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Reference Publication:   W. Mark McGinley, Professor, Department of Civil, Architectural, Agricultural and Biosystems Engineering, North Carolina A & T State University, Greensboro NC 27411 USA , Alaina Jones, Graduate Student, Department of Civil, Architectural, Agricultural and Biosystems Engineering, North Carolina A & T State University, Greensboro NC 27411 USA, Carolyn Turner, Associate Dean, School of Agriculture, North Carolina A & T State University, Greensboro NC 27411 USA, and Subrato Chandra, David Beal, Danny Parker, Neil Moyer, Janet Mclvaine , Florida Solar Energy Center, 1679 Clearlake Rd, Cocoa, FL 32922. Optimizing Manufactured Housing Energy Use. Symposium on Improving Building Systems in Hot and Humid Climates, Richardson, Texas, May 17-19, 2004.
 
Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof.
Optimizing Manufactured Housing Energy Use
Florida Solar Energy Center (FSEC), North Carolina A & T State University

Abstract

In partnership with the Florida Solar Energy Center (FSEC), two manufactured homes were located on North Carolina A&T State University’s campus in Greensboro, NC and used in a side-by-side energy consumption comparison. One of the homes was built to the basic HUD code standard and the other was constructed with features expected to produce a home that was 50% more energy efficient.

FSEC and NCATSU began monitoring energy performance in both homes. In addition, the performance of each unit was evaluated using a DOE2 based computer energy analysis program developed by FSEC. A comparison of the performance of the units shows a measured energy savings in the more energy efficient unit of 52% for the Heating, cooling, and DHW energy use. This compares well with the energy savings predicted by the FSEC Energy Gauge program of 57%, even when accounting for the warmer than usual winter experienced during the testing period.

1.0 INTRODUCTION

As part of a project funded by the North Carolina Department of Administration - Energy Division, and as Part of the US Dept of Energy’s Building America Program, researchers in the Center for Energy Research and Technology (CERT) at North Carolina A & T State University evaluated technologies to improve the energy efficiency of manufactured housing.

The partnership effort described by this report required CERT researchers to monitor the energy use of two side-by-side manufactured housing units on the campus of North Carolina A & T State University in cooperation with the Florida Solar Energy Center (FSEC). One of the units monitored was designed and built to basic HUD code requirements [HUD, 1999] and the other was designed to use at least 50% less energy (Building America compliant).

As part of this study, both units were also analyzed using the FSEC developed ENERGY GAUGE software program. This program predicts building energy consumption using the DOE 2 analysis engine with a user friendly front end that develops DOE2 input files and models that are more appropriate for residential building systems.

In addition, in this second year, modifications were made to the solar hot water heating system in the energy efficient housing unit to help improve the performance of this system. Further, a number of the incandescent light bulbs in the energy unit were replaced with compact fluorescent bulbs. These changes were staged to allow an evaluation of the effect each of these measures had on the energy use in the homes.

The following report summarizes the results of the second year of the effort described above (the first years results were previously reported) [McGinley, 2002].

2.0 Standard (HUD CODE) and Energy (ENERGY EFFICIENT) Manufactured Home Description

Each of the two manufactured homes used in this study have 1,528 ft 2 of living area, 3 bedrooms and 2 baths. Each of the two housing units had identical floor plans. The homes were oriented on the site with the front facing east. Both houses were furnished. Exterior finishes were of medium color, with dark roofs. See Figures 1 through 3.

Each home unoccupied; however incandescent lights on timers were used to simulate occupancy loading. One of the homes was constructed using conventional HUD code provisions and the other was designed to be 50% more energy efficient. Construction differences between the two homes are listed in Table 1.

The Standard housing unit used a perimeter ducting system, while the Energy housing unit used a central trunk line. The higher thermal resistance of the energy home building envelope allows this more efficient central distribution system and a reduction in compressor tonnage, which reduces initial costs and duct losses. See Figures 1 and 2.

It should be noted that the Energy housing unit incorporated the use of a solar hot water heater, with a 66-gallon hot water tank, while the “Standard” home used an electric hot water heater with a 40-gallon tank.

Table 1 Summary of Construction of the Two Homes

NCATSU Side-by-Side Study of HUD Code Homes
Specifications of Standard and Energy Construction
Characteristic

Standard Home

Energy Home

Floor Insulation

R-11

R-22

Wall Insulation

R-11

R-13

Ceiling Insulation

R-20

R-33 roof deck radiant barrier

Windows

Single Pane with Interior Storm Windows

Low-E Thermopane Windows

Exterior Doors

Storm Door on Front door only

Storm Door on All doors

Marriage Wall Seal

Fiberglass Pad

SOF-Seal Gasket

Heating System

Electric Resistance Furnace

Heat Pump HSPF7.5

Cooling System

Central Air Conditioning SEER10 - 3 ton

Central Heat Pump SEER12 - 2.0 ton

Water Heater

Electric Water Heater 40 gallon capacity

Solar Water Heater – 66 gallon capacity

Duct Joints

Industry Standard

Sealed with Mastic

Duct System

Perimeter Duct System

Main Trunk Line

House Leakage

ACH50 = 10

ACH50 = 9

*(Note that the Energy House values for Duct Leakage and House leakage were based on retests done after August 2001 repairs)


Figure 1. Floor Plan and HVAC layout for the Base HUD Code (Standard) Housing Unit (Courtesy of Palm Harbor Homes)


Figure 2. Floor Plan and HVAC Layout for the Energy Efficient (ENERGY) Housing Unit (Courtesy of Palm Harbor Homes)

3.0 Monitoring Program

A computerized data logging system was used in each house to monitor:

  1. The interior temperature and relative humidity.
  2. The power consumption of the whole house.
  3. The power consumption of the air conditioning/heat pump compressor.
  4. The power consumption of the air handler fan.
  5. The power consumption of the electric resistance heat (primary heating in the standard house, secondary heating for the energy house).
  6. The power consumption of water heater and electric water tank coil.
  7. The exterior temperature and relative humidity, solar radiation (both parallel and at the solar panel angle), and wind speed.

The data-loggers were connected to FSEC’s mainframe computer via modem, and downloaded automatically. Data were sampled at 6 second intervals and recorded in hourly intervals.

All appliances in the home were unplugged except for the hot water heater, HVAC system and some incandescent lights. There were also a few miscellaneous devices such as the data logger, phones, and controls that show as a minor electrical load. The incandescent lights were used to simulate an occupancy load of 1.5 persons and were run on the following schedule; 500 watts of lights were on 24 hours a day 7 days a week, 500 watts of lights are switched on by timers from 4 pm to 12 pm, 200 watts of lights are switched on by timers from 6 am to 9 am.

In addition, on weekdays, there were two hot water draws of 40 gallons each, one in the morning and one in the late afternoon for each of the houses. This water draw was used to simulate an average weekly water use of a typical residence.

A comparison of the performance of the units over the period from January 2001 to March 2002 was made and reported in the first year report. This report summarized the initial poor performance of the Energy housing unit that resulted from an excessively high air-handler fan speed that significantly reduced the efficiency of the system, a very large duct leak resulting from an improperly set Y-connection coming off the main supply duct trunk line, a supply duct collar failure and a poorly sealed opening around the refrigerant line and drain between the return and supply side of the coil plenum creating a return air bypass around the coil. These items were repaired by September 2001 and “good” data were obtained from September 1, 2001 to August 16, 2002.

Both homes were on cooling only mode from September 1, 2001 through October 26, 2001 at 7:00 pm. After this time, both homes were on heating only mode until, April 16, 2002 at 2:40 pm, where they were switched over to cooling only mode again until October, 2002. It should be noted that one of the critical findings of the first year of the investigation indicated that current manufactured home set up procedures may not be adequate to ensure predicted performance of the energy efficient home units. As a result, Palm Harbor, one of the industry partners in this investigation, has instituted steps to improve installation/setup procedures.

It was also found that the standby losses in the solar hot water heater in the Energy Unit were significant and on long idle periods were sufficient to make the overall efficiency of the solar hot water heater less than the standard electric unit. To help alleviate these stand-by losses, the solar water tank piping insulation was upgraded on March 6, 2002 and its effect on the water system performance was evaluated. The solar hot water tank had a significant amount of copper and plastic tubing exposed in the original installation configuration. Additional pipe insulation was applied to all accessible pipe surfaces and the effects of this upgrade was evaluated.

On May 1, 2002, in an effort to further improve the performance of the solar hot water heater, the solar hot water tank in the energy unit was wrapped with a R5 foil bubble wrap insulating blanket over the sides and most of the top of the tank. Figure 3 shows the tank with the foil insulation and additional pipe insulation applied.

The final modification made to the Energy Housing unit was made on June 4, 2002. At this time, three of the light fixtures that were on evening 4 hour timed duration were changed from 100 watt incandescent lamps to 25 watt compact fluorescent lamps.


Figure 3. The Solar Hot Water Tank with R5 Insulating Blanket and additional Pipe Insulation Located in the Energy Efficient Manufactured Housing Unit

4.0 Results and Discussion

4.1 Energy Use Results and Discussion

The measured total energy used by each of the housing units for cooling and heating are shown in tables below. Table 2 shows the energy used for heating and cooling the Standard Housing Unit over the period of January through August in 2002. The Standard Unit data logger was struck by lighting in mid August, 2002 and all data after this point was not included since only partial data is available and comparisons of performance were not possible. Table 3 shows a similar summary of the cooling and heating energy used by the Energy Housing Unit.

Tables 4 and 5 show the energy used for domestic hot water production for the Standard and Energy units, respectively for these same periods.

Table 2. Standard Housing Unit Heating and Cooling Energy Use

 

 

C & H ENERGY Measured Values (kWh)

SEPT.

OCT.

NOV.

DEC.

JAN.

FEB.

MAR.

APRIL

MAY

JUNE

JULY

AUG.

2001 values

492

448

649

1741

2495

850

629

384

566

991

853

1066

2002 values

 

 

 

 

2120

1717

1228

502

438

939

1079

511


Table 3. Energy Housing Unit Heating and Cooling Energy Use

 

 

C & H ENERGY Measured Values (kWh)

SEPT.

OCT.

NOV.

DEC.

JAN.

FEB.

MAR.

APRIL

MAY

JUNE

JULY

AUG.

2001 values

337

206

151

453

1087

473

427

185

528

891

851

672

2002 values

 

 

 

 

681

537

378

242

312

603

668

627


Table 4. Standard Housing Unit Energy Use for Domestic Hot Water Production

 

 

DHW Measured Values (kWh)

SEPT.

OCT.

NOV.

DEC.

JAN.

FEB.

MAR.

APRIL

MAY

JUNE

JULY

AUG.

2001 values

198

268

250

213

0

0

218

245

258

227

208

214

2002 values

 

 

 

 

295

281

283

265

280

192

200

85.2


Table 5. Energy Housing Unit Energy Use for Domestic Hot Water Production

 

 

DHW Measured Values (kWh)

SEPT.

OCT.

NOV.

DEC.

JAN.

FEB.

MAR.

APRIL

MAY

JUNE

JULY

AUG.

2001 values

133

176

204

190

0

0

246

184

183

141

152

127

2002 values

 

 

 

 

251

212

203

146

157

74.8

80.3

83

Also listed in each table are the monthly energy use measured during the first phase of this investigation, January through August (2001). Note that the Energy Housing Unit data prior to August 2001 is suspect due to problems in the ducting and HVAC system, as discussed previously.

Only the cooling and heating energy, and energy used for domestic hot water production, will be discussed in this and subsequent sections since each housing unit was not occupied and was assumed to use essentially the same amount of energy for the occupancy simulation. When the three incandescent bulbs replaced with compact fluoresce bulbs in the energy unit, the reduction in energy use for lighting load was not of concern, what was being evaluated was the impact this change had on the cooling load in the housing unit.

The total cooling energy used by the Standard house from April 2002 to August 16 th 2002 was 3468 kW-hrs. The total cooling energy used by the Energy house from April 2002 to August 31 st, 2002, was 2451 kW-hrs. If it can be assumed that about 500 kW-hr would be used for the reminder of the August month in the Standard housing unit (~1/2 the 2001 values and about 2 times the 2002 value), then the Energy housing unit used approximately (1- 2451/(3468+500) x 100), or a 38.2 % less energy than the Standard unit for cooling during this time. The totals for the same period in 2001 were 3860 kW-hr (Standard) and 3127 kW-hr (Energy), a 19 % difference. You can see that there is an increased difference in energy efficiency of the two housing units in the second year of monitoring during the cooling season. This may be at least partially due to less waste heat being dumped into the energy unit by the solar hot water heater and compact fluorescent lights. This will be discussed later.

Over the first and second phase of this investigation there was only one complete heating season observed. The total heating energy used by the Standard house from November 2001 to March 2002 was 7454 kW-hrs. The total heating energy used by the Energy house over the same time period was 2199 kW-hr. Over this time, the Energy housing unit used approximately 70 % less heating energy than the Standard unit.

The total heating and cooling energy used by the Standard housing unit from September, 2001 through August, 2002 was 12,365 kW-hr (a sequential heating and cooling season). Over the same period of time, the Energy housing unit used 5194 kW-hr, a 58% reduction.

The total energy used for domestic hot water production from September 1, 2001 to August 16 th, 2002 in the Standard unit was 2810 kW-hr. The total energy used for domestic hot water production from September 1, 2001 to August 31, 2002 in the Energy (Solar) unit used 1911 kW-hr of energy. If it is assumed that the Standard unit hot water tank would used about 110 kW-hr for the rest of the August month (about ½ of that used in previous months), the Solar hot water tank in the Energy unit used approximately 34% less energy than the Standard unit.

Combining the energy used for domestic hot water production with that used for heating and cooling produced a total of 15,285 kW-hr of energy used by the Standard housing unit between September 1, 2001 and August 31 st, 2002. The Energy housing unit used a total of 7,105 kW-hr over the same period of time. The Energy unit used 53 % less energy than the Standard unit for heating cooling and production of domestic hot water over this period. As will be discussed in the next section, the improvements made on the solar hot water tank and their effects on energy use suggests that the Energy housing unit would use even less energy than the Standard housing unit with these changes in effect over a entire year.

4.2 Effect of Changes in the Solar Hot Tank and the Compact Fluorescent Fixtures

The pipe insulation on the solar hot water tank was upgraded on March 6, 2002. This increase in insulation on the hot water piping appears to have had a significant effect on the performance of the solar hot water system and appears to have reduced the stand-by heat losses in the system.

Since no hot water draws are made on the weekends, it is possible to examine how standby losses are influenced by system changes by looking at this time period specifically. The stand by losses for 18 week end days in the period of March 6 though April 30, 2002 showed that the pipe wrap has cut standby energy losses for the energy house by about 65% (an average of 2.43 kWh/ day (2001) vs. 0.85 kWh/day (2002)) over a similar period last year.

In addition, the reduction of standby losses helped the solar hot water system use less energy than the conventional electric system in the month of March. The Standard Unit used 283 kW-hr and the solar hot water system used 203 kW-hr, a 28.2% reduction. This reduction was further increased in the month of April where the standard system used 265 kW-hr and the Solar system used 146 kW-hr, a 45% reduction. It should be noted that these values represent significant reductions in energy use when they are compared to 2001 values where the solar system actually used more energy than the standard unit in March 2001 and used only 25% less than the standard unit in April 2001.

In an effort to further improve the performance of the solar hot water heater, the water tank was wrapped with a foil bubble wrap insulating blanket over the sides and most of the top of the tank.

Over the month of May, the total energy used for DWH heating was 137.8 kWh for the Energy housing unit and 249.6 kWh for the Standard housing unit. This represents a 45% reduction in energy use for the solar hot water system, about the same as the 45% reduction shown for the month of April.

A comparison of the tank losses over the weekends in months of April, 2002 and May, 2002 give a good indication of actual losses since there are no tank draws on these days. This data shows an average daily week end loss of 2.83 kWh for the Standard home and a 3.08 kWh for the Energy home for the Month of April and an average daily week end loss of 3.92 kWh for the Standard home and a 2.97 kWh for the Energy home for the month of May. There appears to be a little improvement in tank heat loss over the two periods.

The total energy used over the month of June, 2002 for DWH heating was 74.8 kWh for the Energy House and 192.2 kWh for the Standard home. This represents a 63% reduction in energy use with the solar hot water system (compared to the 45% difference for May). This appears to indicate the tank insulation may be having an effect on the losses in the tank. It should be noted that the solar radiation was about the same as the month of May (within 3%) but the water consumption was slightly less. These results suggest that the tank wrap may be reducing some of the heat losses.

The total energy used over the month of July, 2002 for DWH heating was 80.3 kWh for the Energy House and 200.25 kWh for the Standard home. This represents a 60% reduction in energy use with the solar hot water system. This compares well with the June reduction of 63% with about 11% less solar radiation in the month of July. This reduction and those in May and June are significantly greater than the efficiencies observed in 2001 without tank and piping insulation where energy use reductions ranged from 27% to 40%.

The total energy used over the period of August 1, 2002 through August 15, 2002 for DWH heating was 27.13 kWh for the Energy House and 85.18 kWh for the Standard home. This represents a 68% reduction in energy use with the solar hot water system. This compares well with the June and July reductions of 63 and 60%, respectively. These results appear to indicate the tank and pipe insulation is reducing the losses in the tank, particularly the standby losses and improving the efficiency of the solar hot water system.

To look at the impact of improved insulation of the solar hot water system on the cooling energy used in the Energy housing unit, the total cooling energy used for the months of March through August must be examined. To remove the effects of the outside temperature on this evaluation, a comparison of the percentage difference between the cooling energy used by the Standard home and the Energy home will be made. This comparison shows that in the months of March 2002 to August 2002 the Energy housing unit used 29% to 69% less cooling energy than the Standard housing unit. In the same period in 2001, this reduction ranged from only 3% to 48%. This suggests that the improvements in tank insulation may also have had a significant effect on the cooling load within the Energy home. However, the previously described deficiencies in the Energy Unit present in early 2001 make definite conclusions relative to this effect difficult.

In the Energy housing unit, three of the 100 watt incandescent lamps that were on the evening 4 hour timed duration were exchanged for 25 watt compact fluorescent lamps on June 4 th, 2002. This change did appear to have a small effect on the cooling load in the Energy housing unit. The relative cooling energy used by each of the housing units from June, 2002 through August 2002 showed a small change. The percentage reduction in cooling energy used by the Energy housing unit increased from about 30% to 38 percent. However, it is difficult to isolate the effects of the improvements in the solar hot water system insulation and the effects of the compact fluorescent bulbs. In any event, these effects appear to be much smaller than that produced by the hot water system changes.

4.3 Energy Analysis

The two housing units described in the previous sections were analyzed using a computer simulation program. The Energy Gauge Program (Version 1.25) developed by the Florida Solar Energy Center was used for the analysis. The Energy Gauge Program uses the basic DOE 2 energy analysis engine to provide an hourly energy use simulation for light commercial and residential structures [Danny Parker, et-al, 1999]. This program was developed to provide a simple to use interface for the DOE2 analysis program that more accurately analyzes the energy use of single and multifamily residences, and light commercial structures.

An analytical model was developed for each of the manufactured home units. These models were essentially the same with differences only in the R-values in the various building envelope components, the duct leakage values, the heating and cooling equipment and the fenestration properties. Figure 4 shows the wire model of the building envelope configuration used for the Standard Home. The Energy Unit model was similar.

The envelope leakage values were measured and these values were used in the analysis (See Table1). Table 1, and Figure 4 also show the window and door U values as well as the HVAC system properties for the unit. In addition, a uniform three-foot crawl space was assumed in the analysis of both houses. The Input Summary Sheets for each of the Energy Gauge runs are shown in Figures 4 and 5. It should be noted that the solar hot water heater was not incorporated in the analysis, a standard electrical unit was assumed in both unit’s analyses.

The analysis of each of the manufactured housing units was also repeated using the newest version of the Energy Gauge program, Version 2.0. This program was reported to have made changes in the analysis modeling and incorporated a number of “bug fixes”. The same input files were used for both set of analyses, Version 1.25 and Version 2.0.


Figure 4. Standard Unit Analysis Model Configuration

Figure 4a. Standard Housing Unit ENERGY Gauge Input Summary
Figure 4b. Standard Housing Unit ENERGY Gauge Input Summary
Figure 4c. Standard Housing Unit ENERGY Gauge Input Summary
Figure 5a. Energy Housing Unit ENERGY Gauge Input Summary

Figure 5b. Energy Housing Unit ENERGY Gauge Input Summary
Figure 5c. Energy Housing Unit ENERGY Gauge Input Summary

Table 6 shows the predicted monthly heating and cooling energy use of the Standard housing unit for September through August (Obtained from both versions of the Energy Gauge program). Also shown in the table is the measured monthly energy use, as well as the percentage difference between the measured and predicted values.

Examination of Table 6, shows that the predicted values ranged from 13 % under the actual usage to 265 % over the actual usage of energy. The analysis model appears to generally underestimate the energy use in the full cooling months and over estimate the energy use in the heating months. Examination of Table 6 also shows that Version 2 of the Energy Gauge program predicts a greater energy use for the Standard housing unit, than Version 1.25. Although there is not good agreement between any of the energy use predictions and the measured values, it appears that the latest version of the program provides a slightly better prediction. The reason for the discrepancy between predicted and measured values relates to the actual weather conditions experienced by the housing units and will be discussed later.

Table 7 shows the predicted heating and cooling energy use for the Energy housing unit for September through August (Obtained from both versions of the Energy Gauge program). Also shown in the table is the measured monthly energy use, for both years as well as the percentage difference between the measured and predicted values.

Table 6. Standard Housing Unit Analysis for Heating and Cooling Energy Use Predicted and Measured

Table 7. Energy Housing Unit Analysis for Heating and Cooling Energy Use Predicted and Measured

As can be seen by examining Table 7, the predicted values ranged from 2 % under the actual usage to 245% over the actual usage of energy. Even though there were problems with the ducting and HVAC system in the Energy housing unit in early 2001, both analyses appear to generally underestimate the energy use during the cooling (even partially cooling) months, and significantly over estimate the energy use during the heating months for the Energy home.

The results of these analyses also show that Version 2 of the Energy Gauge program predicts a greater energy use for the Energy housing unit, than Version 1.25. Again, there is not good agreement between both programs energy use predictions and the measured values.

If we look at the two sets of analyses we can see a similar trend in the difference between the predicted and measured values. It is likely that a significant amount of this can be attributed to the difference between the actual outside temperatures and those assumed by the analysis program. To evaluate whether this is a significant cause for the inaccuracy of the prediction, a comparison of cooling and heating degree days can be made for both the actual measured outside temperatures and those assumed by the analysis programs.

The average hourly outside temperature measured at the housing units was examined and the heating degree day value (HDD) for each hour was calculated using the following formula:

HDD= (65-T)/24, T=average hourly ambient temperature

These values were added for each 24 hour period, excluding negative values. To calculate the HDD value for the heating months, the HDD values for all the days of that month were added.

A similar procedure was used for calculating the cooling degree day values (CDD), except the following formula was used:

CDD= (T-65)/24, T=average hourly ambient temperature

The predicted HDD and CDD values were also calculated based on the average hourly ambient temperatures listed in energy gauge weather data file.

The results of this analysis are presented in Table 9. Examination of these results indicates that the housing units experienced fewer heating degree days than that assumed by the analysis and experienced greater cooling degree days than assumed by the analysis. This suggests that the analysis will generally over estimate the energy used during the heating season and underestimate the energy used in the cooling season. This pattern is what was observed and suggests that inaccuracies of energy use prediction are, at least in part, weather driven. It should also be noted that the actual home did not use the appliances assumed in the analysis and these will provide some heat loading in the homes not present in the actual homes.

Table 9. Cooling and Heating Degree Day Analysis Results- Both Measured and Assumed

However, if the predicted energy savings is compared to the actual energy savings, a reasonable agreement is achieved. Table 7 shows that the total

cooling and heating energy used by the Standard housing unit for the year defined as September 2001 through August 2002 is 12365 kW-hr (adding 500 kW-hr for energy use after Data logger failure). For the same period of time, the Energy housing unit used 5194 kW-hr (Table 8), a 58% difference. The yearly cooling and heating energy use difference between the Standard and Energy housing units predicted by the Energy gauge program is 63% for Version 2.0 and 66% for Version 1.25. This suggests good agreement between predicted and measured energy savings and is similar to that found by others [Parker et-al, 1998].

In addition, the energy savings prediction for cooling, heating and domestic hot water production is approximately as accurate with a predicted savings of 54% (Version 2.0) to 61% and a measured savings of 53%.

It appears that The ENERGY Gauge program gives a reasonably accurate prediction of energy savings and Version 2.0 appears to be slightly more accurate than Version 1.25.

5.0 Conclusions

Based on the results of the investigation summarized in this report, it can be concluded that

  1. The changes in the building envelopes, HVAC systems (increases in efficiency and reduction in tonnage), HVAC ducts, and fenestrations between the HUD code and Energy efficient manufactured homes located on the campus of North Carolina A & T State University appear to be meeting the goal of a 50% reduction in energy consumption. The yearly measured energy savings for heating and cooling energy is 58%, and 53% for heating, cooling and production of domestic hot water.
  2. Care needs to be exercised in the setup of the manufactured housing units or relatively minor construction deficiencies can significantly reduce energy efficiency of manufactured housing units. Many of these items are unknown to the homeowner and procedures must be developed to ensure this does not happen in the field.
  3. Although the Energy Gauge Energy analysis program did not give an accurate prediction of energy use for typical manufactured housing configurations over the period measured, it did appear to give a reasonably accurate prediction of energy savings. The predicted energy savings for the units evaluated in this investigation ranged from 54% to 63%, while the measure values ranged from 53% to 58%. Version 2.0 of the Energy Gauge Program appeared to provide the more accurate predictions of energy savings.
  4. The increase in pipe insulation and an increase in tank insulation increased not only the energy efficiency of the solar hot water heater by reducing stand-by losses but also reduced the cooling load in the manufactured housing unit, significantly increasing the overall energy efficiency of the unit. It appears exposed piping can significantly affect the energy efficiency of the solar hot water heater.
  5. Replacement of incandescent lamps with compact fluorescent bulbs not only reduced lighting energy use, but also may have slightly reduced the cooling load in manufactured housing units, while providing essentially the same lighting levels.

6.0 References

  1. Code of Federal Regulations Housing and Urban Development [HUD], Manufactured Home Construction and Safety Standards, 24, Part 3280, US Government Printing Office, 1999.
  2. McGinley, W. M., “Study of Innovative Manufactured Housing Envelope Materials”, Final Report to the Florida Solar Energy Center, Under the Building America Industrialized Housing Partnership, April 2002.
  3. Parker, D. et.al., 1999. "Energy Gauge® USA: A Residential Building Energy Simulation Design Tool", Proceedings of Building Simulation ’99. International Building Performance Simulation Association, Organizing Committee for the 6th International IBPSA Conference, Department of Architecture Texas A&M University, TX.

7.0 Acknoweledgements

The authors would like to express their sincere appreciation to George James of the US Department of Energy – Building America Program and Larry Shirley of the North Carolina State Energy Office, Department of Administration for their support of this investigation.

 





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