1、C H-06- 1 Symposium on How Long Can You Go? bow-Energy Buildings through Integrated Design CH-06- 1 - 1 Combining Radiant and Convective Systems with Thermal Mass for a More Comfortable Home (RP-1140) David Scheatzle 253 CH-06- 1-2 Small House with Construction Cost of $100K, Total Energy Cost of $0
2、.88 a Day Jeffrey E. Christian, Paige Pate, Phil Childs, and Jerry Atchley 269 CH-06- 1-3 Assessing the Performance of a Naturally Ventilated Office Building Christine E. Walker, Leslie K. Norford, and Leon R. Glicksman 281 CH-06- 1-4 Energy Performance Evaluation of a Low-Energy Academic Building S
3、hanti D. Pless, Paul A. Torcellini, and John E. Petersen 295 CH-06- 1-5 Low-Energy Building Case Study: IAMU Office and Training Headquarters Tom McDougall, Kevin Nordmeyer, and Curtis J. Klaassen 3 12 CH-06-1 -6 Evaluation of the Low-Energy Design Process and Energy Performance of the Zion National
4、 Park Visitor Center Nicholas L. Long, Paul A. Torcellini, Shanti D. Pless, and Ron Judkoff . 321 CH-06-1-1 (RP-1140) Combining Radiant and Convective Systems with Thermal Mass for a More Comfortable Home David Scheatzle, ArchD, PE, FAIA Life Member ASHRAE ABSTRACT A residential radiant heating and
5、cooling system has been operating and monitored in the Phoenix, Arizona, area for four years (2000-2004). It has demonstrated that controlling surface temperatures of both high and low mass envelope components can provide stable comfort conditions at a lower cost with less noise and higher air quali
6、ty than a conventional air-handling system. The environmental system includes high mass walls, insulated on the exterior, and radiant panels in both the ceiling and the floor mass supplied by a hydronic source (ground-source heat pump). Low mass ceiling panels are used primarily for summer cooling,
7、and the high mass floor panel system is used for both summer cooling and winter heating. The control strategy uses envelope thermal mass to keep the operative temperature of the space within the comfort envelope, using mostly off-peak electrical energy, with less than one hour of on-peak compressor
8、time per day. A system that uses radiant suface control in combination with thermal storage of the buildings mass and a separate system for dehumidijkation and ventilation would appear to be the ultimate method for providing thermal comfort. It would provide indoor conditions, on a year-round basis,
9、 that one experiences on that .perfect” spring or fall day when the climates diurnal cycle is in harmony with the buildings envelope and creating surface/ air temperatures that are ideal for human comfort. Extensive details and performance data with animations can be found at http:/support. caed. as
10、u. eddradiant. INTRODUCTION Objective This was a demonstration project to provide documented performance of a system that combines both radiant and convective systems in a high mass home. During the process of the demonstration, the control system operation was to be refined, the system operating gu
11、idelines established, and the system performance evaluated. History The project began in 1994 when an individual, interested in incorporating radiant technology in the house that he was about to build for himself, requested assistance. The principal investigator agreed to advise on the system design
12、 and assist in obtaining system components ifperformance data would be made available for research purposes (Scheatzle 1996,2003). Construction began in mid-1 995, progressed slowly but steadily, and in January 1999, when the house was almost complete, the ownerhilder sold the house to the second oc
13、cu- pant. A lightening strike in July 1999 damaged both the control system and the data collection system. It was not immediately obvious that data being collected were unreliable and it took a year to resolve all ofthe problems. On August 12, 2000, reliable and calibrated data began to be recorded.
14、 Data for a continuous 40-month period (August 12,2000, through December 2003) are available and describe both the passive and active performance of the house. The house was sold to the current and third owner in February 2005. The original dehumidification system is being upgraded as described late
15、r. David Scheatzle is professor emeritus at Arizona State University, Tempe, Ariz. 02006 ASHRAE. 253 PROJECT DESCRIPTION House Envelope The house is a 2500 fi2 (244 m2) single-story adobe house containing three bedrooms and two baths (Figure 1). The exte- rior adobe walls are insulated on the outsid
16、e with 2 in. (5 cm) of sprayed-on foam. The entire occupied floor area has hydronic tubes buried in the concrete slab. The ceiling contains hydronic capillary tubes just above the plastered surface. The foundation stem wall is insulated on the inside (between the wall and the slab) with 2 in. (5 cm)
17、 foam-board. The 5 in. (1 3 cm) slab, poured over gravel with no insulation below, is an excellent thermal storage device. On top of that is another 2 in. (5 cm) of mass-1 in. (2.5 cm) of grout topped with 1 in. of flagstone. The slab contains 318 in. (1 O mm) diam- eter rubber tubing at a spacing o
18、f 9 in. (23 cm). The exterior walls are constructed of 14 in. (36 cm) adobe. These walls, enclosed in insulation, represent considerable thermal storage. Their exterior length is approximately 300 ft (9 1 m); their height averages 8 ft (2.4 m). There is 95 lineal feet (1 1.4 m) of interior adobe wal
19、l. Still to be answered by simu- lation work is how much of the mass will be usable for thermal storage. For a predominately cooling climate, theory predicts that a cool ceiling would provide better room convection patterns in the summer season, while radiant floors would provide the patterns best f
20、or the heating season. Fifty-two percent of the ceiling area of the home is a radiant panel, sized for a cooling load of approximately 20 Btu/ft2 (60 W/m2). The manufac- turer states that the capillary mats can provide cooling at 27 Btu/ft2 (80 W/m2). To prevent condensation problems, the constructi
21、on details of the roof/ceiling assembly were specially designed (Figure 2). Below the wood roof rafters is a continuous vapor barrier to prevent moisture from reaching a surface whose temperature is below the dew point; then there is 1 in. (2.54 cm) of rigid foam insulation board, 1/2 in. of gypsum
22、board, and 3/8 in. (1 cm) of sand plaster. At a depth of 0.25 in. (6 mm) in from the surface of the plaster is a capil- lary tube mat. The tubes are 0.08 in. (2 mm) diameter plastic spaced at 0.5 in. (12 mm). They are connected by a 0.63 in. (16 mm) supply header and another 0.63 in. (16 mm) return
23、header. Figure 3 is a reflected floor plan showing the ceiling panel layout. Thirteen hundred square feet (1 19 m2) of panels Figure 1 Exterior view of the Carefree house. THERMOCOUPLES THROUGH SECTION CAPILLARY TUBE METAL ROOF 1/16“ ROOF FELT 30 LB PLYWOOD 1/2“ RADIANT BARRIER BATT INSULATION 5“ VA
24、POR BARRIER FOAM 1“ DRY WALL 1/2“ Typical Roof Section -PLASTER 3/8“ . . - . - - . . ti Lore,WSpaiss 7 Baniniuhnon TOP 8 kn insulanon BOIIO 9 Dry Woll lop 11 Cenlng Sudoce 10 Radknl P.ml Surtoc* Figure 2 Section view of roojkeiling assembly thermocouples at changes of materials. 254 ASHRAE Transacti
25、ons: Symposia Figure 4 Vew of Capillary tubes before the application oj plaster: were installed over a floor plan of 2500 ft2 (229 m2). Figure 4 shows capillary tube ceiling mats fastened to gypsum board. Capillary tube ceiling mats are 1 m (3.2 ft) in width and of varying lengths-from 1 m (3.2 ft)
26、to 4.5 m (14.4 ft)-in length. Therefore, a single capillary tube length (from supply header to return header) varies from 2 m (6.4 ft) to 9 m (28.8 ft). Naturally, the temperature drop through a longer tube is greater. So for the cooling mode, the longer the tube, the higher the average temperature.
27、 Since a room can contain mats of several lengths, varying temperatures will occur across a rooms ceiling, although only one ceiling surface sensor was installed in each zone. There are four 3 x 3 ft (91 x 91 cm) operable skylights on the north slope of the roof. Mini-blinds were installed in the sk
28、ylights in April 2002. This has improved the thermal perfor- mance of the house. At certain times of the year prior to the installation of the mini-blinds, direct sun would come through the skylight and strike the center zone sensor, causing spikes in the air temperature and operative temperature. T
29、he skylights provided benefits in the swing seasons when they were opened for venting and night ventilation to extend the passive comfort performance of the house. Windows are double-pane, and with the 4 ft (1.2 m) over- hang around the house, are shaded for most hours of the year. Environmental Con
30、trol System The environmental control system is .made up of both passive and active components. Passive components include the thermal mass of the floor and the heavy mass outside insulated walls, operable skylights, wide overhangs, and low-e coated double-pane operable windows. The active environme
31、ntal control system consists of the radiant floor and ceiling panels supplied by warm and chilled water from a ground-source heat pump cooled by an evapora- tive fluid cooler and heated by flow to vertical wells, the central and zone control system, and a separate convective system-ventilation and d
32、ehumidification package units for indoor air quality. Figure 5 shows a schematic of the entire active environmental control system, a hybrid (radiant convective) system. The radiant system provides both sensible heating and cooling. The nominal 3 ton heat pump produces chilled and hot water for the
33、hydronic radiant system. It receives and rejects heat frodto the ground with a well field of 1 O wells averaging 60 fi (18.7 m) in depth. It also provides domestic hot water. Each zone has a manifold for both the floor and the ceiling. A separate solenoid valve controls the flow to each. The ground
34、loop (wells, etc.) is made of 1-in. plastic tubing. It is divided into three sections in parallel; two of the sections have three wells in series and one section has four wells in series. Oper- ational performance during the summer of 2000 showed that the ground loop heat rejection capacity was insu
35、fficient. This resulted in very high condensing temperatures and lower than expected cooling capacity to the house. So, on May 22,2001, an evaporative closed-loop fluid cooler was installed in series with the ground loop, ASHRAE Transactions: Symposia 255 o 0 WINDSPD c_wvs OGDFRM KFRM.T GD- O C-RET-
36、T -GALS GD-TO R-T CAREFREE. ARIZONA RESIDENCE System Schemotic Showing Sensor Locotions VOI nao Figure 5 System schematics-section with sensor locations. There is an energy recovery ventilator for both the west and the center zones, but not for the east zone. Exhaust air is taken from the kitchen, b
37、aths, and laundry room, and incoming outdoor air goes to the occupied spaces. If indoor humidity is high, indoor air is cycled through the dehumidifiers. The two original dehumidifiers installed by. the builder are now being replaced. The originals were a “basement“ dehumidifier type with a 50 pint
38、(2 L/h) per 24 hour capacity (2000 (Btu/h)/585 W latent). Since they were a self-contained refrigeration cycle, they put heat into the space. Replacements will be two split-system refrigeration units with 1.5 ton (5269 W) air handlers. Their latent removal capacity is 7,400 Bu/h (2166 W) each at 67F
39、 EWB (19.4“C), fan-oper- ated on low (tap setting) speed. A load calculation was done before construction and showed the need for a latent capacity of 12,000 Btuh (35 13 W). The new units will be operated with the existing humidity sensors (one for each unit). At this writ- ing, the intent is to use
40、 55% RH as the upper limit, with a 5% throttling range. A 62F dew-point upper limit is called for in ASHRAE Standard 55; however, the capacity of this control system wont allow for additional dew-point calculations. Heating and Cooling Capacity of Radiant Panels Considering the bare floor and a 3 ft
41、 (7.6 cm) over-pour with tubes at 9 ft (22.9 cm) on center, the estimated heating capacity is 27 Btu/h.ft2 (79 W/m2) (Kilkis and Coley 1995). The ceiling was designed for a cooling capacity of 20 Btu/h.ft2 (60 W/m2) (Kilkis 1995). The maximum cooling capacity (Olesen 1977) of the floor, based on a m
42、aximum room air temperature of 78.8“F (26C) and a minimum floor tempera- ture of 68F (20“C), is 13.3 Btu/h.ft2 (42 W/m2). Installed Sensors Figure 6 shows the house floor plan with the location of installed sensors. These include sensors for surface tempera- tures, air temperatures, and relative hum
43、idity. Also shown on the plan are the locations of thermocouples that provide data to the data collection system. Figure 5 shows the system sche- matic with the location of sensors that indicate the perfor- mance of the ground-source heat pump and the hydronic distribution system. An electrical mete
44、r with a pulse output is installed on the heat pump (includes the ground pump), while a second meter monitors the total house consumption. Weather Data A separate weather file was developed for simulation work. Weather data were compiled from the data collected at the site project (elevation 2500 fi
45、) and also the Phoenix TMY2 file. DEVELOPMENT OF CONTROL PROGRAM Variations in Building Load The project house is well insulated, well shaded, and has very low infiltration. Most load changes are gradual and cycli- cal with the diurnal cycle. Even though the roof/ceiling assem- bly is well insulated
46、, the ceiling surface presents the largest liability both in summer and in winter. Its temperature can rise to 83.4“F (28C) in a summer afternoon and drop to 64.4“F (18C) at sunrise on a winter morning. As for the internal loads, the house was occupied by an individual (and a large dog) whose daily
47、routine resulted in consistently minimal consumption; so, the internal loads were very predictable. Pre- construction load calculations showed a need for a cooling capacity of 19-22 Btu/h+12 (60-70 W/m2), but actual perfor- mance data may show a lower requirement. The Control System In general, the
48、best practice is to apply radiant heating from a floor panel. A warm floor provides two forms of heat transfer, radiation and convection. Heat rises by convection, thus providing a relatively even temperature distribution in the vertical plane. For a cool ceiling panel, similar effects are true. It
49、absorbs heat by radiation and provides a portion of its heat transfer by convection. There is a saying in the comfort busi- ness: “Cold head, warm feet.“ The head, being the warmest exposed surface of the body; benefits from a cool ceiling when trying to lose heat. 256 ASHRAE Transactions: Symposia Figure 6 Floor plan showing sensor locutions. Both the floor and ceiling panels can be provided with either warm or cold water. There are three zones that will allow flow through either the floor panel only, the ceiling panel only, or both the floor and the ceiling panels
