or more suites having interior and exterior walls and having plumbing fixtures being serviced with at least domestic hot water. Such a system comprises: providing at least a domestic hot water distribution main at a supply pressure at each serviced floor for servicing the suites. The domestic hot water distribution main provides domestic hot water to one or more suites on the floor. The domestic hot water is thermostatically controlled through radiant tubing installed in one or more radiant walls in a suite, of one or more suites, for heating the suite. For each floor at which the supply pressure of the domestic hot water is above a first pressure threshold, typically a suitable domestic service pressure, the water pressure of the hot water to the domestic use fixtures is reduced to about the first threshold pressure using one or more pressure reducing valves situated between the distribution main and the domestic use fixtures of each suite.  
      Preferably, the system further comprises a domestic cold water distribution main for each serviced floor at a supply pressure. In embodiments where cooling is not required, such as in moderate climates, and for each floor at which the supply pressure of the domestic cold water supply at each floor is above a second pressure threshold, typically the suitable domestic service pressure, the water pressure of the cold water is simply reduced at the before the distribution main. Where cooling using domestic cold water is employed as well for the radiant walls, one can maintain the domestic cold water distribution main at full pressure for radiant wall circulation and, as applied to the domestic hot water, reduce the water pressure of the cold water to the domestic use fixtures to the second threshold pressure using one or more pressure reducing valves situate between the full pressure cold water distribution main and the domestic use fixtures of each suite.  
      Preferably, a heating system or heater provides heated hot water to each domestic hot water distribution main, and a hot water return riser returns hot water from the distribution mains to the heater. Similarly, a cold water riser provides chilled cold water from a cooling system or chiller to each floor&#39;s distribution main, and a cold water return riser returns cold water from each distribution main to the chiller.  
      For heating and cooling using radiant walls, a pair of three-way valves are employed, a first three-way valve controls whether chilled or heated domestic water is circulated into the tubing in the radiant wall, and a second three-way valve controls whether the thermally spent water returning from the radiant wall is returned to the cold water return riser or the hot water return riser respectively.  
      Preferably the domestic hot water main is fit with a flow control valve to flow back to the return riser so as to provide a controlled, yet substantially constant flow of hot water for ensuring a substantially on-demand hot water response at the domestic use fixtures. Preferably the flow control valve is positioned between the distribution main after the last serviced suite, and a return main to the return riser. The radiant walls and other heating loops can be provided with thermostatically controlled valves having periodic dump features to avoid stagnation.  
      Typically radiant wall are provided on interior walls of a suite for bi-directional heating. More preferably, suites adjacent an exterior wall, and similarly adjacent utility or common areas such as stairwells, can be provided with additional radiant tubing installed in the floor such as adjacent the exterior wall. As necessary, walls between adjacent suites can be fit with radiant walls, but are arranged for unidirectional heating to the suite having the thermostatic control.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic plan view of an arrangement of a hot wall heating system arranged in an intervening partition wall dividing two rooms of a suite;  
       FIG. 2  is a schematic elevation view of radiant tubing arranged in a radiant wall and operating at full hot water supply pressures;  
       FIG. 3A  is a schematic elevation of a high rise building implementing some of the heating and cooling features of the present invention;  
       FIG. 3B  is a schematic elevation of a high rise building implementing only heating features of the present invention;  
       FIG. 3C  is a schematic of adjacent suites of a lower floor according to  FIG. 3A  and illustrating the hot and cold water distribution mains and pressure reducing valves to fixtures;  
       FIG. 4  is a schematic plan view of an arrangement of a hot wall heating system arranged on the facing wall of a single suite to avoid heat transfer or loss through the facing wall, such as to an adjacent suite or non-suite;  
       FIG. 5  is a schematic plan view of an arrangement of a hot wall heating system arranged in an intervening partition wall dividing two suites where one of the two suites is adjacent an exterior wall and the radiant tubing is expanded to include auxiliary floor heating; and  
       FIGS. 6A and 6B  illustrate the domestic hot water and domestic cold water piping to typical plumbing fixtures in a suite.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      Generally, as shown in  FIG. 1 , adjacent rooms  10   a , 10   b  within a suite  11  are separated by a walls  12 , such as an interior partitioning wall  13 . During seasons where the rooms  10   a , 10   b  require heating, one or more of the walls  12  can be operated as hot radiant walls  20 . In the case of an interior partitioning wall  13  operated as a radiant wall  20 , heat radiates bi-directionally into the suite  11  in both directions to adjacent rooms  10   a , 10   b . An interior partitioning wall  13  within a suite  11  is a convenient embodiment for a bi-directional radiant wall  20  wherein a suite occupant can control the radiant output solely for their suite  11 . One is less inclined to operate a party wall  14 , located between adjacent suites  11   a,   11   b,  as a bidirectional radiant wall  20  because thermostatic control by an occupant in one suite  11  a can also affect the comfort of an occupant of the adjacent suite  11   b . Options include either avoiding the implementation of radiant walls  20  in a party wall between suites  11   a , 11   b  or instead to configure such radiant walls  20  for unidirectional radiant thermal control.  
      While referred to as a “radiant” wall, which suggests radiant heat transfer, other aspects of the principles of heat transfer are also inherent and contemplated, such as conduction to the wall surface and convection therefrom. Further, radiant walls  20  can provide thermal control including either heating and cooling. While examples are provided in terms of a hot radiant wall  20 , heated using domestic hot water DHW, temperature conditioning or thermal control using a radiant wall  20  can equally include cooling using a circulation of domestic cold water DCW. Temperature adjusted water, which is circulated through radiant walls  20  for temperature control, is generally termed herein as thermal water and more specifically as domestic cold water DCW or domestic hot water DHW.  
      With reference also to  FIG. 2 , the radiant wall  20  comprises thermal tubing  21 , such as cross-linked polyethylene tubing (PEX), for example AQUAPEX® available from Wirsbo Company of 4925 W 148th Street, Apple Valley Minn., 55124, USA, located within the cavity of the partition wall  13 . The tubing  21  is arranged in a serpentine manner to distribute the tubing in the wall. The tubing  21  can be overlapped as necessary and without concern. Tubing  21  can be arranged in up-and-down orientation (not shown) or a side-to-side orientation (shown) which can have advantages if the system needs to be drained at come point. Thermal water is circulated through the tubing  21  as necessary to meet the thermal loads, typically heating and can alternately include cooling. Heating loads for each suite  11   a , 11   b  . . . are provided from the domestic hot water DHW provided at each floor. Where necessary, cooling loads are provided from the domestic cold water DCW, preferably chilled, provided at each floor. The length of thermal tubing  21  fit to the radiant wall  20  provides sufficient surface area to meet the design thermal loads as is known to those of skill in the art.  
      Within a radiant wall  20 , the thermal tubing  21  is positioned sufficiently offset within the wall  20  from either wall surface to avoid accidental punctures from screws and other fasteners.  
      An implementation of various embodiments in the context of a high rise building  30  is set forth in  FIGS. 3A-3C  and discussed later below.  
      With respect to the radiant walls  20 , and in  FIG. 4 , where heating is desired only to one side of the radiant wall  20 , such as at a party wall  14 , the wall  20  is configured for directing the heat H into the room  10  only which is to be heated. Again, the thermal tubing  21  is also positioned sufficiently offset within the wall  11  from the wall surface to avoid accidental punctures from screws and the like, however, heat transmission is emphasized from one side of the wall  20 , either through heat reflective surfaces, offsetting the radiant tubing  21  more towards the wall surface adjacent the room to be heated, or through selective insulation  15  or a combination thereof.  
      In  FIG. 5 , end suites are subject to greater heat loss through windows and an additional exterior wall and can be fit with additional thermal tubing  21 , such as in an auxiliary radiant heating loop  22 . The loops  22  are embedded in the floor and provide heat H adjacent the areas most susceptible to the additional heat loss or gain due to exterior influences. The loop  22  can be in plumbed to circulate in series with radiant wall  20 , such as after the thermal tubing  21  has passed through the radiant wall and resulting in lesser thermal gradient. Depending on the plumbing arrangement, alternatively the loop  22  can be plumbed in parallel with the radiant wall for maximal output of heat H.  
      Domestic hot water DHW and domestic cold water DCW are also typically provided at each floor of a multi-story building and are circulated to each suite  11 .  
       FIG. 3A  is a schematic illustration of a typical arrangement of piping for radiant walls  20  for a high rise, multi-story building  30 . At least a heating system  31  such as a boiler or heat pump is provided for the heating and circulation of heated domestic hot water DHW through a hot water supply riser HWS to each floor  33 . Domestic hot water returns to the heating system  31  through a hot water return riser HWR. The heating system can be located at a convenient location. Hot water heaters and boilers with heat exchangers for heating domestic hot water are often at roof level. Heat pumps, which can heat or cool domestic water are typically located in the basement levels adjacent ground loops.  
      The hot water supply riser HWS and hot water return riser HWR extend to each of the multiple services floors  33  and are fluidly connected to the hot water heating system  31 . Water pressure of the domestic hot water DHW in the risers HWS,HWR varies with elevation due to the variation in hydrostatic head.  
      The heating system  31  is illustrated at the top floor but could be located at any elevation in fluid communication with the supply and return risers HWS,HWR.  
      Further, on very tall buildings, vertical zones of multiple floors can be provided with their own heater, hot water supply and return risers (not shown). The multiple serviced floors can be arranged in vertical zones, further comprising for each zone a booster pump which supplies water to the zonal hot and cold water risers to ensure a pressure exists therein which, at a highest floor of the zone is at least domestic service pressure, and at the lowest floor of the zone, is at or below a maximum booster system pressure.  
      Where cooling functions are desired, a cooling system  41  such as a heat pump or chiller is also provided for circulation of chilled domestic cold water DCW through a chilled water supply riser CWS to each floor  33 . Domestic cold water returns to the cooling system  41  through a chiller water return riser CWR. The cooling system  41  is illustrated at the top floor but could be located at any elevation along the supply and return risers CWS,CWR. Water pressure of the domestic cold water in the risers CWS,CWR varies with elevation. The temperature of the chilled water is pre-determined to avoid condensation issues as is known to those skilled in the art.  
      With reference to  FIGS. 3A and 3C , each serviced floor  33  comprises a plurality of suites  11   a,   11   b  . . . serviced with domestic cold water DCW and domestic hot water DHW, supplied by the hot water distribution main HWM and cold water distribution main CWM respectively. For illustrative purposes only, one suite  11   a  is shown plumbed to the mains HWM,CWM. Further, for illustrative purposes only, a pedestal sink  44  is provided in suite  11   a  as an example of a domestic use fixture  42 .  
      Characteristic of multi-story buildings  30 , each successive higher floor  33  experiences a corresponding loss of hydrostatic head and water pressure. In order to provide water under sufficient domestic service pressure P D  to more than one vertically arranged floor in the building, the hot water supply riser HWS is pressurized, at lowest of the lower floors  33   b , to a pressure threshold P H , which is often greater than the desired domestic use pressure P D , so that a minimum domestic pressure P L  can be maintained at a highest of the upper floors  33   t . The pressure threshold P H  at the lowest of the lower floors  33   b , is typically at a pump pressure for delivering at least the minimum domestic pressure P L  to the upper floors  33   t.    
      Similarly, the cold water supply riser CWS also extends either up or down the building  30 , and is subject to the same variation in hydrostatic head and will operate at substantially the same variable pressures. Accordingly, the lowest floors  33   b  are supplied at the greatest pressure with water pressure diminishing at higher elevations to the upper floors  33   t  which are supplied at the lowest pressure P L .  
      Domestic facilities or fixtures  42 , such as toilets, sinks and laundry hook-ups have a maximum service pressure and preferably operate at domestic service pressures P D . The fixtures plumbed with domestic water will a preferred hot water threshold pressure and a cold water threshold pressure. Usually the threshold pressures for the DCW and DHC at the fixtures  42  is the same domestic service pressure PD. As shown in  FIGS. 6A and 6B  typical plumbing fixtures in a suite include a water closet or toilet WC (DWC only), laundry L (DHW and DCW), shower SH (DHW and DCW) and a sink SK (DHW and DCW).  
      The pressure of the domestic hot water DHW and domestic cold water DCW in the risers HWS,CWS at lower floors  33   b  can be higher that acceptable domestic service pressures P D . Accordingly, the cold water DCW and the hot water DHW for these lower floors  33   b  are pressure reduced at the fixtures  42 . One or more hot water pressure reducing valve  43  are at least provided at each suite  11  for reducing the pressure of the hot water DHW directed to plumbing fixtures  42 . The valve  43  is located between the hot water distribution main HWM, which circulates heating water at full riser pressure through radiant walls  20 , and the fixtures  42 , which are fed at reduced domestic service pressures P D .  
      Upper floors  33   t  do not require pressure reduction as the water pressure is already between the minimum pressure P L  and a preferred domestic service pressure P D . Accordingly, the domestic plumbing fixtures  42  for upper floors  33   t  are directly plumbed to the distribution main HWM at the full pressure of the hot water supply riser HWS.  
      Further, in  FIG. 6B , before the water returns from a serviced floor  33 , a thermal tubing  21  from the hot water distribution main HWM can also be directed to ancillary, non-suite areas such as stairwells  50 . In this arrangement shown in  FIGS. 6A and 6B , and according to  FIG. 3B  in which cooling is not required, the domestic cold water DCW is not circulated. Therefore, a pressure reducing valve  43  need only be provided (not shown) between the cold water supply riser CWS and the cold water distribution main CWM as domestic cold water is only used for domestic use fixtures  42 . Accordingly, pressure reducing valves are not needed, nor illustrated, between the cold water distribution main CWM and a return riser, as there is no need for a cold water return main or riser.  
      As discussed in co-pending application Ser. No. 10/851,349, filed May 21, 2004 to Applicant, the entirety of which is incorporated herein by reference, and discussed in the context of the use of fan coils as the preferred heating and cooling equipment, improved efficiencies and comfort are achieved using an improved piping system by implementing hot water supply risers HWS and hot water return risers HWR extending vertically up the building with pressure reduction applied on a floor-by-floor basis as necessary to accommodate domestic plumbing fixtures  42 . Each floor is supplied with a domestic hot water distribution main HWM for providing domestic hot water service throughout the floor to each suite  11 . Even at the lower floors  33   b , hot water recirculates at full hydrostatic pressures between the hot water heating system  31  or boiler, the supply risers HWS, and each distribution main HWM, so as to enable recirculation of return domestic hot water DHW through the hot water return riser HWR to the hot water heating system  31 , the recirculation being performed without pumping. Therefore, on each lower floor  33   b , a plurality of hot water pressure reducing valves  43  are provided, one at each suite  11  or for one or more of the plumbing fixtures  42 . Each pressure reducing valve  43  reduces the pressure between the full pressure of the hot water main HWM and the actual domestic use fixtures  42  at domestic service pressures PD. At upper floors  33   t , once the hydrostatic pressure in the hot and cold water supply risers HWS, CWS reduces to approximately 80-85 psig or less, pressure reducing valves  43  on both hot and cold water respectively are no longer required.  
      As shown in  FIG. 3B , in instances where cooling is not required, the cooling system  41  for the domestic cold water DCW is generally not required at all, and the domestic cold water DCW can be pressure reduced with valves  43  at each lower floor  33   b  and a cold water distribution main CWM for each lower floor  33   b  can operate at domestic service pressures PD.  
      Returning to  FIG. 3A , where cooling through radiant walls  20  is also an option, the cold water supply riser CWS supplies cold water to a cold water distribution main CWM for circulation of cold water to each suite on the floor  33 . Again, for lower floors  33   b , pressure reducing valves  43  are provided between the cold water distribution main CWM and the domestic use fixtures  42 .  
      With reference also to  FIG. 3C , domestic hot water and domestic cold water is provided to radiant walls  20  in two adjacent suites  11   a,   11   b  through the hot water distribution main HWM and cold water distribution main CWM respectively. The two suites  11  shown are located adjacent an end of a run of the distribution mains HWM,CWM. In order to implement alternative heating or cooling through the radiant walls  20 , a first three way valve  45  is provided for alternately connecting an inlet end of the thermal tubing to the hot water distribution main HWM for heating the radiant wall  20  and the cold water distribution main CWM for cooling the radiant wall. Under thermostatic control, either hot water DHW flows through the thermal tubing  21 , or chilled water flows through the thermal tubing  21 . The thermally spent water flows out a discharge end of the thermal tubing  21  for return to one of the risers HWR,CWR. Preferably a second three way valve  46  alternately connects the discharge end of the thermal tubing to the hot water return main HWRM while heating, and the cold water return main CWRM while cooling. Both the first and second three-way valves  45 , 46  can be controlled by a conventional thermostatic controller (not shown).  
      Circulation of hot water through the radiant walls  20  is effective by directing hot water DHW to each radiant wall  20  from the hot water distribution main HWM, and back to a collector main or hot water return main HWRM. Generally the hot water return main is arranged in a run parallel to the distribution main HWM and is in fluid communication with the hot water return riser. The hot water return main HWRM collects all the spent hot water collected from the radiant walls  20  for return to the hot water return riser HWR and the hot water heating system  31 .  
      After having distributed hot water to all suites  11  on a floor  33 , it is also preferable to install a flow control valve  47  between the hot water distribution main HWM and the return riser HWR. Preferably the flow control valve  47  is positioned between the hot water distribution main HWM, at about a last suite of the one or more suites in series, and the hot water return main HWRM. The valve  47  can be set at about ½ USgpm to assure that there is a continual flow and supply of domestic hot water in the distribution main HWM on each floor and adjacent each suite  11 . This is important, especially in the summer months when no hot water is being used for circulation through the radiant walls  20 , so as to provide hot water on demand to the fixtures  42 . More preferably (not shown), in the case of very large residential suites, a flow control valve can be located (not shown) in each suite to assure that the hot water reaches the suite&#39;s faucets in less time.  
      As shown in  FIG. 3C , radiant walls  20  are both heated and cooled. Pressure reducing valves  43  are positioned, in each suite  11   a,   11   b,  between the mains HWM,CWM and the fixtures  42  for the particular suite  11 . Accordingly, pressures need not be reduced for use with the radiant wall  20 .  
      Circulation of cold water through the radiant walls  20  is effective by directing cold water to each radiant wall  20  from the cold water distribution main CWM, and back to a collector main or cold water return main CWRM. Generally the cold water return main CWRM is arranged in a run parallel to the distribution main CWM and is in fluid communication with the cold water return riser CWR. The cold water return main HWRM collects all the spent cold water collected from the radiant walls  20  for return to the cold water return riser HWR and the cooling system  41 .  
      The thermostatic control for the suite  11  can be fit with a dump valve (not shown) to periodically permit flow therethrough to minimize stagnation in low demand situations or, for simplicity, can operate periodically even during usual demand situations.  
      In testing conducted in Calgary, Alberta, Canada, a system was tested which utilized domestic hot water DHW for both domestic use and heating of student residences using a radiant wall  20 . Heating of adjacent rooms  10   a , 10   b  was simulated using a radiant wall  20  such as that arranged shown in  FIG. 1 . The radiant wall  20  was formed by threading plastic pipe as the thermal tubing  21  through the metal studs in the partition wall  13 , with local thermostatic control of the flow of hot water DHW to each occupant&#39;s room. The testing investigated the adequacy of thermal performance (including comfort and thermal output), durability of building systems (include pipe, drywall, and paint lifetime), and the significance of energy savings. The assessment determined that the system met the above criteria.  
      More specifically test measurements show that a single radiant wall  20 , as tested, had a heating capacity of about 1500 W (4500 Btu/hr), which is sufficient to offset losses from typical residence rooms. It was recognized that end units and top floor units would require additional heating. The heat capacity was determined by calculating the heat transfer from the hot water supply and return temperature differential, the water flow rate, and the heat capacity of the water per unit volume. The industry guide for comfort assessment is ASHRAE&#39;s Standard 55-2004, Thermal Environmental Conditions for Human Occupancy. At Calgary, Alberta&#39;s 99% winter design temperature of −27° C. or 17° F., the proposed system, including window losses, maintained an interior room temperature of 11° C. (52° F.), which compared favorably to the minimum acceptable vertical surface temperature of 10° C. in terms of radiant asymmetry (ASHRAE 2004, p. 7).  
      The wall operating conditions were within conditions deemed acceptable by drywall and paint manufacturers. Prior art piping arrangements that have worn prematurely, having small hot water return water legs, are not used in this system. Further, it was found that it is easy to service radiant wall tubing relative to prior art piping systems such as in-slab radiant piping, because the tubing is enclosed within dry-walled areas.  
      The simulated system was tested with a hot water temperature of 150° F. (10° F. or 5.5° C. higher than the design temperature) and the maximum interior wall temperature temperatures observed was 118° F. (48° C.), which was 4° C. (7° F.) below the warranty limit. Drywall warranties typically allow temperatures up to 125° F. (or 51.5° C.) on a regular basis. Applicant understands that latex paints can be exposed to temperatures of up to 175° F. (80° C.) without degradation.  
      The whole building simulation model was used to estimate annual pump energy use with a conventional dual-piped domestic hot water and building heating system. Pump energy was estimated to be about 5% of total annual energy use. The annual cost saving was estimated to be about 33%, worth about $7,000 CAD at current energy prices. For a building with a local boiler plant, the 60° C. supply water temperature for the system allows a return water temperature suitable to permit condensing boilers to operate in condensing mode and attain efficiencies above 88%.  
      In the testing, the heated wall, at steady-state heat output, had a surface temperature of about 26° C., compared with a known normal range of 18-29° C. (65-85° F.). The supply-return temperature differential was a minimum of about 5.5° C. The flow rate of the water through the wall was 1 USgpm or 0.063 L/s. At a density of 1,000 g/L, this is a mass flow of 63 g/s. With the specific heat of water at 4.2 J/gC, the heat transferred was 245 J/s per ° C. or 245 W/° C. For a 6° C. temperature differential (the approximate difference at maximum heating), the heat transfer was then 1470 W (5000 Btu/hr). The heat loss was calculated for the double room, as its wall area is greater. The heat loss was estimated at about 1320 W at the design outdoor temperature with a temperature differential inside to outside of −49° C. The heat loss comprised 140W from a spandrel area of 2.4 m 2 , 709 W from 5.4 m 2  of windows, 237W from  8 . 1  m 2  of exterior wall, and lastly an estimated loss from infiltration of 233W.  
      The wall heat supply was therefore greater than the wall heat loss. The calculation neglected heat gains from occupants (about 70W per person) and any heat-generating equipment, which would provide an additional “cushion” against heat loss. A window thermal gradient calculation showed that the interior temperature at the −27° C. design temperature is 11° C.  
      While a preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. Consequently, within the scope of the appended claims, it is to be understood that the invention can be practiced otherwise than as specifically described herein.