• Manufactured Housing Energy Use Study, North Carolina A&T

Side-by-side monitoring of two manufactured homes at North Carolina Agricultural and Technical State University (NCA&TSU), evaluated the value of a variety of energy saving technologies and techniques. (Figure 50 and Table 28) Home instrumentation measured energy consumption as well as interior and exterior climatic conditions. The “standard home,” designed and built to basic HUD code requirements, represented the control home. Modified to use at least 50% less energy, the “energy home” met Building America standards. Cooperating researchers at NCA&TSU and FSEC investigated energy feature performance and compared actual energy used to energy modeling program predictions. In-situ energy performance data provided researchers with interesting information on both issues.

Figure 50 Side-by-side monitoring of manufactured homes at NCA&TSU.

Each model contained 1,528 ft 2 of living area with nearly identical floor plans. Though the homes were unoccupied during the testing, home lighting and water heating use was simulated with timers. A datalogger in each home recorded: (1) the interior and exterior temperature and humidity along with solar radiation and wind speed, (2) the home’s total power consumption, (3) the air conditioning/heat pump compressor, air handler fan, and electric resistance heater use (primary heater in the standard house, backup or emergency heater for the energy house), and (4) water heating and water usage data.

The energy house features combined higher insulation values, improved windows, centralized and airtight duct design, high efficiency heat pump, and a solar water heater. Feature-by-feature construction differences are highlighted in Table 28.

Data collection on the two homes began in early January 2001 and continued through this reporting period. Palm Harbor Homes in Siler City manufactured both homes, the results for program year three and four are detailed below.

Year 4 Side-by-Side Monitoring Results

During Phase 2, modifications were made to the solar water heating system in the energy efficient housing unit to help improve the performance 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 of each measure on the home’s energy use.

Based on investigative results, it can be concluded that:

• Changes in the building envelope, HVAC and duct systems, and fenestrations in the energy home met researchers’ 50% energy use reduction goal. Measured annual energy savings for heating and cooling energy was 58%, and 53% for heating, cooling, and hot water production.
• Care should be exercised in the manufactured housing unit setup or relatively minor construction deficiencies can significantly reduce a home’s energy efficiency. Many of these items are invisible to the homeowner; therefore procedures must be developed to ensure that deficiencies do not occur during setup.
• The Energy Gauge energy analysis program appears to give a reasonably accurate prediction for expected energy use reduction in a typical manufactured housing configuration. The predicted energy savings for the housing units evaluated in this investigation ranged from 54% to 63%, while the measured values ranged from 53% to 58%. Version 2.0 of the Energy Gauge Program provided a more accurate energy savings prediction than the older software versions.
• An increase in pipe and tank insulation can increase not only the energy efficiency of a solar water heater by reducing stand-by losses, but also can reduce the cooling load in a manufactured housing unit and increase the overall energy efficiency of the water heating unit. Even small amounts of exposed piping can significantly affect the energy efficiency of the water heating system.
• While providing essentially the same lighting levels, replacing incandescent lamps with compact fluorescent bulbs not only reduces lighting energy use, but also reduces the home cooling load.

The total measured energy used by each of the housing units for cooling and heating are shown in tables below. Table 29 shows the energy used for heating and cooling the standard housing unit from January through August of 2002. The standard home datalogger was struck by lighting in mid-August 2002. Data after this point was not included since only partial data is available and performance comparisons were not possible. Table 30 shows a summary of the cooling and heating energy used by the energy housing unit. Tables 31 and 32 list the energy use for hot water production for the standard and energy units, respectively.

Also listed in each table are the monthly energy use values measured during the first phase of this investigation, January through August 2001. Please note that the energy housing unit data prior to August 2001 is suspect due to duct and HVAC system problems later corrected. The entire data set, including, temperature, relative humidity, solar radiation, and power use is listed on the FSEC web site www.infomonitors.com.

The total energy used for water heating and central cooling over the period of August 1 through August 15 was 363.5 kWh for the energy home and 596 kWh for the standard home. This represents a 40 % reduction in energy use between the two homes.

The total energy used over the period of August 1 through August 15 for water 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 water heating system and compares well with the June and July reductions of 63% and 60%, respectively. Consistent findings indicate that the tank and piping insulation has reduced the standby tank losses and improved the solar water system efficiency.

In the energy housing unit, three of the 100 watt incandescent lamps that were on the evening four-hour timed duration were exchanged for 25 watt compact fluorescent lamps on June 4th. 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%. However, it is difficult to isolate the effects of the improvements in the solar water heating 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.

Year 3 Side-by-Side Monitoring Results:

Figure 51 Heating season consumption and savings for side by side study of Energy Star Manufactured Housing.

Heating system savings (2001 to 2002) were a remarkable 70% during Phase 1. Cooling energy season savings were 36%, less than heating but still very substantial. The combined heating, cooling, and water heating savings were 52% for a 9-month period. (Figure 51)

In addition to the energy monitoring effort, NCA&TSU researchers investigated the feasibility of replacing the conventional framing/envelope used in manufactured/industrial housing with alternative systems. Included in this evaluation, was an analysis of the energy impact of using aerated autoclaved concrete (AAC) flooring systems and structural insulated panels (SIP) to supplant traditional wall and roofing
systems. The economic viability of using AAC blocks for structural skirting /foundation around the model units also was evaluated.

Analysis’ results determined:

The best manufactured home energy performance can be achieved using the SIP wall and roof systems with the AAC plank. This performance can be further enhanced with an R-8 unvented crawl space. Though a manufactured home performs best with these alternative systems, the cost to include them may not make economic sense.

• AAC planks can be designed to replace both the steel frame and flooring systems for HUD code manufactured housing units and modular units. These planks also can be modified to incorporate built-in insulated ducts.
• AAC planks are pre-manufactured and require less assembly labor than a typical stick framed unit, but including the plank flooring would increase framing costs by 28%. The heavier weight of an AAC system might exacerbate high framing costs. Similarly, comparative analysis results found that replacing a conventional framing system with a SIP system would increase framing costs by 66%.
• At the current prices for energy and wood products, neither the AAC plank system nor the SIP systems are as economically effective as improvements in the current conventional HVAC systems, steel and wood framing, sheathing systems, and air barriers with respect to improving energy performance.
• The use of AAC planks has the potential to be economically viable in the modular housing market, especially if used with sealed crawl space foundation systems, where their improved resistance to moisture degradation would be very important.
• SIP wall and roof systems also could prove to be economically viable if the price of wood energy increases, and the SIP manufacturing costs decrease through large volume purchases.
• The proposed AAC planking system presents a system that is significantly less affected by water and moisture degradation and may be effective in reducing manufactured housing units’ susceptibility to flood damage. These systems also are not susceptible to termite attack.
• The savings from reduced transportation damage from greater durability and increased floor system stiffness were not addressed in this investigation. It wouldn’t take many days of damage repair (at about $300/person-day for personnel costs related to transportation) to vastly improve the economics of these alternative systems.
  
  
• Portable Classrooms

Project Overview

This is primarily a WSU (with subcontractors Oregon and Idaho) and Pacific Northwest National Lab (PNNL) task. Other partners include FSEC, UCFIE, the State Energy Offices of Oregon and Idaho, school districts in Portland, Oregon, in Boise, Idaho and Marysville, Washington, regional utilities, manufacturers, and other stakeholders in the Pacific Northwest.

The objective of this task is to promote the adoption of energy efficient portable classrooms in the Pacific Northwest that provide an enhanced learning environment, high indoor air quality, and both substantial and cost-effective energy savings. BAIHP staff focus on four main goals: (1) offering technical assistance to portable classroom manufacturers, school districts, and related organizations, (2) field assessment, monitoring, and analysis of innovative building technologies and energy saving features to determine their value, (3) facilitation of collaborative agreements among regional utilities, northwestern portable classroom manufacturers and materials and equipment suppliers, as well as school districts, and state education departments and their affiliates, and (4) conducting and creating educational opportunities to advance the widespread adoption of energy efficient portable classrooms in school districts nationwide.

The experiences working on the energy efficient portable were instructive, particularly in the identification of flaws in portable classroom design. The difficulties that BAIHP staff encountered demonstrate the importance of well-defined commissioning protocols, documentation, and coordination among all personnel that service and install HVAC equipment.

Findings:

• Portable classrooms in the Pacific Northwest are occupied about 1225 hours per year, or about 14% of the total hours in a year.
• The average number of occupants in the standard 28’ x 32’ portable classroom provide an internal heat of about 480 kWh/year, or 8% to10% of space heating requirements.
• Most of the heat loss in portable classrooms manufactured after 1990 occurs by air leaking through the T-Bar dropped ceilings, because they have no sealed air/vapor barrier. This newly created phenomenon occurred with the incorporation of the less expensive dropped T-Bar ceiling in place of the more expensive sheet rock used in older portables. Air leakage also is increased because of unsealed marriage lines - now used as a low cost method of meeting the state attic ventilation requirements.
• Since all portables tested in the project used a simple seven-day programmable thermostat, the HVAC systems operate during vacations and holidays.
• Energy codes in Washington, Oregon, and Idaho are high enough to make beyond-code envelope measures non cost-effective.
• Older portable classrooms under removal consideration could be retrofitted with new energy efficiency measures at much less cost than purchasing a new portable classroom. Installing low-E, vinyl framed windows, insulated doors, T-8 light fixtures, and caulking and sealing air leaks can all be cost-effective when refurbishing older portable classrooms. HVAC system replacement in older portable classrooms will be the biggest single cost item, ranging from $4500 to $6500.
• CO 2 sensors appear to be unreliable as a control strategy. Those installed by field crews and monitored by dataloggers in this study did not match the readings shown by the CO 2 sensors which controlled the ventilation systems.

Based on data analysis from years one through four, the following measures were recommended. New portable classroom procurement, setup, and commissioning as well as existing classroom retrofit guidelines produced by the BAIHP study can all be found in Appendix A.

Recommendations:

• Install 365 day programmable thermostats in all existing portables and specify these thermostats for new construction.
• In portable classrooms constructed with T-Bar dropped ceilings, install an air/vapor barrier above the T-Bar system on the warm side of the insulation. Completely seal all edges and overlaps.
• If roof rafter insulation is used, seal the marriage line at the roof rafter joint with approved sealant such as silicon caulk or foam. Make sure there is adequate ventilation between the insulation and the roof.
• Conduct an audit of older portables scheduled for disposal to determine if retrofitting would be more cost effective than purchasing a new unit.
• Install occupancy sensors to control the ventilation system.
• Specify that new portables contain windows on opposing walls.
• Specify that new portable units contain exhaust fans on the opposite side of the classroom from the fresh air supply.

School Partnerships

Figure 52 64Energy efficient portable classroom at Pinewood Elementary School in Marysville, Washington

Figure 53 Graph comparing heating system use of the Pinewood control portable (P2-Blue) with the energy efficient portable (P5-Red). Note the energy efficient portable’s high energy use during the Christmas holidays due to incorrectly configured heating system controls.

Figure 54 Ventilation system testing at North Thurston School District.

An 895 ft 2 portable classroom (P5) was sited at the Pinewood Elementary School in Marysville Washington in August 2000. This unit exceeded current Washington State Energy Code standards with upgraded insulation in the floor, roof and walls, low-E windows, and a sensor-driven ventilation system that detects volatile organic compounds (VOCs). A second portable, built in 1985, and also located at Pinewood Elementary (P2), served as the control unit. (Figure 52.)

Energy use comparisons of the two classrooms show that the energy efficient portable used considerably more energy than the control portable. This was attributable to several factors:

• Incorrect wiring of the exhaust fan, causing it to run continually. The fan was rewired in 2000 during the summer break. Once corrected, energy use in the portable declined.
• Incorrect programmable thermostat settings which were not programmed to turn the heating and cooling system off during holidays and vacations. Though energy use was reduced when the portable was unoccupied, use was still excessive (Figure 53).
• Higher air leakage in the energy efficient portable than the control portable. Blower door testing found 19
  ACH at 50 Pa in the energy efficient classroom compared to nine ACH at 50 Pa in the control classroom. Follow-up blower door, smoke stick, and APT pressure tests indicated that the predominant leakage path tracked through the T-bar ceiling and into the vented attic due to an ineffective air barrier in the energy efficient portable. The control portable contains taped ceiling drywall.
• No initial HVAC commissioning by the HVAC supplier or the school district.
• Significant HVAC system alterations (including rewiring, ventilation system VOC sensor replacement with a CO 2 sensor, and modifications to other aspects of the HVAC control system) during 2001 by maintenance staff and the HVAC supplier, unbeknownst to BAIHP staff. Calibration testing done by scientists at the Florida Solar Energy Center on the CO 2 sensors showed significant drift in output results. This made data collected virtually unusable.
• The use of plug-in electric heaters during the winter of 2001 by the resident teacher because of room comfort problems. This led to significant room temperature variations and monitoring data showed high plug-load energy use.
• Poor fresh air flow design with the fresh air intake and exhaust fan positioned so they create a “short circuit” of fresh air, bypassing the students and teacher.

BAIHP staff proposed the following recommendations to Pinewood Elementary:

• Well-defined commissioning protocols, documentation, and coordination among all personnel that service and install the HVAC equipment. This is a critical component of efficient and healthy classroom operation and should include outside airflow rate measurements to assess adequate ventilation and control testing to insure correct system operation.
• Design changes to the portable classroom manufacturer, including the use of a structural insulated panel system (SIPS), tighter ceiling barrier and sheetrock ceilings, elimination of the vented attic, and relocation of the exhaust fan to the wall opposite the supply air vent.
• Removal of current HVAC controls and replacement with both an occupancy sensor-driven control for the ventilation system and a heating system programmable thermostat. Staff also proposed a classroom on/off switch to simplify the system turnoff during unoccupied summer and school vacations.
• Location of exhaust fans in future portables on the wall opposite the supply air vent.
• Window installation on opposing sides of the classroom to increase daylight penetration and to assist in passive cross-ventilation.

Based on the above recommendations, WSU researchers worked with Marysville school facility manager and customer representatives from Snohomish Public Utility District to assist them in setting new construction specifications for 13 portable classrooms they will procure during the next reporting period. Marysville School District will specify a completely sealed ceiling barrier, a new model heating/ventilation system, a 365 day programmable thermostat, window placement on opposite sides of the classroom, and exhaust fan placement on an opposite wall from the fresh air supply.

Washington Schools - North Thurston School District

BAIHP staff also worked with the North Thurston School District to troubleshoot a portable classroom in Lacey, Washington. (Figure 54) The classroom was experiencing high energy use and poor indoor air quality. BAIHP staff tested the classroom, made recommendations including opening the supply dampers, installing a wall side vent to better ventilate the classroom and discussed the specification development process with district staff. The North Thurston School District now is including most of the measures listed in the new procurement guidelines for their future portable classroom purchases. The school district will investigate the feasibility of installing an air/vapor above the T-bar dropped ceiling and will record costs for making these improvements.

Idaho Schools - Boise School District Retrofit

BAIHP staff located a portable classroom at the West Boise Junior High School in the Boise Idaho School District, occupied by a teacher who was interested in having the classroom monitored and retrofitted. The teacher also is an Idaho State legislator active in education issues, which staff members believe will increase the chances of implementing the final recommendations. (Figure 55)

Figure 55 Weather monitoring system installation in the Boise portable classroom.

BAIHP staff performed a baseline audit, and installed monitoring equipment to track the classroom’s energy use during 2000. In 2001, the classroom was retrofitted with an efficient HVAC system (controlled by CO 2 sensors), lighting, and envelope measures. The classroom was then reaudited, and monitored for the remainder of the year.

BAIHP staff worked with Pacific Northwest National Laboratories (PNNL) on the pre- and post-retrofit audits, and installation of the monitoring equipment. In their capacity of
providing energy management services to the school district, the local utility Avista Corporation, collected lighting and occupancy
data.

Monitoring data indicates a 58% reduction in energy usage post-retrofit. Blower door tests indicate a reduction in air leakage from nine ACH at 50 Pa to five ACH at 50 Pa. Data also revealed that heating use actually increased on weekends and holidays because of lack of internal heat gain and because the HVAC control systems are not programmed to shut off on weekends and holidays. The total retrofit cost was $9,892.

Monitored data suggests that the CO 2 sensor that controls the HVAC system is not correctly configured. The system does seem to react to an increase in CO 2 levels early in the day, but does not remain on; CO 2 levels only begin to significantly dissipate after one o'clock PM. BAIHP researchers have noted the difficulty of correctly configuring these sensors in other monitored classrooms.

Oregon Schools

Oregon BAIHP staff worked with the Portland Public School District to procure two energy efficient classrooms. These were constructed to BAIHP staff specifications and included increased insulation, high efficiency windows, transom windows for increased daylighting, a high efficiency heat pump, and efficient lighting. Staff videotaped the construction of one classroom.

Monitoring equipment was installed by PNNL staff. Estimates using the software Energy-10 indicated a total energy consumption of 9200 kWh, or $583 per year at Portland energy rates. Measured results showed the Oregon portable used about 6600 kWh for the monitored period.

Incremental costs for the energy efficiency measures were $6,705 over Oregon commercial code, including approximately $2,500 for the HVAC system. This suggests a simple payback of 10 to12 years.

Initial blower door tests found air leakage rates of 11.3 ACH at 50 Pa. BAIHP staff also identified significant leakage through the T-bar dropped ceiling and up through the ridge vents. Other monitoring results indicated that the same HVAC control problems exist with the Oregon classroom as with the others studied in this project.

The Energy Efficient model outperformed code level models in the Portland area. The older the classroom, the more energy consumed. Even when compared with new code level models from the same year, the Energy Efficient model used 35% less energy. Conventional code level classrooms do not include energy efficient measures which greatly increases the unit’s operating costs. Classrooms built more than 10 years ago, use twice as much energy as the efficient model. Those older than 20 years consume more than three times the amount of energy. From this study, researches determined that high performance classrooms can save anywhere from $200 to $1000 dollars a year in energy costs compared to older, less efficient portables.

A survey sent to teachers and maintenance staff indicates a high degree of satisfaction with the efficient portables; the teachers were most impressed with the improved indoor air quality and increased light levels due to the daylighting windows.

Historical Data Collection

In Idaho, Oregon, and Washington, BAIHP staff worked with local utilities and school districts to obtain historic energy use data on portable classrooms. This data will be used to compare energy usage from the energy efficient portables monitored in this study.

In Idaho, BAIHP staff worked with Avista Corporation's energy manager to collect historic data on 14 portable classrooms in the Boise School District. The classrooms each were equipped with discrete energy meters; as a result, BAIHP staff was able to obtain energy usage data for the past three to four years. A procedure was developed to collect information on portables at each school in cooperation with the physical facilities manager and each school lead. Historic data collection continues. Site visits and walk-through audits are planned for these 14 buildings.

• Duct Testing Data from Manufactured Housing Factory Visits

Over the past 10 years, researchers at FSEC have worked with the Manufactured Housing industry under the auspices of the U.S. Department of Energy (DOE) funded Energy Efficient Industrialized Housing Program and the Building America (BA) Program (www.buildingamerica.gov). FSEC serves as the prime contractor for DOE’s fifth Building America Team: the Building America Industrialized Housing Partnership (BAIHP) which can be found online at: www.baihp.org.

Data and findings presented here were gathered between 1996 and 2003 during 39 factory visits at 24 factories of six HUD Code home manufacturers interested in improving the energy efficiency their homes. Factory observations typically showed that building a tighter duct system was the most cost effective way to improve the product’s energy efficiency.

BAIHP and others recommend keeping duct system leakage to the outside (CFM25 out) equal to or less than 3% of the conditioned floor area, termed Qn out. However, most homes seen in a factory setting cannot be sealed well enough to perform a CFM25 out test. Results of many field tests suggest that CFM25 out will be roughly 50% of total leakage (CFM25 total). Thus, to achieve a Qnout of less than 3%, manufacturers should strive for a CFM25 total of less than 6% of the conditioned area (Qn total).

Researchers measured total duct leakage and/or duct leakage to the outside in 101 houses representing 190 floors (single wide equals one floor, double wide equals two floors, etc.). Ducts systems observed in these tests were installed either in the attic (ceiling systems) or in the belly (floor systems). Researchers tested 132 floors with mastic sealed duct systems and 58 floors with taped duct systems.

Of the 190 floors tested by BAIHP, the results break down thus:

For mastic sealed systems (n=132):

• Average Qn total = 5.1% (n=124); 85 systems (68%) achieved the Qn total ≤ 6% target.
• Average Qn out = 2.4% (n=86); 73 systems (85%) reached the Qn out ≤ 3% goal.

For taped systems (n=58):

• Average Qn total = 8.2% (n=56); 19 systems (34%) reached the Qn total ≤ 6% target.
• Average Qn out = 5.7% (n=30), more than twice as leaky as the mastic average; 5 systems (17%) reached the Qn out ≤ 3% goal.

The results show that, while it is possible to achieve the BAIHP Qn goals by using tape to seal duct work, it is far easier to meet the goal using mastic. What isn’t illustrated by the results is the longevity of a mastic sealed system. The adhesive in tape can’t stand up to the surface temperature differences and changes or the material movement at the joints and often fails. Mastic provides a much more durable seal.

Typical factory visits consist of meeting with key personnel at the factory, factory observations, and air tightness testing of duct systems and house shells. A comprehensive trip report is generated reporting observations and test results, and pointing out opportunities for improvement. This is shared with factory personnel, both corporate and locally. Often, a factory is revisited to verify results or assist in the implementation of the recommendations.

The most commonly encountered challenges observed in the factories include:

• Leaky supply and return plenums
• Misalignment of components.
• Free-hand cutting of holes in duct board and sheet metal.
• Insufficient connection area at joints.
• Mastic applied to dirty (sawdust) surfaces.
• Insufficient mastic coverage.
• Mastic applied to some joints and not others.
• Loose strapping on flex duct connections.
• Incomplete tabbing of fittings.
• Improperly applied tape

Duct system recommendations discussed in this report include:

• Set duct tightness target Qn equal to or less than 6% total and 3% to outside.
• Achieve duct tightness by properly applying tapes and sealing joints with mastic
• Accurately cut holes for duct connections
• Fully bend all tabs on collar and boot connections
• Trim and tighten zip ties with a strapping tool
• Provide return air pathways from bedrooms to main living areas

Summary of BAIHP Approach to Achieving Tight Ducts in Manufactured Housing:

• Set goal with factory management of achieving Qnout<=3% using Qntotal<=6% as a surrogate measurement while houses are in production.
• Evaluate current practice by testing a random sample of units
• Report Qntotal and Qnout findings; make recommendations for reaching goals
• Assist with implementation and problem solving as needed
• Evaluate results and make further recommendations until goal is met
• Assist with development of quality control procedures to ensure continued success

Finally, duct tightness goals can be achieved with minimal added cost. Reported costs range from $4 to $8. These costs include in-plant quality control procedures critical to meeting duct tightness goals.

Achieving duct tightness goals provides benefits to multiple stakeholders. Improving duct tightness diminishes uncontrolled air (and moisture) flow, including infiltration of outside air, loss of conditioned air from supply ducts, and introduction of outside air into the mechanical system. Uncontrolled air flow is an invisible and damaging force that can affect the durability of houses, efficiency and life of mechanical equipment, and sometimes occupant health. With improved duct tightness, manufacturers enjoy reduced service claims and higher customer satisfaction, while homeowners pay lower utility bills, breathe cleaner air, and have reduced home maintenance.